Arctic Sea Ice : Forum

Cryosphere => Arctic sea ice => Topic started by: Archimid on March 15, 2017, 11:17:17 PM

Title: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 15, 2017, 11:17:17 PM
A user posted this paper over the Melting Season thread. I want to say something about it but I don't want to derail the melting season this paper discussed. This is the discussion so far:

Does anyone have any comments on the paper that came out on Monday in Nature Climate Change, "Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice". http://www.nature.com/nclimate/journal/vaop/ncurrent/abs/nclimate3241.html (http://www.nature.com/nclimate/journal/vaop/ncurrent/abs/nclimate3241.html)

The authors propose that a substantial amount of the recently observed summer decline in Arctic Sea Ice has been driven by natural variation in atmospheric circulation. "The Arctic has seen rapid sea-ice decline in the past three decades, whilst warming at about twice the global average rate. Yet the relationship between Arctic warming and sea-ice loss is not well understood. Here, we present evidence that trends in summertime atmospheric circulation may have contributed as much as 60% to the September sea-ice extent decline since 1979. A tendency towards a stronger anticyclonic circulation over Greenland and the Arctic Ocean with a barotropic structure in the troposphere increased the downwelling longwave radiation above the ice by warming and moistening the lower troposphere. Model experiments, with reanalysis data constraining atmospheric circulation, replicate the observed thermodynamic response and indicate that the near-surface changes are dominated by circulation changes rather than feedbacks from the changing sea-ice cover. Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30–50% of the overall decline in September sea ice since 1979."

Does anyone have any comments on the paper that came out on Monday in Nature Climate Change

I have a whole article on the topic, albeit with the emphasis thus far on the reporting of the paper rather than the substance of it:

http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/ (http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/)

Quote
All this excitement in the Twittosphere and elsewhere leads one to wonder whether Ding, Schweiger et al. saw (or should have seen?) all this coming, and if so what might have been done differently? In any event this story is set to run and run and run and……

Went to look, and sure enough, this is a featured paper at WUWT where it's being sold as confirming natural cycles are responsible, not anthropogenic causes.

Expect to get repeatedly battered by deniers with this paper.  They've been given their marching orders.

See up thread for comments.   
Title: Re: Arctic sea ice changes: Natural variation vs Human influence.
Post by: Neven on March 15, 2017, 11:51:06 PM
Below the Carbon Brief article (https://www.carbonbrief.org/humans-causing-up-to-two-thirds-arctic-summer-sea-ice-loss-study-confirms), I have commented:

Quote
"The changes in atmospheric circulation in the Arctic, thought to originate in the tropical Pacific, increase the amount of water vapour in the lower atmosphere, the paper explains.  Together with a shift to fewer clouds, this has increased the amount of solar radiation reaching the ice."

So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss? Is it controlled by the PDO or ENSO?

I thought the high pressure was moving over Greenland because that's the only place cold enough for it to form (Cold Pole)?

I'm also not sure about the shift to fewer clouds, as there's an increase in water vapour over the Arctic, coming from lower latitudes and from the Arctic Ocean itself, because of Arctic sea ice loss. In fact, increased cloudiness in autumn and winter (especially these past two winters) are causing record low maximums, this year for both extent and volume.

All in all, I feel that this is all very theoretical and these scientists aren't paying enough attention to what is happening on the ground. We may have passed the point where our knowledge on the Old Arctic has become moot.

This is a non-story, because no one has said that all of Arctic sea ice loss is 100% caused by AGW*. It might be, but we can't know for sure. It might even be more than 100% if natural variation would otherwise have caused the ice to grow. We don't know. But we do know for sure that the AGW influence is not zero.

Now, if climate risk deniers are acknowledging that 60% of Arctic sea ice loss is due to AGW, they are also acknowledging that this might be killing Chinese people (https://www.theguardian.com/environment/2017/mar/15/airpocalypse-smog-events-linked-to-global-warming-research-reveals), which in essence means they are no longer climate risk deniers. If they keep lying to their fellow human beings about AGW, they are in fact extra responsible for killing Chinese and many other people. I'm sure they see it differently. And if they didn't, they probably wouldn't care.

* There are a number of papers out there looking at the influence of the AMO and the PDO, etc. Or read this blog post (http://neven1.typepad.com/blog/2012/11/climatedialogue-a-new-initiative.html) I wrote 4 years ago about Judith Curry, Walt Meier and Ron Lindsay agreeing on the anthropogenic component of Arctic sea ice loss.

BTW, thanks a lot for opening this separate thread, Archimid!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Tigertown on March 16, 2017, 12:53:04 AM
RS had a pertinent post in this regard recently and it referred to this conversation on Youtube. A little long btw, so maybe get some popcorn or something.

Dr. Richard Alley, Dr Michael Mann, and Dr Johnathan Brockopp discuss the extent of the global warming crisis without false equivalency given to climate change deniers. Video source: Conversations — Live Climate Change.

Quote
“We actually have high confidence that the warming that is happening now is not natural cycle. If anything, over the past few decades, nature has tried to cool us off a little bit… The sun has dimmed just a little bit. We have blocked the sun with particles from our smokestacks just a little bit. And yet it has warmed. If you were to ask how much of the warming that we see recently has been caused by our greenhouse gasses, it’s a little more than all of it (emphasis added).” — Dr Richard Alley

https://www.youtube.com/watch?v=l2yclMcDroQ (https://www.youtube.com/watch?v=l2yclMcDroQ)
Title: Re: Arctic sea ice changes: Natural variation vs Human influence.
Post by: Archimid on March 16, 2017, 01:32:51 AM
First (my emphasis)



The authors propose that a substantial amount of the recently observed summer decline in Arctic Sea Ice has been driven by natural variation in atmospheric circulation.

At least in the abstract, the authors of the original paper never claim anything related to natural variation. The authors only speak about atmospheric circulation variation. Whether that atmospheric circulation variation has changed due to human changes does not seem to be addressed by the paper.


From what I understand from this paper, their models held atmospheric circulations constant and varied the rest of the model. The result was that they obtained only a fraction of the melting. To me, that means that atmospheric circulation is a more influential factor than whatever variables they varied on their model. That is important, specially when they can quantify the proportion between atmospheric impact and the impact of the rest of their model. 

It is interesting that in your link there is an "associated link" to the top right hand corner :


Climate variability: Natural causes of Arctic sea-ice loss
 http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3254.html (http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3254.html)

I'll quote the only thing I can access there:

"Arctic sea-ice cover has declined precipitously in recent decades. Now research suggests that a sizable fraction of this observed historical decline could have been caused by internal climate variability rather than by human-induced warming."

The abstract seems to conflate "climate variability"  with "natural variability". Those are two very different things. There is no such thing as natural variability anymore. There probably hasn't been for decades. The current climate variability is already heavily influenced by human induced warming. The warmer it gets the larger the departure from natural variability.


BTW, thanks a lot for opening this separate thread, Archimid!


I am glad to be of a small help. Opening threads is a little daunting because it may seem rude to some, but it seems to me like it is a good way to not lose important information while keeping the thread discipline needed to keep information compartmentalized. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 16, 2017, 02:26:53 AM
Thanks to Archimid for setting up this discussion thread on Arctic Sea Ice Changes: Natural Variation vs Human Influence.

It appears that Ding et al, 2017. “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice”. Nature Climate Change.  is an important paper that addresses the widely recognized issue that the observed decline of Arctic Sea Ice is not projected by existing models. It further appears that this paper will stimulate a lot of discussion. Thus, opening a new thread to discuss this topic is useful.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 16, 2017, 02:41:14 AM
Just a short note, there were several ‘stories’ about Ding et al. that perhaps provide some useful background: “Up to half of Arctic melting can be explained by natural changes”, Christian Science Monitor; http://www.csmonitor.com/Environment/2017/0314/Up-to-half-of-Arctic-melting-can-be-explained-by-natural-changes (http://www.csmonitor.com/Environment/2017/0314/Up-to-half-of-Arctic-melting-can-be-explained-by-natural-changes)

“Natural Environmental Swings Cause Up To Half Of Arctic Sea Ice Loss”; http://www.npr.org/sections/thetwo-way/2017/03/14/520104348/natural-environmental-swings-cause-up-to-half-of-arctic-sea-ice-loss (http://www.npr.org/sections/thetwo-way/2017/03/14/520104348/natural-environmental-swings-cause-up-to-half-of-arctic-sea-ice-loss)

“Arctic Sea Ice Melt, Driven by Global Warming, Accelerated by Nature”; https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science (https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 16, 2017, 02:48:18 AM
Just one more comment; perusing the blogosphere, Stoat has made a relevant comment, “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice?”

http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/ (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/)

btw, check out this link to see the data, ie. click on 'PDF as submitted', in the first paragraph.


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Pmt111500 on March 16, 2017, 04:18:12 AM
 ::) i wonder if they include continental drift in natural variation?  ;) 8) :P thanks for the link to stoat and the paper, always nice to see scientific papers without paywall. I haven't read it yet, but admit that arctic amplification is not entirely anthropogenic. Of course the usual suspects take this on a ride. Wouldn't be surprised if the study does not say what the usual suspects say it says.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 16, 2017, 04:48:34 AM
3 links

All of them suffer the same flaw. They equate natural variation of different positive and negative forcings with the variation of atmospheric patterns.  That is not the same thing at all. Let me put it this way

It is true if you say: Arctic volume loss is 60% due to changes in atmospheric patterns.
It is false if you say: Arctic volume loss is 60% due to natural variation.


From one of your links:
Quote
The group concludes that "decadal trends in the hemispheric circulation are an important driver of Arctic climate change, and therefore a significant source of uncertainty in projections of sea ice,

Decadal trends in hemispheric circulation are also affected by global warming.


This looks to me like a concerted effort to remove human guilt for current and future Arctic conditions. Too bad that won't change the outcome. Humans are 100% responsible for the current record low Arctic conditions. If it was up to natural variation the arctic would be experiencing record growth.


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 16, 2017, 04:51:56 AM
Basically they are saying that the reason why the Arctic ice is melting faster than model predictions is due to a variation in circulationt, with increased high pressure over Greenland.  This change in circulation matches observations, and when the models are forced into this circulation change the modelled sea ice matches observations.  This seems to be strong evidence (maybe not conclusive)  that the increased sea ice melt is due to this circulation change, and is not due to loss of ice structure/strength, or a failure to include enough albedo effects, or failure to account for warming from the oceans below or mixing of the halocline.

The question then is whether the circulation change is a feedback to the ice loss, or to some other aspect of AGW.  They argue that it is not as the models do not show the circulation change.  However perhaps the models are missing a factor whereby AGW or ice loss leads to this circulation change. 

The final key would be to understand what is causing this circulation change.  If it is a naturally driven variation then presumably someone can uncover the mechanism by which this variation is driven over a multi-decadal period, similar to how we currently understand much of the mechanisms of how ENSO works, and some behind PDO and AMO (but a lot of gaps in our knowledge there IMO).  Until we understand this variation better it would remain possible that it is AGW forced in some way that the models cannot currently capture.

I'm sure this isn't the last word on research into the model-observation gap for Arctic ice loss.  I would note that all the research I am aware of on this topic does point to natural variation being the cause.  Is anyone aware of any research providing evidence otherwise?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 16, 2017, 05:04:02 AM
Basically they are saying that the reason why the Arctic ice is melting faster than model predictions is due to a variation in circulationt, with increased high pressure over Greenland.  This change in circulation matches observations, and when the models are forced into this circulation change the modelled sea ice matches observations.  This seems to be strong evidence (maybe not conclusive)  that the increased sea ice melt is due to this circulation change, and is not due to loss of ice structure/strength, or a failure to include enough albedo effects, or failure to account for warming from the oceans below or mixing of the halocline.

The question then is whether the circulation change is a feedback to the ice loss, or to some other aspect of AGW.  They argue that it is not as the models do not show the circulation change.  However perhaps the models are missing a factor whereby AGW or ice loss leads to this circulation change. 

The final key would be to understand what is causing this circulation change.  If it is a naturally driven variation then presumably someone can uncover the mechanism by which this variation is driven over a multi-decadal period, similar to how we currently understand much of the mechanisms of how ENSO works, and some behind PDO and AMO (but a lot of gaps in our knowledge there IMO).  Until we understand this variation better it would remain possible that it is AGW forced in some way that the models cannot currently capture.

I'm sure this isn't the last word on research into the model-observation gap for Arctic ice loss.  I would note that all the research I am aware of on this topic does point to natural variation being the cause.  Is anyone aware of any research providing evidence otherwise?

Michael Hauber,

I agree. You have identified a key point. Assuming that a circulation change is driving Arctic Sea Ice melt, is this circulation change a natural variation, or rather,  a change due to external factors?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 16, 2017, 05:46:14 AM
That is, assuming that an atmospheric circulation change has been an important contributor to the observed reduction in Arctic Sea Ice, is this hypothetical atmospheric circulation change a natural variation or is this proposed circulation change itself a result of climate change?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: gerontocrat on March 16, 2017, 11:42:17 AM
The paper seems to say that they took out the change to atmospheric circulation to see the change in sea ice caused by AGW alone. But did they run the model again taking out AGW to see the change in sea ice when only change in atmospheric circulation is included ?

And if they did, did adding the reduced effect from each model run = the total observed change in sea ice?
I doubt it - in all the models on any subject I have made there is a multiplier effect. It is also surely dangerous to assume cause and effect in a uni-directional manner. Models usually use iteration which implies changes in parameters cause changes in other parameters which in turn..

However, I will not be surprised if Jim Hunt is writing about climate-gate-3 after this weekend's Breitbart News and Daily Mail.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 16, 2017, 02:16:33 PM
This looks to me like a concerted effort to remove human guilt for current and future Arctic conditions.

Why do you believe Axel Schweiger (PIOMAS) or Eric Steig would sign on to any paper with that objective?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 16, 2017, 02:38:46 PM
Why do you believe Axel Schweiger (PIOMAS) or Eric Steig would sign on to any paper with that objective?

Sorry ktonine, I should have been more explicit. I don't think the authors of the original paper are acting with malice. The original paper seems to me like good science. However, the secondary articles that reference the original paper and are conflating atmospheric variability with natural variability are the by product of malice or ignorance from the science communicators.

I think the malice (or ignorance) started with Neil Swart  in this article http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3254.html (http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3254.html)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 16, 2017, 03:11:20 PM

The question then is whether the circulation change is a feedback to the ice loss, or to some other aspect of AGW.  They argue that it is not as the models do not show the circulation change.  However perhaps the models are missing a factor whereby AGW or ice loss leads to this circulation change. 

The final key would be to understand what is causing this circulation change.  If it is a naturally driven variation then presumably someone can uncover the mechanism . . . Until we understand this variation better it would remain possible that it is AGW forced in some way that the models cannot currently capture.

Michael Mann and Alex Schweiger had a brief exchange on twitter:  https://twitter.com/MichaelEMann/status/841362467603255298 (https://twitter.com/MichaelEMann/status/841362467603255298)

the crux: 
Quote
(Michael Mann): But misfit relative to CMIP5 mean doesn't imply internal variability! CMIP5 mean likely does NOT capture true forced trend.

Magical Thinking


summary:  This is the most egregious example of placing the entire world at risk through protecting personal self-interests that I have ever seen from reputable scientists (read: not paid climate deniers) and shows that, just because you are a scientist, you are not necessarily a good or even a moral person.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: epiphyte on March 16, 2017, 03:22:35 PM
The paper seems to say that they took out the change to atmospheric circulation to see the change in sea ice caused by AGW alone.

Brilliant. Perhaps they should take out the atmosphere altogether. Then they could observe that daytime would be hot enough to boil water, and at night it would be cold enough to freeze CO2. 

...and humans would plainly have nothing to do with it!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 16, 2017, 03:39:58 PM
Perhaps I might once again direct the attention of one and all to Michael Mann's Twitter discussion with Axel Schweiger and Eric Steig:

http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#Scientists (http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#Scientists)

as well as my own initial question?

http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#Q1 (http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#Q1)

Quote
All this excitement in the Twittosphere and elsewhere leads one to wonder whether Ding, Schweiger et al. saw (or should have seen?) all this coming, and if so what might have been done differently?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 16, 2017, 04:36:42 PM
summary:  This is the most egregious example of placing the entire world at risk through protecting personal self-interests that I have ever seen from reputable scientists (read: not paid climate deniers) and shows that, just because you are a scientist, you are not necessarily a good or even a moral person.

jai - have you read the full paper?

I don't think so.  If you did you are neglecting the many caveats, for instance:

Quote
This conclusion assumes that the CESM accurately reflects the response of the high latitude circulation to anthropogenic forcing. Attribution estimates of Arctic sea ice loss based on CESM therefore need to be viewed with caution.

In addition, it is important to recall that we have used reanalysis data as a proxy for observational data. Reanalysis products are reliable representations of the observed circulation humidity and temperature, but less so for cloudiness. The variability in total cloud cover in the satellite data is well represented in the reanalysis data seems, particularly in summer. However, there is evidence that the relationship between sea ice and the vertical distribution cloud fraction in reanalysis does not agree well with that in observations. Therefore, to the extent that changes in cloudiness contribute to the DLR trends associated with the trends in circulation, the connection between large-scale circulation and cloud variability is subject to considerable uncertainty and needs to be explored in future studies. We also must consider the limitations in the design of our experiment (Exp-5), which constructs atmospheric forcing fields based on a linear regression of a Z200 index, to quantify the circulation impact on sea ice loss

As to the CMIP5 criticism, isn't that covered right in the abstract?

Quote
Because the observed circulation variability over the Arctic is inconsistent with the expected model response to anthropogenic forcing, a significant component of sea ice loss over the last three decades may have been driven by dynamical sources of natural climate variability

CMIP5 represents the expected model response to AGW.  Observations disagree.  Models wrong, observations wrong, results due to other than anthropogenic forcing?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 16, 2017, 05:38:45 PM
Their assertions are not substantiated by their claims, caveats be damned.  This is a CYA paper and should be viewed as such.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 16, 2017, 07:36:46 PM
Come on, this isn't a CYA paper. It's a genuinely interesting subject. which wouldn't have garnered nearly as much as attention, if it hadn't been spun and, like Archimid says, most so by that Nature article preview.

The fact is that this just isn't all that exciting. First of all, no one has ever said that all of recent Arctic sea ice loss is caused by AGW. Not because it isn't, but because we can't know for sure (although the downward trend definitely wouldn't be so steep if it wasn't for AGW). Secondly, there have been many more papers trying to pin down the amount of human attribution as compared to the AMO, the PDO, etc.

Climate risk deniers are dumb to spin this, because it automatically means they acknowledge the climate is changing. And Arctic sea ice loss is most probably just going to continue, especially if that 60% figure is wrong (which it might very well be), and so the consequences of this loss will become ever clearer.

Climate risk deniers are sad, old, selfish, white men with an authoritarian streak. It's best to ignore them, and not get worked up too much.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 16, 2017, 08:13:52 PM
Quote
Even more reprehensible is that when the arctic DOES melt out so much earlier (with devastating global consequences) this paper, with its selfishness and unscientific assertions will be used to allay the global response to the climate emergency, reducing the effectiveness of our collective response to the crisis

I guess you are right Neven, it is impossible to say if this is a CYA paper from entrenched arctic scientists who have dedicated their lives to learning and teaching about these things or if their unsubstantiated interpretations of global atmospheric circulations being 'natural' even though recent studies indicate a significant anthropogenic component (due to many feedbacks, ENSO impacts and aerosol impacts) are rather based on institutional thinking, bias toward confidence in their previous work (models), failure on the SLD (Side of Least Drama) and trying to find a reason an explanation why their models are so pathetically, horribly, dis-servingly off base.

In any event, I assert that, once the arctic melts out (and I have said very clearly that I expect this to happen in the next 2 to 6 years) I can guarantee you that we will hear this paper referenced by those who want to do little or nothing in the way of climate mitigation (as we already are).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 16, 2017, 11:13:24 PM
I think it is important to clearly define "natural variability".

If the definition of "natural variability" is variability that has not been influenced by humans, then the conclusion is BS.

If the definition of "natural variability" is the variability beyond the scope of this model like maybe ENSO, solar cycles, PDO/AMO, snow cover or any other mayor natural phenomena,  then the conclusion is correct. It just need to be clear that in that case "natural variability" is being influenced by humans.

In any event, I assert that, once the arctic melts out (and I have said very clearly that I expect this to happen in the next 2 to 6 years) I can guarantee you that we will hear this paper referenced by those who want to do little or nothing in the way of climate mitigation (as we already are).

I don't think once the Arctic melts there will be a blame game. I think we will be too busy trying to survive for that. Even if there is, fossil fuel interests are already very well positioned to forgive themselves for any wrong doing including the genocide their fraud and deceit will bring. Justice will be served by mother nature. She can be ruthless.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 16, 2017, 11:22:26 PM
Humans have affected "natural variability" since the dawn of agriculture if not much earlier - e.g. by killing off the mega fauna. ENSO , QBO, MJO, volcanoes etc are all part of natural variability. There is no natural variability without those...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 16, 2017, 11:52:19 PM
Humans have affected "natural variability" since the dawn of agriculture if not much earlier - e.g. by killing off the mega fauna. ENSO , QBO, MJO, volcanoes etc are all part of natural variability. There is no natural variability without those...

We have indeed affected  earth systems since the begining of history. But after the energy use explosion of the 1800 that influence grew tremendously.

Attached is a screenshot of a you tube video that illustrates perfectly human influence on all  of earth's naturally variable systems. I think it can be argued that for the first few thousand years AGW was very good for humanity. But right now, it is a case of too much of a good thing.

If anyone has a better sample of that image could you post a link for it?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 17, 2017, 12:13:37 AM
'It is widely believed that the decline in Arctic sea ice coverage for the past three decades
is due to increasing greenhouse gases, yet the mechanisms of this linkage are not well
understood. Here, we present observational and modeling evidence that the rapid melting
of summertime sea ice was due to changes in the large-scale atmospheric circulation during
the Northern Hemisphere summer'

While the overall thrust of the paper is worthwhile and interesting research, the opening lines seem written to maximise the potential for misleading headlines about a new paper proving that the Arctic ice loss is due to natural variation and not CO2.  Perhaps it was written to be deliberately controversial to garner more attention and citations.  Is it possible that a paid denier could infiltrate a group of otherwise solid scientists with the purpose of such wording.  I know this isn't the first time I've seen a research paper where the bulk of the work seemed reasonable and sensible but the abstract/conclusion/intro seemed written in a manner to maximise the opportunity for false reporting.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 17, 2017, 12:24:27 AM
Is it possible that a paid denier could infiltrate a group of otherwise solid scientists with the purpose of such wording.

Well, if you're into conspiracy theories then there is speculation at Stoat about the lead author's links to Big Willie Soon:

http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58437 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58437)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 17, 2017, 12:46:22 AM
About the paid deniers and conspiracy theorists I'll quote AbruptSLR's quote of Tolstoy's War and Peace

Quote
"At the advent of danger there are always two voices that speak with equal force in the human heart: one very reasonably invites a man to consider the nature of the peril and the means of escaping it; the other, with a still greater show of reason, argues that it is too depressing and painful to think of the danger since it is not in man's power to foresee everything and avert the general march of events, and it is better therefore to shut one's eyes to the disagreeable until it actually comes, and to think instead of what is pleasant. When a man is alone he generally listens to the first voice; in the company of his fellow-men, to the second."

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 17, 2017, 05:34:11 AM
archimid,

the linked image is derived from the following ruddiman image which was published in 2007 full paper here:  http://onlinelibrary.wiley.com/doi/10.1029/2006RG000207/full (http://onlinelibrary.wiley.com/doi/10.1029/2006RG000207/full)

The image you posted is a combination of this ruddiman image and a combination graphic published on Skeptical Science here:  https://www.skepticalscience.com/the-two-epochs-of-marcott.html (https://www.skepticalscience.com/the-two-epochs-of-marcott.html)

the image you are looking for is from this original Ruddiman paper (2016): http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/59400/RuddimanLateHoloceneClimate.pdf?sequence=1 (http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/59400/RuddimanLateHoloceneClimate.pdf?sequence=1) 

larger image here: https://pbs.twimg.com/media/CX-UqGpWYAAgnI_.png (https://pbs.twimg.com/media/CX-UqGpWYAAgnI_.png)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 17, 2017, 12:34:49 PM
freaking awesome. thank you jai mitchell!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 17, 2017, 01:05:52 PM
Expert reaction to research on natural climate variability and Arctic summer sea ice  (http://www.sciencemediacentre.org/expert-reaction-to-research-on-natural-climate-variability-and-arctic-summer-sea-ice/)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on March 17, 2017, 01:18:23 PM
Expert reaction to research on natural climate variability and Arctic summer sea ice  (http://www.sciencemediacentre.org/expert-reaction-to-research-on-natural-climate-variability-and-arctic-summer-sea-ice/)
This resonates well with my thinking. Most other responses accept that the variability is natural without question.
Quote
Prof. Jeffrey Kargel, Glaciologist at the University of Arizona, said:

“This new work by Qinghua Ding and others – involving an analysis of the observational record of sea ice and numerical model testing to root out the causes of long-term decline and yearly variations in Arctic sea ice – does well to explain links between long-term weather in the Arctic and year-to-year variations in sea ice on the same time frame.  In other words, weather and sea ice melting and sea ice extent are connected, and Arctic weather is connected to weather elsewhere in the world, even as far away as the tropical Pacific Ocean.

“The already well-established, if imperfectly known, many-decades-long climatic connections to human root causes of the decline in sea ice are not this paper’s focus. Even so, these authors’ and others’ work shows that burning of fossil fuels is having a large direct impact in contributing to rapid sea ice declines. This paper does well to explore the effects on Arctic sea ice of year-to-year variations in Arctic and global long-term weather.  The paper does less well to explore how the ‘weather’ part of the variations are also connected indirectly– partially– to rising greenhouse gas abundances.

...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 18, 2017, 01:30:55 AM
Just a few comments regarding Ding et al, 2017; “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice” and also the discussion of this paper.

First, a PDF of the paper can be found here: https://www.atmos.washington.edu/~david/Ding_etal_2016_submitted.pdf (https://www.atmos.washington.edu/~david/Ding_etal_2016_submitted.pdf)

Given that Nature Climate Change is a well-respected high profile journal with a rigorous peer review system, it appears that this paper is potentially important. The observed rapid decline of the Arctic Sea Ice is not explained by current hypotheses. Thus, there is a need for new ideas.

I do not agree with the notion that the scientists who did this work have motives other than advancing climate science. I further do not agree that the scientists who study this topic lack insight and creative thinking.

Regarding ‘models’ I have a somewhat different understanding than what is commonly expressed about models. I view climate models as hypotheses. Given that scientific understanding is inherently tentative and incomplete, of course these models (hypotheses) have limitations. The point is to pursue the scientific method. With a complex system like the geophysics of the Arctic, computational simulations of recognized processes makes sense.

As many have reiterated, the observed rapid decline of Arctic Sea Ice is not explained by present understanding of the function of the climate system. New insight is required.  “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice” appears to be an interesting contribution to the discussion.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on March 18, 2017, 01:39:56 AM
As many have reiterated, the observed rapid decline of Arctic Sea Ice is not explained by present understanding of the function of the climate system. New insight is required.  “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice” appears to be an interesting contribution to the discussion.
I agree, and admit I haven't digested the paper in detail yet, but am skeptical that some/much of what they attribute to "natural variation" which may actually be driven by climate change outside of the Arctic.  More later after I've done due diligence.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 18, 2017, 02:00:21 AM
jdallen

I agree that you have recognized a key point, "I agree, and admit I haven't digested the paper in detail yet, but am skeptical that some/much of what they attribute to "natural variation" which may actually be driven by climate change outside of the Arctic."

Michael Hauber made this same point in the discussion above. If a circulation change is promoting the melt of the arctic sea ice, is this circulation change a natural variation, or is this circulation change the result of human activity?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: misanthroptimist on March 18, 2017, 03:30:48 AM
jdallen

I agree that you have recognized a key point, "I agree, and admit I haven't digested the paper in detail yet, but am skeptical that some/much of what they attribute to "natural variation" which may actually be driven by climate change outside of the Arctic."

Michael Hauber made this same point in the discussion above. If a circulation change is promoting the melt of the arctic sea ice, is this circulation change a natural variation, or is this circulation change the result of human activity?
I think that that is the big question. I've only seen the abstract, so perhaps the full paper explains this better.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 18, 2017, 11:42:56 AM
I've only seen the abstract, so perhaps the full paper explains this better.

Please see:

http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#PDF (http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#PDF)

Please also scroll down a bit, then follow the instructions:

http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#Mar-18 (http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#Mar-18)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 18, 2017, 12:01:00 PM
Like many medical studies... unable to separate cause and effect from correlated effects. Asking the right question is often harder than highlighting the obvious but wrong corellation...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 18, 2017, 01:23:06 PM
tzupanic, thanks for the paper.  Here is a quote from the paper:

Quote
Having attributed a substantial part of September sea ice decline to variability in the high
latitude circulation during the preceding summer, we now examine whether long-term changes in
the circulation are driven by natural or anthropogenic variability. Upper tropospheric circulation
change in the Arctic is subject to strong natural variability originating from the tropics.
Previous research identified a relationship between tropical SST variability and annual mean
atmospheric circulation over the Arctic with a center of action over Greenland. Model
experiments show that about 50% of the circulation change and the associated warming over
Greenland is attributable to natural variability originating from the tropical Pacific Ocean. An
“ad hoc” attribution through a combination of these components suggests that ~30% (= 50% ×
60%) of the sea ice decline observed since 1979 during JJA is attributable to natural variability in
the tropical Pacific

To this my question is, are sst's over the pacific affected by Human forcings? Well the answer is of course yes!

They attribute the changes in the atmospheric patterns to changes in the pacific, but they pretend that the changes in the pacific are natural. That's crazy talk.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 18, 2017, 02:37:57 PM
I think this paper is bad news for the ice(and us). It weakens arguments that because of the enthalpy of the Arctic the ice is safe for many more years. Particularly if the atmospheric circulations keep changing due to changes in Earth systems other than the Arctic.

I think the causation here goes multiple ways. Atmospheric currents change the ice  and changes in the ice change the atmospheric currents. The same for the atmosphere Pacific sst interaction. Changes in the atmosphere change Pacific sst's and viceversa.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: gerontocrat on March 18, 2017, 03:46:09 PM
Causation. It is a mugs' game to separate individual causations in an interdependent circular system. I am sure that this recent paper used the most rigorous methodologies. But when the answer is "42" because the question was wrong ? (Pace Douglas Adams).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Gray-Wolf on March 18, 2017, 04:20:24 PM
Don't worry Archmid the paper has nearly both feet squarely in the 'old Arctic' and it is difficult to see what actually remains of that?

This year is the earliest possible return of the perfect melt storm and would be bang on time for the two before 07' but do we really expect one???

The circulation is now far too messed with to rely on that 'old Arctic' cycle so how many other past cycles are now relegated /retired?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: epiphyte on March 18, 2017, 05:11:57 PM
Causation. It is a mugs' game to separate individual causations in an interdependent circular system. I am sure that this recent paper used the most rigorous methodologies. But when the answer is "42" because the question was wrong ? (Pace Douglas Adams).

Or even when both the question and the answer were right, but you were trying to reconcile them with the wrong set of rules.  Viz: 6x9=42   ... but only in base 13.

As Arthur Dent might say, "There must be something wrong with the Universe."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Pragma on March 18, 2017, 08:52:55 PM
Don't worry Archmid the paper has nearly both feet squarely in the 'old Arctic' and it is difficult to see what actually remains of that?

This year is the earliest possible return of the perfect melt storm and would be bang on time for the two before 07' but do we really expect one???

The circulation is now far too messed with to rely on that 'old Arctic' cycle so how many other past cycles are now relegated /retired?

I think this sums it up pretty well. Similarly, I expect the denialistas to claim that the arctic ice isn't melting, it's being blown out the Fram, ignoring the fact that the ice fragmentation and mobility didn't exist at this time of year 20+ years ago.

I am willing to give the authors the benefit of the doubt but considering how much of a hot button this is, I think they could have done a much better job of framing their position. I would have expected the peer review process to point that out.

That said, it wouldn't be the first time an academic published his findings without considering the implications in a larger world.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 18, 2017, 09:50:53 PM
Quote
That said, it wouldn't be the first time an academic published his findings without considering the implications in a larger world.

This is so unfair to the scientists. They are trained in mathemathics and science,  diciplined knowledge and  documentation not in public relations or public policy. They shouldn't have to to worry about sounding too climate change denier or too climate change alarmist. They should just do the best science they can and report it as accurately but also as clearly as possible.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on March 18, 2017, 10:44:36 PM
Bear in mind denialists, like good populist politicians, will always find something to latch onto. After all many of them are paid to do it, and the others are fervent believers in their "cause". I doubt wording it differently would make any actual difference in the world.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Pragma on March 19, 2017, 12:10:42 AM
Quote
That said, it wouldn't be the first time an academic published his findings without considering the implications in a larger world.

This is so unfair to the scientists. They are trained in mathemathics and science,  diciplined knowledge and  documentation not in public relations or public policy.

I respectfully disagree. Scientists are not a different species and they exist in academia, which is one of the most political environments there is. Every action has consequences and we all should be accountable for our actions.

To say that a scientist is exempt from the the realities of life is to just reinforce the "ivory tower" stereotype.

Oren:

I agree, but you make my point for me. It is well known that deniers will take anything even faintly ambiguous and spin it, which makes it all the more important to be clear. Just because a denier is waiting to pounce is not an excuse to not do the best one can. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: 6roucho on March 19, 2017, 12:28:01 AM
Quote
That said, it wouldn't be the first time an academic published his findings without considering the implications in a larger world.

This is so unfair to the scientists. They are trained in mathemathics and science,  diciplined knowledge and  documentation not in public relations or public policy.

I respectfully disagree. Scientists are not a different species and they exist in academia, which is one of the most political environments there is. Every action has consequences and we all should be accountable for our actions.

To say that a scientist is exempt from the the realities of life is to just reinforce the "ivory tower" stereotype.
I think Archimid means scientists aren't necessarily good at public relations or public policy, and I think that's true [even if it's a stereotype]. One reason is that science requires honesty, while public relations and public policy are both prone to gaming by the unscrupulous. If a system doesn't constrain cheating, then cheats have an advantage. Another reason is specialisation. I work in a business that has both scientists and salesmen. I'd never ask a salesman to perform research, because the result would be nonsense. For the same reason, I hate it when scientists try to do sales. There are of course individual exceptions.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Ranman99 on March 19, 2017, 12:44:31 AM
There are some people that sell solutions such as in the information communications and telecommunications field that have no legacy solutions to protect and can afford to be succinct to the point and honest and with a take it or leave it attitude.

I watched a scientist delivering a spiel to the Australian senate last year and took the fellow about 10 minutes to say what I would have said directly in 30 seconds.

As soon as a coal dust covered senator launched a lame attack back the guy crumbled and started mumbling another 10 minute almost unintelligible retort.

I personally had a come back in mind that would have stopped the guy in his tracks in 10 seconds.

There are many factors when it comes to this problem but I have seen that kind of behaviour often now in relation the the climate debate. Know your audience be ready to lay it out in terms they will understand.

When the consequences are dire and there is a sense of urgency I think one has to state the hypothesis quickly and clearly first and then go into the data.

Maybe the climate change effort needs to identify the best spokes people to speak to the public and the other parties. A what are your experiences and what are you seeing approach will start to work now as the evidence in the environment is overwhelming.

Where are the media campaigns funded by concerned philanthropists with the right spokes people.

Every day I walk down Orchard street in Singapore past every shop with no front doors and air conditioning blasting into the street to entice you in. All of South East Asia is like that with 600 million people here.

Sorry I am beginning to rant!!! ;-) Maybe it was the sales guy dig. It is the same as I used to do because I am actually a technical man originally and a sales guy by providence (accident).

Just my three cents ;-)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 19, 2017, 01:53:16 AM
Randy,

The majority of the scientists and engineers do not have the skills to be concise,  on target and quick on come backs. It is unfortunate...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Pmt111500 on March 19, 2017, 04:44:51 AM
Randy,

The majority of the scientists and engineers do not have the skills to be concise,  on target and quick on come backs. It is unfortunate...

Yep, it comes with the job description. Many, coming to science, are hoping to make a big discovery. On one short 'philosophy of science'-course I took the lecturer said on most lessons 'the first thing to doubt is yourself". There were several reiterations of this too.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: 6roucho on March 19, 2017, 04:45:03 AM
Sorry I am beginning to rant!!! ;-) Maybe it was the sales guy dig. It is the same as I used to do because I am actually a technical man originally and a sales guy by providence (accident).
It wasn't a dig, Ranman99, it was a compliment. This is veering off topic, but sales is a highly skilled activity. One you've learned to do, and good on you. Public relations is the same. When scientists try to do public relations, such as by giving interviews, they're like PR people doing experiments by putting stuff in beakers and heating it up. It may by some chance be mostly correct [e.g. they've seen it done so know roughly how to do it] but it's only scratching the surface of a highly complex process.

Again, there are individual exceptions, but even the best public intellectuals need the machinery of communications in place to change opinions. In science, this is often provided by the mainstream media. Without them, public knowledge of science would be sunk.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: MrVisible on March 19, 2017, 05:58:02 AM
Randy,

The majority of the scientists and engineers do not have the skills to be concise,  on target and quick on come backs. It is unfortunate...

Those skills take quite a bit of work to master. Debate club in college helps a lot, as does law school or a communications degree. These are people who study deceptive rhetoric the way scientists study science; it's no surprise that scientists are often outgunned in the media.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 19, 2017, 12:03:17 PM
Hello ASIF,
My first post ever here, although I am an avid reader of this forum and have great respect for the fabulous work by Neven and team. I am not a climate scientist and am just posting an opinion as a concerned citizen of the world. And the reason I am posting my very humble opinion on this precise topic is that I believe this particular paper by Ding et al makes a dangerous argument at a critical time in human history.
To summarize my opinion, I think this article begs three questions:
1) Is the argument made in the article, that the disappearance of Arctic sea ice in summer could be attributed in a large part to "natural climate variability" (that's the precise expression used in the abstract of the paper), scientifically correct?
2) I have long thought - and I think many here share the same belief - that Arctic sea ice is "the canary in the mine" (https://en.wiktionary.org/wiki/canary_in_a_coal_mine) of climate change. The article by Ding argues exactly the contrary, and as pointed out by jai mitchell above, weakens the scientific, economic and political argument that urgent and radical emissions reductions policies should be adopted ASAP, to avoid the worst effects of global warming / climate change / ocean acidification. So, is it the responsibility of scientists to avoid publishing such an article , or do scientists live in a vacuum, and can publish whatever they want whenever they feel they have a valid scientific argument?
3) Since October 2016 and up until now (mid-March 2017), we have had global sea ice extent record lows, many standard deviations below average. Clearly, this is not natural variability and even way below trend lines, not only for Arctic sea ice, but also for Antarctic sea ice. Like many here, I feel we have entered a new regime for our global climate, and this is clearly reflected in what is happening with sea ice at both poles. Or, if you prefer, the "canary in the mine" of global warming just died.
This should ring an alarm bell for climate scientists and political leaders worldwide, yet at precisely this point in time there comes an article that essentially says there is no such canary in the mine and the disappearance of Arctic sea ice is mostly attributable to "natural climate variability".
Essentially I am claiming that the timing for the publication of this article is highly suspicious. And yes, that is sort of a conspiracy theory.  :o

My opinion here, just to be clear, is that:
1) The disappearance of Arctic sea ice year round is definitely and more than 100% caused by GHG emissions from human activity. In other words, the Ding et al article is scientifically questionable.
2) No, scientists don't live in a societal vacuum and should take responsibility for the science they produce or don't produce, specially when millions of human lives are at stake. (https://en.wikipedia.org/wiki/Einstein%E2%80%93Szil%C3%A1rd_letter, James Hansen's testimony in Congress in 1988, etc)
3) Just when we have a very clear sign, evidenced by irrefutable data, of irreversible climate change attributable to anthropogenic fossil carbon emissions and at a critical time when public policies worldwide should be put in place to reduce those emissions, we have a highly questionable scientific paper that gets published dismissing this very sign of irreversible climate change as "natural variability". I find this coincidence highly improbable.

Just a few charts to support my opinions above, mainly that the disappearance of sea ice is NOT due to any kind of "natural climate variability", despite what Ding's "improved" models may show or not:
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 19, 2017, 12:43:03 PM
Welcome to the ASIF, AndrewB. Your profile has now been released.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Andre on March 19, 2017, 01:30:15 PM
Welcome, AndrewB! Nice first post to get started on the forum and hopefully not your last!

I fully agree with your main arguments. Considering the possible catastrophic climate change outcomes and the already lacklustre response of most people and governments around the world, it is crucial that everybody takes responsibility for how they present new studies, facts and evidence.

 It is more important than ever for all of us to appreciate that messaging matters and the same results, presented differently, would have evoked a very different kind of response.

As has been pointed out above, that might simply portray a lack of effective communication and PR skills and say less about any alterior motives.

However, I dont know, if we can afford to be so seemingly unskilled at effective PR much longer. The negative side effects will eventually catch up with us.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 19, 2017, 04:09:27 PM
Welcome Andrew,

I find this coincidence highly improbable.

Here's yet another "coincidence" for you to consider, extremely hot off the (literal!) presses:

"Don’t Panic! It’s Just Another Climategate 2 Correction!! (http://greatwhitecon.info/2017/03/dont-panic-its-just-another-climategate-2-correction/)"

Quote
Snow White’s very good friend Alice F. with her planet-wide patent pending hyper-sensitive wetware alternative facts detector is now on the case:
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 19, 2017, 07:34:50 PM
tzupanic, thanks for the paper.  Here is a quote from the paper:

Quote
Having attributed a substantial part of September sea ice decline to variability in the high
latitude circulation during the preceding summer, we now examine whether long-term changes in
the circulation are driven by natural or anthropogenic variability. Upper tropospheric circulation
change in the Arctic is subject to strong natural variability originating from the tropics.
Previous research identified a relationship between tropical SST variability and annual mean
atmospheric circulation over the Arctic with a center of action over Greenland. Model
experiments show that about 50% of the circulation change and the associated warming over
Greenland is attributable to natural variability originating from the tropical Pacific Ocean. An
“ad hoc” attribution through a combination of these components suggests that ~30% (= 50% ×
60%) of the sea ice decline observed since 1979 during JJA is attributable to natural variability in
the tropical Pacific

To this my question is, are sst's over the pacific affected by Human forcings? Well the answer is of course yes!

They attribute the changes in the atmospheric patterns to changes in the pacific, but they pretend that the changes in the pacific are natural. That's crazy talk.

WRT tropical humidity translation northward to the arctic I would recommend everyone read this paper thoroughly:  http://www.atmos-chem-phys.net/16/14331/2016/acp-16-14331-2016.pdf (http://www.atmos-chem-phys.net/16/14331/2016/acp-16-14331-2016.pdf)

my commentary is here: http://forum.arctic-sea-ice.net/index.php/topic,1384.msg96264.html#msg96264 (http://forum.arctic-sea-ice.net/index.php/topic,1384.msg96264.html#msg96264)

I can guarantee you that this physical reality and the consequences of China shutting down its 30 most sulfur producing coal mines and installing scrubbers is NOT considered in their model as anthropogenic but is rather attributed to 'natural variability'.

quote below: not only are powerful dynamics NOT included in the models, the spacial resolution of the models and impacts on atmospheric circulation are not competent enough to accurately project the impacts that ARE included due to regional scale impacts on atmospheric circulation

Quote
Results from general circulation models show almost no
changes in the relative humidity in a changing climate (Held
and Soden, 2000; Soden et al., 2005). However, very few
general circulation models have so far begun to include the
effects of aerosols on deep convective clouds (Boucher et
al., 2013; Khain et al., 2015). Namely, as noted by Khain
et al. (2015), the only feasible option in current general circulation
models is to use bulk microphysics parameterisation
schemes. However, bulk microphysics schemes have trouble
producing the effects of aerosols on cloud cover and cloud
top height. As a result, the effect of aerosols on UTH is
not correctly included in the current projections of climate
change produced by general circulation models. Estimates
of climate sensitivity that combine temperature observations
with estimates of greenhouse gas and aerosol-induced radiative
forcing should also be reconsidered.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 19, 2017, 07:48:18 PM
AndrewB

thank you for your cogent statements.  I have long suspected that there are factions within the scientific community that work within the normal frameworks to provide contrarian views to reduce the mitigation imperative.  For example the Barnes' paper that used cherry picking to contrast Vavrus & Barnes Francis (2013) RE: 'wavier' jet stream due to reduced temperature gradients.  Also Nordhaus' work for his entire career, the actions of his apprentice Tol on falsifying economic impacts (lower) under RCP 8.5 the list of questionable activity goes on and on it is not likely that all scientific hacks working to prevent mitigation are invited before a republican congress to publicly testify their lies.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on March 19, 2017, 10:32:03 PM
...is that I believe this particular paper by Ding et al makes a dangerous argument at a critical time in human history.
OK...What is dangerous about it, and why should he not make a dangerous argument?

My vague sense in scanning it that it is crap, but the only thing dangerous about crap are the worms which might wait within it.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on March 19, 2017, 10:35:59 PM
AndrewB, welcome and thank you for putting it so concisely. To me argument 1 is still the most important, and I find the scientific claim highly questionable. The negative arctic sea ice trend is so obvious that attributing it to variable natural causes unrelated to AGW and GHGs using a model, probably means the model is not good enough.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 19, 2017, 11:30:18 PM
My vague sense in scanning it that it is crap, but the only thing dangerous about crap are the worms which might wait within it.

Yes, because experts who have studied the subject and been at the top of their fields for a couple of decades or more are more likely to produce crap than your vague sense.

STFU already.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Andreas T on March 19, 2017, 11:55:50 PM
on the Nature site with the abstract I saw a link to this article "The missing Northern European winter cooling response to Arctic sea ice loss" http://www.nature.com/articles/ncomms14603 (http://www.nature.com/articles/ncomms14603) which is interesting. I interpret it as saying that variations (in that case the NAO) can have different effects as the background trend shifts (in that case sea ice cover).
This gave me the following idea:
In a situation where the fluctuations can reinforce the trend (sea ice loss) that may ratchet the trend into a domain in which the fluctuation in the opposite direction will have less of an effect.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Pragma on March 20, 2017, 12:17:26 AM
My vague sense in scanning it that it is crap, but the only thing dangerous about crap are the worms which might wait within it.

Yes, because experts who have studied the subject and been at the top of their fields for a couple of decades or more are more likely to produce crap than your vague sense.

STFU already.

Wow! When it comes to logical fallacies, you almost have a twofer there. First, an appeal to authority, which is to say, no argument at all. Second, your uncalled-for rudeness is very close to an ad hominem attack.

May I suggest an actual scientific discussion instead?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on March 20, 2017, 12:35:04 AM
<snip, not helpful or useful; N.>
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 20, 2017, 12:38:42 AM
May I suggest an actual scientific discussion instead?

There will be one if everyone stops jumping on each other, instead of ignoring the stuff that irritates for a while. Makes it easier for me to moderate as well.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 20, 2017, 12:56:41 AM

To this my question is, are sst's over the pacific affected by Human forcings? Well the answer is of course yes!

They attribute the changes in the atmospheric patterns to changes in the pacific, but they pretend that the changes in the pacific are natural. That's crazy talk.

Of course CO2 is impacting Pacific SSTs.  But we also know there are significant natural variations at work over multi-decadal time frames in the tropical Pacific, namely PDO.

Looking at a trend in SSTs from 1979 to 2016 in GISS (https://data.giss.nasa.gov/gistemp/maps/) shows a significant cool PDO/ENSO signal over the time period in question.  Is Co2 causing a trend towards cooler PDO/ENSO?  If so the pause may not be totally a natural variation, but rather a negative feedback on global warming.  Or is this cooling due to a  natural variation?

I've noted in the past that the fastest loss in Arctic ice loss corresponds roughly to the period of pause in global temp increase.  Could easily be coincidence, but research linking both the pause and now the Arctic ice to tropical Pacific temps suggests something more. 

Models have tended to suggest that CO2 is more likely to contribute to warmer ENSO/PDO conditions, although there seems to be variation, and I'm not yet fully convinced (I like the idea that Co2 warming would lead to cool PDO, primarily due to faster warming of surface waters than deep waters leading to a cooler ENSO tongue in comparison to rest of ocean).  Recent ENSO behaviour has been on the warmer side again and it looks like we may be back to a warm PDO phase.  We still haven't beaten the summer minimum of 2012, and we could be in a period of enhanced global warming, and reduced Arctic ice loss (at minimum)

edit:  It also occurs to me that we may be in a new circulation pattern, but this pattern is not quite an opposite of the previous dipole type pattern.  A nice natural cycle may immediately balance out a period of bad for ice pattern with a good for ice pattern.  But reality may switch from a bad to ice pattern to neutral, or even just less bad.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 20, 2017, 02:11:50 AM

Of course CO2 is impacting Pacific SSTs. 

Yes, but is not just CO2. There are industrial Aerosols like the ones jai mitchell keeps pointing at, there is deforestation that change the cloud patterns and temperatures, there is the accumulated warming in the Oceans ect.

Quote
But we also know there are significant natural variations at work over multi-decadal time frames in the tropical Pacific, namely PDO.

Yes, but the PDO is affected by human influence. I prefer "significant random variations" to  "significant natural variations". To me the word "Natural" has the connotation that the variation is beyond human influence. I find that extremely unlikely. I think "natural" is an improper term.

Quote
Looking at a trend in SSTs from 1979 to 2016 in GISS (https://data.giss.nasa.gov/gistemp/maps/) shows a significant cool PDO/ENSO signal over the time period in question.  Is Co2 causing a trend towards cooler PDO/ENSO?  If so the pause may not be totally a natural variation, but rather a negative feedback on global warming.  Or is this cooling due to a  natural variation?


I've noted in the past that the fastest loss in Arctic ice loss corresponds roughly to the period of pause in global temp increase.  Could easily be coincidence, but research linking both the pause and now the Arctic ice to tropical Pacific temps suggests something more. 


The first two images are crappy screenshots of the PDO according to NOAA and global Temperatures according to GISStemp from about 1979 to today.

Please notice that from around 1979 the PDO was mostly positive and global temperatures rose steadily until around the 90's. In the early 90's the PDO took  a dive and so did global temperatures. Then around 1998 the PDO switched to mostly negative and global temperatures stopped rising. Then after 2012 the PDO switched back to positive and the global temps followed.

The third image is Arctic sea ice extent. During this whole time Arctic sea ice was on decline. During the times of warming and during the times of cooling ice is being lost.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 20, 2017, 02:15:28 AM
In response to a number of posts discussing the issue of communication with a general audience and whether scientists in general or the authors here should be criticized for their language/format/style; here is an example of the climate denialist reaction; “Natural Variability’s Role in Arctic Sea Ice Decline Strengthens Case for Lukewarming”.

https://www.cato.org/blog/natural-variabilitys-role-arctic-sea-ice-decline-strengthens-case-lukewarming (https://www.cato.org/blog/natural-variabilitys-role-arctic-sea-ice-decline-strengthens-case-lukewarming)

In perusing this argument the concept of sophistry immediately comes to mind.

The logical incongruity in the last few paragraphs stands out. Cato’s fallacy begins with “But if a sizeable proportion of the ice loss is being caused by natural variability (and not greenhouse gas emissions), then some proportion of the warming observed over the past 30 years must be caused by the same forces of natural variability”… their contrived argument spins illogically out of control from there.

Cato incorrectly asserts, “This means that when comparing the rates of observed warming with the rates of warming expected by climate models, that natural variability acting on Arctic sea ice has been making the models seem to be closer to reality than they actually are.”

Huh! ???  The premise of the paper is that models do not explain the observed Arctic melt, so some other factor must be involved. Thus, they modified the model.

Cato goes illogically downhill from there, asserting the complete opposite of the finding of the study which is that the observed melt of Arctic Sea Ice can indeed be explained by geophysics. And that human activity has been a major driver.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 20, 2017, 02:43:19 AM
Regarding the semantic definition of ‘Natural Variations’ the recent discussion in climate science about changes in the variability of Northern Hemisphere Jet Stream comes to mind. Given that the Jet Stream naturally varies, if the frequency, magnitude and intensity of such variations are observed to change in a concerted way over time, in correlation with key factors driven by human activity, is such a variation still ‘natural’?  Similarly, if Arctic Sea Ice melt is observed to correlate with increased heat in the climate system resulting from human activity and also changes in atmospheric circulation (kind of sounds like changes in the jet stream…) How does one determine that an observed change in a complex process is natural and not driven by other factors known to be altering the system?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 20, 2017, 02:49:58 AM
This link allowed me to view the article but not save the PDF...

http://www.nature.com/articles/nclimate3241.epdf?referrer_access_token=HeIuODhYskeUEDXNGCR8kNRgN0jAjWel9jnR3ZoTv0MWnSoz10AxEp9R-_524q_J9CVW2xFH8GLB4wdMbyVvyVe9ReY6IyRWum3BWY6OQ1AP96sC_XNfgpe4RmCFW_SqdsB14hBgmHLAr5kAR_9oWqfZWVyQoHnB9RVMmvbr3jIq3-LQD5hV8hbfzw_cKiDmqVa13BzXJJEBBQWDnI633fk2pT7qquB3k0hK00u-o_8%3D&tracking_referrer=www.popsci.com (http://www.nature.com/articles/nclimate3241.epdf?referrer_access_token=HeIuODhYskeUEDXNGCR8kNRgN0jAjWel9jnR3ZoTv0MWnSoz10AxEp9R-_524q_J9CVW2xFH8GLB4wdMbyVvyVe9ReY6IyRWum3BWY6OQ1AP96sC_XNfgpe4RmCFW_SqdsB14hBgmHLAr5kAR_9oWqfZWVyQoHnB9RVMmvbr3jIq3-LQD5hV8hbfzw_cKiDmqVa13BzXJJEBBQWDnI633fk2pT7qquB3k0hK00u-o_8%3D&tracking_referrer=www.popsci.com)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: tzupancic on March 20, 2017, 03:18:25 AM
Just fyi, I once posted at some length on an obscure Solar Cycle 24 discussion forum about the Arctic Sea Ice that was dominated by climate change denialists. I learned a thing or two. If it matters, I am a Ph.D. scientist.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 20, 2017, 04:37:40 AM
The third image is Arctic sea ice extent. During this whole time Arctic sea ice was on decline. During the times of warming and during the times of cooling ice is being lost.

See Tamino's Analysis (https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/) from October 2015.  Here he shows evidence of faster ice loss during the last decade, and a slow down in recent years.  While he does not actually say the difference is statistically significant, from what I've seen of Tamino he would not put the break points in that chart if they weren't.

(https://tamino.files.wordpress.com/2015/10/annual_trend.jpeg?w=500&h=332)

Also see a more recent post (https://tamino.wordpress.com/2016/10/22/sea-ice-update-2/) with a Lowess smooth.  The recent years are definitely downward instead of close to level.  A  period of faster reduction is still visible, but as this is Lowess smooth and Tamino makes no specific comment there is no particular support for a change in speed, but the data is closer to up to date.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 20, 2017, 04:44:07 AM
The way I look at it the sun is the primary driver of the Earth's climate.Greater than 99.9% of the sun's influence is constant in Human time frames. The .1% of that energy that is not constant is the only "Natural" (free of human influence) variation left.

 .1% is such a small variation that for many (most?, all?) applications the total energy received from the sun can be used as a constant, but it is not constant it varies. Even if that variation is small, the sun probably varied about the same way for hundreds of millions of years. That means that all potential forces on the planet are influenced by the same  force. The big synchronization is with gravity, the topography of the planet, the day and night cycle. Over time I imagine that synchronization occurs between the photosynthetic biosphere and its dependencies.

I believe that variations like the PDO can be eventually tracked to solar variation but with lag determined by the many multi scale processes.

The PDO is indeed a natural variation. The thing is that with human induced warming the synchronicity is altered. For something like the PDO Natural is that when the PDO is positive, the global temperatures go up. When it is negative the global temperatures go down. However, we changed that. Under CO2 induced warming when the PDO is positive the temperature rises fast and when it is negative the temperature merely stops rising. The inevitable result is global warming.

Atmospheric currents are no different. They evolved under the same influences for millions of years. Now that we made the planet more energetic they must change. The change might be have been too small to notice for years, or perhaps the patterns were too complex to discern changes with accuracy, but the most basic physics dictate that the atmospheric currents must change with changes in temperature.



Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 20, 2017, 08:36:01 AM
In response to a number of posts discussing the issue of communication with a general audience and whether scientists in general or the authors here should be criticized for their language/format/style; here is an example of the climate denialist reaction; “Natural Variability’s Role in Arctic Sea Ice Decline Strengthens Case for Lukewarming”

Thanks for the heads up. However in response to your posts discussing climate denialist communications perhaps I might take this opportunity to criticize your style? Please do not give the likes of Messrs Michaels and Knappenburger the oxygen of publicity by linking to their hogwash. Instead link to archived versions like this one:

http://archive.is/wbTfu (http://archive.is/wbTfu)

Here is a list of such archived climate denialist reactions:

http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#AltDenialist (http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#AltDenialist)

Here once again is a further helpful hint:

http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#comment-219940 (http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#comment-219940)

I take it you are aware that the lunatics are now in charge of the asylum?

http://GreatWhiteCon.info/2017/03/that-deaf-dumb-and-blind-kid-sure-plays-a-mean-climateball/#comment-220045 (http://GreatWhiteCon.info/2017/03/that-deaf-dumb-and-blind-kid-sure-plays-a-mean-climateball/#comment-220045)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 20, 2017, 12:03:15 PM
Archimid,

You do not need a variable sun to create a PDO or any other natural oscullation. Just the shape and evolution of Earth' s orbit with local local Ocean and land topography is enough.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: crandles on March 20, 2017, 12:56:08 PM
Quote
Eric steig
2017/03/20
Jim hunt: your question being whether we “saw this coming”?
I certainly did. I written or been involved with that a number of papers that more or less say’ “hang on folks, not every bump and wiggle is forced change; much of it is intrinsic variability (or at least, more work is needed to demonstrate otherwise.” The response is always as expected from the no-nothings, which is some combination of quoting us as showing that natural variability dominates (no, we didn’t), and claiming that the scientific mainstream has previously ignored natural variability. I’m more surprised when I get criticism from my colleagues who’ve usually not yet read the paper carefully, though I’m beginning to get used to that. Should we have done something different? I don’t know what. Not published the paper, lest we inadvertently help the “skeptics”? Put in more disclaimers (I thought we had, actually)?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 20, 2017, 02:36:00 PM
Archimid,

You do not need a variable sun to create a PDO or any other natural oscullation. Just the shape and evolution of Earth' s orbit with local local Ocean and land topography is enough.

Yes of course. The PDO oscillation exists because of the topography of the planet and it would probably oscillate even if the sun was truly constant. From my perspective, if the sun was constant then the PDO would be more predictable that it is now. However the variation of the sun, even as small as it is, have reinforced and weakened oscillations like the PDO at regular intervals for millions of years. Over time that small reinforcing and weakening eventually influences the variability to the point where the variations are highly coupled with solar cycles after lag from multi scale processes is accounted for.

 A simple correlation of the PDO and solar cycles might not easily show this because of the many multi scale process involved and the shortness of the record. But if we had a record of the PDO for the last, I don't know, 10000 years and an equally good record of solar variation for the same time period I think a strong correlation would be found between solar variation and PDO cycles.

In that imaginary 10k year data set it could be observed that correlation weakens as it advances through the 20th century and human induced warming breaks the coupling that took millions of years to form.

TL;DR: The PDO is a natural variation whose magnitude and interaction with the rest of the system changed because of human induced warming.





Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 20, 2017, 03:38:23 PM
Eric steig
2017/03/20
Jim hunt: your question being whether we “saw this coming”?

In case it's not obvious, Crandles' quote was extracted from The Stoat. One of my follow up questions for Eric over there:

Quote
Any thoughts on this recent comment of mine at Neven’s Arctic Sea Ice Blog?

http://neven1.typepad.com/blog/2017/03/lowest-maximum-on-record-again.html?cid=6a0133f03a1e37970b01b8d26c9d01970c#comment-6a0133f03a1e37970b01b8d26c9d01970c (http://neven1.typepad.com/blog/2017/03/lowest-maximum-on-record-again.html?cid=6a0133f03a1e37970b01b8d26c9d01970c#comment-6a0133f03a1e37970b01b8d26c9d01970c)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 20, 2017, 05:38:53 PM
First, thank you Neven for practically immediately releasing my profile and welcoming me into the ASIF community. Also, thank you Archimid for starting this thread, and thank you Andre, Jim Hunt, jai mitchell, Jim Williams and oren, for your replies/comments.

Jim Williams, you ask: “OK...What is dangerous about it, and why should he [Ding et al] not make a dangerous argument?”

The argument that the demise of Arctic sea ice is in large part due to “natural climate variability” is dangerous because it feeds the rhetoric of the “merchants of doubt”, that climate change - as much as they accept that there is anything at all like climate change going on – is a “natural” phenomenon, etc. The ultimate conclusion of any such argument being that we don’t need to slow down or stop mining/extracting fossil carbon, and burning such fossil carbon and emitting GHG’s. In other words, let's keep the fossil carbon industry going.

Or, as jai mitchell put it in much better words than mine:
Quote
“… there are factions within the scientific community that work within the normal frameworks to provide contrarian views to reduce the mitigation imperative.”

Kevin Anderson and Glen Peters think along similar lines when they discuss the reliance of various emissions scenarios on negative emissions, the technology for which, as of March 2017, simply doesn’t exist. (see http://www.geoengineeringmonitor.org/2016/10/the-trouble-with-negative-emissions/ (http://www.geoengineeringmonitor.org/2016/10/the-trouble-with-negative-emissions/)) Negative emissions are a neat doublethink-like trick to justify the convenient concept of a “carbon budget”, in other words, how much extra carbon we can still burn if we want to keep global warming under 2C.

Michael E. Mann has previously calculated that if we wanted to keep global warming under 2C, we would have to keep CO2 concentration under 450ppm; that was allowing for a 0.5C overshoot for a few decades, AND the widespread use of negative emission technologies after 2050. Without the widespread use of negative emission technologies after 2050, we would have to keep CO2 concentration under 405ppm. (see https://www.scientificamerican.com/article/earth-will-cross-the-climate-danger-threshold-by-2036/ (https://www.scientificamerican.com/article/earth-will-cross-the-climate-danger-threshold-by-2036/))

We are already at 405ppm. In other words, without relying on negative emissions technologies that as of March 2017, do not exist, our “carbon budget” is zero. We have to stop emitting GHG’s right now (the “mitigation imperative” that jai mitchell mentions). Bad news for fossil fuel companies? No, not really. Even the Paris agreement doesn’t consider the possibility of immediately implementing zero net emissions worldwide.

And, one can expect the next IPCC report to fully rely on emissions scenarios that include increasingly massive negative emissions beginning at around 2050. Are IPCC climate scientists – or even Michael Mann – going around claiming that the 2C limit is unrealistic? No they aren’t.

Similarly, the complete disappearance of Arctic sea ice – not only during summer, but year round – is by now totally inevitable in the space of a few decades, as one of the charts I posted in my first comment shows. Unfortunately, the argument made by Ding et al in their paper will lead to the following cynical discourse, which will be duly relayed to the general public by mainstream media:

Quote
But hey, if it’s due to “natural climate variability”, it has nothing to do with the fossil carbon industry, right?

And to all those who claimed that Arctic sea ice was “the canary in the mine” of climate change here is the news for you: Science says it ain’t so. The canary may be dying or have died, but it was from natural causes.

So, while we waste time discussing whether or not the paper by Ding et al is scientifically correct, "Bad Science" or just crap, or should have been worded differently, Arctic sea ice will continue to silently melt away and the fossil carbon industry will keep digging/extracting millions of tons of fossil carbon, to be released as GHG’s into the atmosphere.

Eric Steig, one of the authors of the paper, asks (thank you Jim Hunt for posting the exchange): “[Should we] Not [have] published the paper, lest we inadvertently help the “skeptics”?” The answer, imho, is pretty obvious.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: crandles on March 20, 2017, 06:06:19 PM

Eric Steig, one of the authors of the paper, asks (thank you Jim Hunt for posting the exchange): “[Should we] Not [have] published the paper, lest we inadvertently help the “skeptics”?” The answer, imho, is pretty obvious.

IMHO the answer is pretty obvious that yes they should publish provided they put in appropriate caveats. If the answer was no then how do you expect science to advance? Also note the "quoting us as showing that natural variability dominates (no, we didn’t)". That seems pretty clear that the authors are not expecting a huge bounce back up by 60% of the drop. I would have preferred that to have been stated more clearly so as to reduce the chances of the paper being spun in the way it has been but however clearly done, do we really expect that to make much difference to how it is spun?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 20, 2017, 06:54:36 PM

Eric Steig, one of the authors of the paper, asks (thank you Jim Hunt for posting the exchange): “[Should we] Not [have] published the paper, lest we inadvertently help the “skeptics”?” The answer, imho, is pretty obvious.

IMHO the answer is pretty obvious that yes they should publish provided they put in appropriate caveats.
...

Hi crandles,
Actually the Ding paper is generously sprinkled with caveats. But that has never prevented the fossil fuel industry propaganda writers from running with whatever argument they could extract from any scientific or opinion paper that would feed their rhetoric. If you don't believe me, just check Jim Hunt's blog for how mainstream media is "reporting" on this Ding et al paper.

So, unfortunately, I don't agree with you. Responsible, intelligent adults don't feed the narrative that Arctic sea ice is melting because of "natural climate variability". This paper should not have been published. And I am not even commenting on its scientific value, which imho is below the temperature (in degrees Celsius) at which ice transitions from solid to liquid.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on March 20, 2017, 07:36:35 PM

Eric Steig, one of the authors of the paper, asks (thank you Jim Hunt for posting the exchange): “[Should we] Not [have] published the paper, lest we inadvertently help the “skeptics”?” The answer, imho, is pretty obvious.

IMHO the answer is pretty obvious that yes they should publish provided they put in appropriate caveats.
...

Hi crandles,
Actually the Ding paper is generously sprinkled with caveats. But that has never prevented the fossil fuel industry propaganda writers from running with whatever argument they could extract from any scientific or opinion paper that would feed their rhetoric. If you don't believe me, just check Jim Hunt's blog for how mainstream media is "reporting" on this Ding et al paper.

So, unfortunately, I don't agree with you. Responsible, intelligent adults don't feed the narrative that Arctic sea ice is melting because of "natural climate variability". This paper should not have been published. And I am not even commenting on its scientific value, which imho is below the temperature (in degrees Celsius) at which ice transitions from solid to liquid.
I think it was appropriate to publish  as long as it passed peer review.  It is dangerous to politicize research.

That said, I think it is behooves us and them to better delineate the source of that natural climate variability, as I expect climate change outside of the Arctic has affected it and shifted it's range of variation.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: crandles on March 20, 2017, 07:54:19 PM

So, unfortunately, I don't agree with you. Responsible, intelligent adults don't feed the narrative that Arctic sea ice is melting because of "natural climate variability". This paper should not have been published. And I am not even commenting on its scientific value, which imho is below the temperature (in degrees Celsius) at which ice transitions from solid to liquid.

To me this translates to I have a closed mind and will never accept that I am wrong on this issue whatever and however the science develops, I am going to keep the same opinion.

Even if it is wrong, the scientific way to find out is publish and be damned. (or not damned)

and yes re 'as long as it passed peer review'.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 20, 2017, 08:58:45 PM
...
Even if it is wrong, the scientific way to find out is publish and be damned. (or not damned)
...
Hi crandles,
Again, I am not even arguing about the scientific value of the Ding paper per se here, or how it was worded, or how many caveats it was filled with.

I am talking about giving the "merchants of doubt" an excellent basis for further delaying the urgent and radical emissions reductions policies that need to be put in place to avoid the worst consequences of global warming - including famines, wars, forced migration, etc, and the suffering and ultimately death that these will bring to hundreds of millions of human beings.

So, are you a moral human being first and (questionable) scientist second, or does your oversized ego take precedence? In the case of Ding and his ten(!) co-authors, it seems the latter.

"Science sans conscience n'est que ruine de l'âme." - Rabelais

Now, of course since they have already been published, they have legitimized the clearly false assertion that the year-round disappearance of Arctic sea ice which will occur over the coming few decades is mostly due to "natural climate variability". You could demonstrate that they are entirely wrong, de-construct all the fallacies in their tortuous reasoning, dissect their various logic mistakes, point to each and every dubious assumption they make in the paper, it wouldn't matter: they cannot be unpublished. And clearly, people with such an oversized ego are not going to retract themselves or even admit that they were wrong and wrote a piss-poor excuse of a climate science paper.
So there you have it.
Arctic sea ice is going to disappear over the coming years but now the takeaway from this man-made disaster is that it's mostly "natural climate variability". Crappy (un)science is the new normal.
Talk about improving communications between climate scientists and the general public!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: mikkel on March 20, 2017, 10:00:22 PM
Andrew, I completely agree with you about our dire straits. I continuously get frustrated that the scientific community is in a bit of denial about what their own work shows and that even many who aren't in denial haven't been public about it.

The only high profile examples of scientists who I know accurately communicate the "true" consensus are Michael Mann and James Hansen, with Jason Box chipping in on Greenland. Even then, only Hansen has proper emotional sense of urgency in his communication, although this often gets entirely lost when talking in specifics (which he acknowledges).

As I am apt to comment, the consensus is that 4-5C of warming is enough to threaten civilization itself, and the supposedly radical Paris targets are actually for 6C long term. Therefore our "goal" is civilization collapse!

That said, I feel you are being way too hard on these scientists. I completely understand why, as I went through the same phase of grief myself. It drove me to spend many years study propaganda and the nature of mass social movements, with the purpose of somehow teaching scientists how their actions are contributing to the problem.

Instead I came to discover the root of the problem lay in lack of solid leadership and compassion for how society operates. Those of us who genuinely see reality spend our time trying to communicate and get people to understand, because this is what personally moves us. However, it is not the principal driver for the vast majority of people, and in fact information overload causes them to dig in their heels.

By contrast, propagandists are skilled in leading the masses by tailoring communication in ways that are most effective for mass influence.

The fact is that data and models have almost no real contribution to denier propaganda. They literally make up shit even about the most straightforward and clear science, and if it is too hard to spin then it is just ignored. It seems to us that every single statement and paper must be perfect so that we cannot be taken advantage of (e.g. ClimateGates) but this is a trap: the obsession with accuracy and consistency only brings us further down the rabbit hole of disconnection. At its worst, it leads to internal conflict and ad hominems that break down cooperation.

I would strongly recommend you read "Don't Even Think About It" by George Marshall, who does an excellent job of showing how we all contribute to paralysis on social change, and how the propagandists (of which he interviews one) are only a very small part of the puzzle.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on March 20, 2017, 10:02:54 PM
...
Even if it is wrong, the scientific way to find out is publish and be damned. (or not damned)
...
Hi crandles,
Again, I am not even arguing about the scientific value of the Ding paper per se here, or how it was worded, or how many caveats it was filled with.

I am talking about giving the "merchants of doubt" an excellent basis for further delaying the urgent and radical emissions reductions policies that need to be put in place to avoid the worst consequences of global warming - including famines, wars, forced migration, etc, and the suffering and ultimately death that these will bring to hundreds of millions of human beings.

So, are you a moral human being first and (questionable) scientist second, or does your oversized ego take precedence? In the case of Ding and his nine(!) co-authors, it seems the latter.

"Science sans conscience n'est que ruine de l'âme." - Rabelais

Now, of course since they have already been published, they have legitimized the clearly false assertion that the year-round disappearance of Arctic sea ice which will occur over the coming few decades is mostly due to "natural climate variability". You could demonstrate that they are entirely wrong, de-construct all the fallacies in their tortuous reasoning, dissect their various logic mistakes, point to each and every dubious assumption they make in the paper, it wouldn't matter: they cannot be unpublished. And clearly, people with such an oversized ego are not going to retract themselves or even admit that they were wrong and wrote a piss-poor excuse of a climate science paper.
So there you have it.
Arctic sea ice is going to disappear over the coming years but now the takeaway from this man-made disaster is that it's mostly "natural climate variability". Crappy (un)science is the new normal.
Talk about improving communications between climate scientists and the general public!
Actually, I don't think they asserted most of the loss was from natural variation, and I suggest the philosophical discussion get moved to an appropriate thread.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 20, 2017, 10:34:03 PM
Actually, I don't think they asserted most of the loss was from natural variation, and I suggest the philosophical discussion get moved to an appropriate thread.
Hi jdallen,
From the abstract of the paper:
Quote
Our experiments indicate that the circulation trend may have contributed as much as 60% to
the decline of the September sea ice extent minimum since 1979.

Now, of course, the use of the word "experiments" is entirely wrong in the paper. Ding et al didn't perform any climate or Arctic sea ice experiment. They use the word "experiments" to describe their playing with two different models under 5 different sets of assumptions/data, hence the five "experiments" from which they derive their conclusion above.

Another problem with the abstract, and I am surprised that nobody has yet pointed it out here in this forum, is this idiotic statement:
Quote
A strengthening upper tropospheric anticyclonic anomaly over Greenland and the Arctic Ocean increased the downwelling longwave radiation above the ice by warming and moistening the lower Arctic troposphere.
So, none of the thousands of climate scientists who had previously worked - sometimes for decades - in the Arctic had ever guessed that warm, moist air was melting the sea ice. OK...

Do you really want to discuss the minutiae of how this climate science paper is total, utter crap, as Jim Williams intuited above? But then we are falling straight into the trap that this paper has setup for all the people who are concerned about reducing GHG emissions ASAP.

"Climate scientists can't even agree among themselves whether climate change (or how much of it) is the result of human activity."
"It's not settled science."
"CO2 is not the main driver of climate change."
"They were growing wheat in Greenland some centuries ago and nobody was any worse for it."
Etc.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 20, 2017, 11:33:07 PM
AndrewB, welcome and thank you for putting it so concisely. To me argument 1 is still the most important, and I find the scientific claim highly questionable. The negative arctic sea ice trend is so obvious that attributing it to variable natural causes unrelated to AGW and GHGs using a model, probably means the model is not good enough.
Hi oren,
Thank you for your comment. Indeed the Ding et al paper makes the following claim, found in the abstract:
Quote
"Our experiments indicate that the circulation trend may have contributed as much as 60% to the decline of the September sea ice extent minimum since 1979. Because the observed circulation variability over the Arctic is inconsistent with the expected model response to anthropogenic forcing, a significant component of sea ice loss over the last three decades may have been driven by dynamical sources of natural climate variability."
And in their conclusion:
Quote
"The forcing of the summer sea ice by the trends in large-scale circulation, which are likely due mostly to natural variability, represents an important driver of the observed Arctic climate change."
They used two different models to reach these conclusions:
1) ECHAM5, an atmospheric general circulation model developed at the Max Planck Institute for Meteorology (see http://www.mpimet.mpg.de/en/science/models/echam/ (http://www.mpimet.mpg.de/en/science/models/echam/)). Actually ECHAM5 is not intended for modeling Arctic sea ice, and has been superseded by ECHAM6. Why Ding et al chose to use an obsolete version of an atmospheric general circulation model beats me - unless they wanted a model that would best fit their foregone conclusions. The source code for ECHAM6 is freely available for lawful scientific use, and you can basically run the model on a properly configured desktop Linux workstation.
Now, even more puzzling is that the Max Planck Institute for Meteorology actually has a model specifically developed for modeling Arctic sea ice, see here (http://www.mpimet.mpg.de/en/science/the-ocean-in-the-earth-system/scientific-working-groups/sea-ice-in-the-earth-system/#c10229 (http://www.mpimet.mpg.de/en/science/the-ocean-in-the-earth-system/scientific-working-groups/sea-ice-in-the-earth-system/#c10229)) and here (http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016-discussion.html (http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016-discussion.html))
2) A global coupled ocean/sea-ice (POP2-CICE4) model, developed at UCAR (Ding). See http://www.cesm.ucar.edu/models/ (http://www.cesm.ucar.edu/models/) for details. Obviously Ding is most familiar with POP2-CICE4.

The paper is lacking in that they don't quantify the skill of the models they used, they just claim they are "better" (actually they don't even use the word "skill", which is the proper technical term). I would suggest they used the models that "better" worked out to show their claim that sea ice decline is mostly the result of "natural climate variability". A clear example of manipulating your "experiment" to reach a desired conclusion.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 21, 2017, 03:14:52 AM

See Tamino's Analysis (https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/) from October 2015. -snip-

To the proposed slowdown of the trend I say that extent is not a good measure for how much ice has been lost. I shouldn't used the monthly extent myself. Volume is a better measure of ice loss. Attached maximum and minimum Arctic Sea ice volume according to PIOMAS. I don't see a slowdown. I'm looking forward to Tamino's next look into the matter.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Ninebelowzero on March 21, 2017, 06:18:20 PM
I don't see a slowdown. I'm looking forward to Tamino's next look into the matter.


The blue plot has the appearance of rough "cobbles" for most of it's plot. There's probably a good reason for that.

The red plot is more erratic and the biggest yearly drop is about 3500 cubic km but there's no section there to compare with the plot of the last 4 years.

How indicative is the dotted average line of what will actually happen in the next few years?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: magnamentis on March 21, 2017, 06:19:47 PM

See Tamino's Analysis (https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/) from October 2015. -snip-

To the proposed slowdown of the trend I say that extent is not a good measure for how much ice has been lost. I shouldn't used the monthly extent myself. Volume is a better measure of ice loss. Attached maximum and minimum Arctic Sea ice volume according to PIOMAS. I don't see a slowdown. I'm looking forward to Tamino's next look into the matter.

seconding that while the stats should be in percent in addition to just numbers because once we shall reach volumes below the current range between min and max the numbers will have to slow down while the percentage will accelerate. I hope that i was able to explain the thought in a comprehensive manner while perhaps someone else, a native english speaker, can/will do that better.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Pragma on March 21, 2017, 07:24:08 PM
If I am reading the original graph correctly, it is not indicating a slowdown at all.

This is easy to misinterpret because it shows the anomaly on a yearly basis, which is still increasing.

So, while there appears to have been a sharper year-on-year increase previously, we are still at the maximum per year change.

Even if the graph were to completely flatten out, we would still be dropping per year at the maximum observed rate of ~ 750 k km^2

That said, I agree with others that extent is not the best way to evaluate things, due to wind and currents, as well as the theoretical possibility that we could have just a thin veneer of ice, and the extent would still stay the same.

Volume is the true measure. Unfortunately, there still seems to be a disturbing discrepancy between the various products.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 22, 2017, 06:45:56 AM

To the proposed slowdown of the trend I say that extent is not a good measure for how much ice has been lost. I shouldn't used the monthly extent myself. Volume is a better measure of ice loss. Attached maximum and minimum Arctic Sea ice volume according to PIOMAS. I don't see a slowdown. I'm looking forward to Tamino's next look into the matter.

Looks to mirror the overall pattern for extent loss.  A faster period after 2000, and then a slower period in the last 5 or so years.  By itself I would hesitate to call anything other than random variation around a trend.  But it seems close enough to Tamino's extent analysis suggesting a non-trivial slow down to suggest the same applies to volume.  Also there were a few people extrapolating the short term trend up to about 2012 in volume to a 0 volume in 2016, and the recent years have clearly and significantly diverged from this extrapolation.  I remember taking these extrapolations quite seriously, and being puzzled by the fact that an extrapolation of extent suggested ice free in several decades and extrapolation of volume in several years.  Some people at that time seemed convinced by the idea that volume was more important than extent and so ice free in several years was the likely outcome.  They now look likely to be wrong, although a really big drop in Arctic ice to near 0 in the next few years would redeem this point of view and suggest that the old up was just a luck weather variation.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: TheUAoB on March 22, 2017, 02:46:07 PM
Surely the metric that really counts is total sea-ice mass.  Volume doesn't describe the quality/density of the ice any more than extent or area shows thickness.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: josh-j on March 22, 2017, 02:48:08 PM
If I am reading the original graph correctly, it is not indicating a slowdown at all.

This is easy to misinterpret because it shows the anomaly on a yearly basis, which is still increasing.

So, while there appears to have been a sharper year-on-year increase previously, we are still at the maximum per year change.

Even if the graph were to completely flatten out, we would still be dropping per year at the maximum observed rate of ~ 750 k km^2

If you're referring to Tamino's graph, I think it is showing the cumulative anomaly, not the rate of change. So an anomaly of -1 would mean 1 less than normal. not a rate of change of -1 per unit of time.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 22, 2017, 03:46:43 PM
Surely the metric that really counts is total sea-ice mass.  Volume doesn't describe the quality/density of the ice any more than extent or area shows thickness.

I see Area/extent as a "compression" of volume. The compression allows for simpler understanding of some phenomena highly related to area at the cost of the information lost during the compression.

Volume and mass combine to give us density. Density is probably a very good indicator of actual ice conditions, however spatial information that volume provides is lost.

How useful knowing the Mass alone would be? I guess it will give the capacity of the ice to overcome waves, export and other physical interactions, but spatial information would be lost.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on March 22, 2017, 08:50:41 PM
Surely the metric that really counts is total sea-ice mass.  Volume doesn't describe the quality/density of the ice any more than extent or area shows thickness.

I see Area/extent as a "compression" of volume. The compression allows for simpler understanding of some phenomena highly related to area at the cost of the information lost during the compression.

Volume and mass combine to give us density. Density is probably a very good indicator of actual ice conditions, however spatial information that volume provides is lost.

How useful knowing the Mass alone would be? I guess it will give the capacity of the ice to overcome waves, export and other physical interactions, but spatial information would be lost.

Actually, the metric being looked for is total energy required to melt -- and no, I do not know how to obtain that.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: sidd on March 22, 2017, 10:39:45 PM
Re: energy to melt arctic ice

The Arctic floating icecap annually melts and refreezes aprroximately 20,000 Gigatons. If the ice were land based, this would correspond to a sea level rise and fall of 60 mm annually. The amount of heat involved  is close to the net  yearly radiative imbalance. Net Radiative imbalance from 1972-2008 due to greenhouse gases is  5.6e21 J/yr or about 183 Terawatt for the whole earth(Church,2011,  doi:10.1029/2011GL048794).

sidd
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on March 22, 2017, 11:18:20 PM
Re: energy to melt arctic ice

The Arctic floating icecap annually melts and refreezes aprroximately 20,000 Gigatons. If the ice were land based, this would correspond to a sea level rise and fall of 60 mm annually. The amount of heat involved  is close to the net  yearly radiative imbalance. Net Radiative imbalance from 1972-2008 due to greenhouse gases is  5.6e21 J/yr or about 183 Terawatt for the whole earth(Church,2011,  doi:10.1029/2011GL048794).

sidd
Probably need to move this off into Stupid Questions or some such, but TheUAoB's original question "Surely the metric that really counts is total sea-ice mass.  Volume doesn't describe the quality/density of the ice any more than extent or area shows thickness" and your interesting reply has peaked my interest...so.

Do you think you can convert your cost to melt what is in fact melted into a cost to melt it all (either in Joules or Terawatts)?  It might also be interesting to do that as percentages of current mass and current excess heat.  Sort of a ball-park, how close are we really to a Blue Ocean Event?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 23, 2017, 10:29:05 AM
Back on-topic to the discussion of the Ding et al paper, I would like to point to an excellent rebuke of the Ding paper on a scientific basis, written by Rob Dekker in a long comment on the Stoat blog, which you all can find here:
http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58495 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58495)
Here is Rob's conclusion, with which I agree 100%:
Quote
That would have been a fine conclusion, but is completely different from their conclusion that “summertime atmospheric circulation” may have contributed as much as 60% to the September sea-ice extent decline since 1979.
It’s not “summertime atmospheric circulation” that caused it; it is “summertime climate change (with ALL the variables, including temperature) being the cause. And with AGW being real, we know that temperature for one is NOT a natural variability variable.

So Ding et al 2017 made the ASSUMPTION that the temperature TREND in the Arctic is part of natural variability and they base their conclusions on that.

Needless to say that that assumption (in a warming world) is quite preposterous, and I wonder what the authors were thinking when they drew their conclusions.
(emphasis mine)

(btw, I just noticed that Rob Dekker is also a registered ASIF member, I hope he can (re-)post his rebuke in this thread)

And Rob, since you asked this question "I wonder what the authors were thinking when they drew their conclusions(?)", my answer is that they already had the preposterous claim that the disappearance of sea ice is up to 50% due to natural variability in mind, and just found the models and performed the simulations (which they call "experiments") that would somehow support their a priori conclusion.

Also, if I may add, it is a well-known fact here at ASIF, that the weather (natural variability) during the months of June-July-August is a determining factor in how low September ice extent will go. But that in no way is the correct attribution for the year-round exponential decrease TREND in Arctic sea ice volume, which we can observe since the beginning of satellite records, as evidenced by this excellent chart:
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 23, 2017, 05:30:09 PM
And Rob, since you asked this question "I wonder what the authors were thinking when they drew their conclusions(?)", my answer is that they already had the preposterous claim that the disappearance of sea ice is mostly due to natural variability in mind, and just found the models and performed the simulations (which they call "experiments") that would somehow justify their a priori conclusion.

AndrewB - did you bother to read Eric Steig's comment at Stoat's?  What is with this constant character assassination of climate scientists in these threads lately?  I feel like I'm at WUWT.

So, we have a peer-reviewed paper by a plethora of well-respected and leading climate scientists that challenge your beliefs.  OTOH we have a few paragraphs by a non-scientist on a blog.  Occam's razor would lead you to believe the non-scientist's blog post is correct.  Good grief, Charlie Brown.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on March 23, 2017, 06:05:33 PM
And Rob, since you asked this question "I wonder what the authors were thinking when they drew their conclusions(?)", my answer is that they already had the preposterous claim that the disappearance of sea ice is mostly due to natural variability in mind, and just found the models and performed the simulations (which they call "experiments") that would somehow justify their a priori conclusion.

AndrewB - did you bother to read Eric Steig's comment at Stoat's?  What is with this constant character assassination of climate scientists in these threads lately?  I feel like I'm at WUWT.

So, we have a peer-reviewed paper by a plethora of well-respected and leading climate scientists that challenge your beliefs.  OTOH we have a few paragraphs by a non-scientist on a blog.  Occam's razor would lead you to believe the non-scientist's blog post is correct.  Good grief, Charlie Brown.
Careful how you apply that razor - it may be cutting things you want to keep. You've used an ad hominem argument against an ad hominem statement.

Criticism from non-professionals is still relevant when well founded.  The correct take on this should be, how well supported is the critique, and does it raise reasonable questions?

Pertinent to the first statement - a conclusion against paradigm does not necessarily establish any fact regarding the person (s) making it.  Who wrote a paper is fairly irrelevant.  What is relevant is its content.

That is what should be under discussion, not personalities.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 23, 2017, 06:55:30 PM
Yep. I agree with jdallen. Who wrote it or on what medium does not matter. The only thing that matter is the content. Most of the content of the paper in question is scientifically valid but there are large claims whose validity was not demonstrated but assumed.

Extraordinary claims require extraordinary evidence. Claiming that atmospheric variation is natural is an extraordinary claim. Common sense dictates that there are both natural and anthropogenic elements to atmospheric variation. Good science would quantify how much of the atmospheric variation is anthropogenic and how much is natural.Then they can make correct attributions.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 23, 2017, 07:34:30 PM

Looks to mirror the overall pattern for extent loss.  A faster period after 2000, and then a slower period in the last 5 or so years. 

I think there is more to it that meets the ice. The first image is that of maximum volume and minimum volume. I would call to your attention that for 2017 the record max volume is very likely to be quite a bit lower than the record minimum. If that comes true that reinforces the downward trend.


I would agree with you that after 2007 something changed.

I took Max Volume - Min Volume as the volume lost in a year and Min Volume - Max Volume of the following year as the volume gained in a year. Those are the 2nd and 3rd charts.

I  think the most interesting of those graphs is the volume gain, which shows a side effect of the phenomenon you and Tamino are pointing at. After 2007 the arctic started creating much more ice every year than before.

Here are the stats for the whole data set, for 1980-2006 and for 2007-2016

AvgVolGain       16.59010811
MedianVolGain      16.455
MaxVolGain      19.659
MinVolGain      14.709
Variance      1.373940821
      
AvgVolGain 1980-2006      16.13581481
MedianVolGain  1980-2006      16.3
MaxVolGain  1980-2006      17.62
MinVolGain  1980-2006      14.709
Variance 1980-2006      0.519474464
      
AvgVolGain  2007-2016      17.8167
MedianVolGain 2007-2016      17.864
MaxVolGain 2007-2016      19.659
MinVolGain 2007-2016      14.872
Variance 2007-2016      1.704214678


Both the average and median after 2007 are higher than the max before 2007 with twice as much variance. Something certainly changed. The Arctic is making much more ice than before because there is a lot less old ice. That making of ice is what Tamino, the slow transition and others are pointing at as the savior of the ice.

But here is the thing. The more ice the arctic makes each year the higher temperatures become. The more ice the arctic makes the more fdd's go into making ice instead of showing up as a colder atmosphere. The inevitable result of higher temperatures is that less ice is made. Heat keeps being added to the system due to CO2, lower albedo for longer and changes in the atmospheric current that bring even more water into the system. This is likely to get worse before it gets better.


Which brings me back to Ding et al. Did they rule out whether causation goes the other way? Changes in the ice causes changes in the atmospheric circulations?




Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Steven on March 23, 2017, 07:47:41 PM
my answer is that they already had the preposterous claim that the disappearance of sea ice is mostly due to natural variability in mind, and just found the models and performed the simulations (which they call "experiments") that would somehow justify their a priori conclusion.

You are misrepresenting the Ding et al. paper.  They never claimed that the disappearance of sea ice is mostly due to natural variability.  Quote from the abstract:

Quote
Internal variability dominates the Arctic summer circulation trend and may be
responsible for about 30–50% of the overall decline in September sea ice since 1979.

http://www.atmos.washington.edu/~david/Ding_etal_inpress_2017.pdf (http://www.atmos.washington.edu/~david/Ding_etal_inpress_2017.pdf)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Steven on March 23, 2017, 07:54:35 PM
Claiming that atmospheric variation is natural is an extraordinary claim. Common sense dictates that there are both natural and anthropogenic elements to atmospheric variation. Good science would quantify how much of the atmospheric variation is anthropogenic and how much is natural.Then they can make correct attributions.

Again, this is addressed in the paper.  Ding et al. estimate that:

(1) about 60% of the September Arctic sea-ice extent decline since 1979 is caused by trends in summertime atmospheric circulation. 
(2) about 70% of those atmospheric circulation trends is caused by internal variability (and hence the remaining 30% is anthropogenic). 

Combining those two estimates, they get:

Quote
we estimate that about
~42% (70% × 60%) of the sea-ice decline observed since 1979 in
September is due to internal variability.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 23, 2017, 07:57:29 PM
So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 23, 2017, 08:17:39 PM
So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss?

(https://confessionsofasomedaysomebody.files.wordpress.com/2015/10/4bj3.gif)
guess we will just have to . . .wait. . .and. . .see. . . . .. . . . . . . . . .. . .. . .  .. .. . .
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 23, 2017, 08:27:15 PM
...
You are misrepresenting the Ding et al. paper.  They never claimed that the disappearance of sea ice is mostly due to natural variability.
...

From the abstract, in both the submitted and published versions:

Quote
Our experiments indicate that the circulation trend may have contributed as much as 60% to the decline of the September sea ice extent minimum since 1979.

From the conclusion in the final submitted version:

Quote
The forcing of the summer sea ice by the trends in large-scale circulation, which are likely due mostly to natural variability, represents an important driver of the observed Arctic climate change.
(emphasis on the word 'mostly' mine)

That last phrase was completely removed in the published version of the paper.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: magnamentis on March 23, 2017, 08:36:52 PM
at times it's trouble some to discuss things that seem obvious just because there are people how try to stand out by opposing anything that is based on common sense and try to land a lucky punch that way with a chance to boost their carrier. it wouldn't matter so much if it would not cost us time and energy that would be essential to be used to find solutions, workarounds and damage minimization instead of fighting the trolls.

that said, why did i say that:

a) the speed of warming without obvious natural cause leaves little to no room to believe it's natural  (at least not mainly)

b) the correlation between the development of our climate to the warmer side with the level of civilization, industrialization and wealth ( use of energy consuming technology and comfort tools) leaves no to little room
to assume that the warming at the current speed and exactly during the given period is naturally caused, again at least not mainly,

i' know it's bold and somehow not correct to say so but i think there always is a point where certain discussions and/or doubts should simply be banned due to be provenly wrong.

this what we are facing here is obviously mainly man-made and any energy that goes into convincing the always yesterday people should be gathered for productive thoughs and action instead.

[rant end LOL]
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 23, 2017, 11:12:11 PM

Again, this is addressed in the paper.  Ding et al. estimate that:

(1) about 60% of the September Arctic sea-ice extent decline since 1979 is caused by trends in summertime atmospheric circulation. 
(2) about 70% of those atmospheric circulation trends is caused by internal variability (and hence the remaining 30% is anthropogenic). 

Combining those two estimates, they get:

Quote
we estimate that about
~42% (70% × 60%) of the sea-ice decline observed since 1979 in
September is due to internal variability.

I don't contend anything in the paper except the attribution to "natural variability" vs anthropogenic. I think my problem is on Page 10 line 222 of this version:http://www.atmos.washington.edu/~david/Ding_etal_inpress_2017.pdf (http://www.atmos.washington.edu/~david/Ding_etal_inpress_2017.pdf)

Quote
Second, to estimate the anthropogenic contribution to the observed warming and sea ice reduction in the Arctic, two additional experiments are conducted. Exp-7 and 8 are equivalent to the Exp-2 but we remove the effects of global warming on the high latitude winds, which are used to constrain the model in Exp-2 .

I would love to see how they define the "effects of global warming". Is it just CO2 and Methane or  are albedo changes, glacier changes, sea temperature changes or any secondary effect of CO2 induced warming included? What about non GHG human forcings like deforestation, industrial gases, heat island effects, air travel, do they account for those?

 I tried to dig deeper but this is what I find on  EXP-7

Quote
Same as Exp-2, except that ECHAM5 is nudged to a modified observed wind patterns in which the long term trends of simulated winds (zonal and meridional winds) in the ensemble mean (26 members) of CMIP5 during 1979 to 2014 are removed from observation.

So they removed the trends and what remains is the natural variability?

Let's dig deeper, what is experiment 2?

>Same as Exp1, except that a simple slab ocean/sea ice model is used in the Arctic, north
445 of 60ºN.

A simple slab?  I understand the computational limitations, and I further understand that insight can be gained even with gross simplifications.  But if you are going to attribute changes of sea ice I hope that slab is not as simple as it sounds simple.

So on to Exp1

Quote
Because we are interested in the impact of the long-term trend of the observed circulation in our model simulations, and to facilitate our computation efforts, we interpolate observed monthly ERA-I data to daily fields for nudging. We use a very weak damping term to nudge the 3-D (from surface to the top of atmosphere) divergence and vorticity fields of the model to the observed monthly (smoothly interpolated to daily) fields in the last 36 years; this weak damping allows the model to generate its own day-to-day variability but constrains the model to be very close to the observed circulation on monthly and longer time scales. In the lower boundary, we impose climatological SST/sea ice everywhere. Anthropogenic forcings are held constant in this experiment.


I wonder what forcings they include as anthropogenic forcings. I also wonder what they mean by holding them constant.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 24, 2017, 12:39:32 AM
So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss?

Five years ago.

Or maybe not.  We'll see.....
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Adam Ash on March 24, 2017, 03:29:52 AM
So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss?

Well, with 'business as usual' (or just a minor methane burp) we could see global mean wet bulb temperatures cross human body core temperatures for a few days a year.  That will tidy up most warm blooded animals, including the chief operators of anthropogenic CO2 emitting systems.

Then, with no further non-natural emissions, we (sorry, 'Gaia', we will be gone) then Gaia is left to break down methane and draw down CO2 by natural processes, until CO2 'flips back again' to pre-Anthropocene levels. 

So - when?  In a few million years.  And of our 'civilisation'?  A thin stain in a strata of rocks and a peculiar level of background radiation as 50,000 tonnes of reactor fuel plumed into the atmosphere from 500 out of control nuke power plants whose deceased operators had stopped twiddling the knobs.

(Sorry, OT, but you did ask!)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: epiphyte on March 24, 2017, 04:23:55 AM
So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss?

Well, with 'business as usual' (or just a minor methane burp) we could see global mean wet bulb temperatures cross human body core temperatures for a few days a year.  That will tidy up most warm blooded animals, including the chief operators of anthropogenic CO2 emitting systems.

Then, with no further non-natural emissions, we (sorry, 'Gaia', we will be gone) then Gaia is left to break down methane and draw down CO2 by natural processes, until CO2 'flips back again' to pre-Anthropocene levels. 

So - when?  In a few million years.  And of our 'civilisation'?  A thin stain in a strata of rocks and a peculiar level of background radiation as 50,000 tonnes of reactor fuel plumed into the atmosphere from 500 out of control nuke power plants whose deceased operators had stopped twiddling the knobs.

(Sorry, OT, but you did ask!)

Can't remember who wrote it, but when I was a kid I read a science fiction story about a time traveler who came to a sticky end when he went back to find out what happened to the dinosaurs. only to discover that the velociraptors all had guns, and were gearing up for a nuclear war.

I wonder if they would have been skeptical about the possibility of Sauriogenic global cooling (!)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on March 24, 2017, 05:36:19 AM
Andrew, thank you for guiding me to this thread in ASIF about Ding et al 2017.

I looked in detail at the science of the paper, and discovered that it does not sustain the conclusions. Not at all. There simply is no evidence in the (methods and experiments of the) paper that ANY "internal variability" played ANY role in "the overall decline in September sea ice since 1979" as the paper asserts in the abstract.

I have attempted to explain the problems in the paper on several posts on William Connolley's "stoat" site, with the most detailed technical analysis here :
http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58495 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58495)

Now that comment was pretty technical, so I've posted a new comment that tries to explain the problem in simpler terms :

Quote
From the abstract we read “trends in summertime atmospheric circulation may have contributed as much as 60% to the September sea-ice extent decline since 1979”.

However, that is NOT what the paper’s methods show.

For starters, in the methods (model experiments) “atmospheric circulation” variable is represented by “geopotential height” over the Arctic summer, specifically Z200 (geopotential height at 200 mb). So the correct conclusion would be “trends in summertime geopotential height may have contributed as much as 60% to the September sea-ice extent decline since 1979”.

With that conclusion, you can feel the correlation-versus-causation issue coming up : Arctic temperature increase (due to AGW) may be the cause of or geopotential height increase.
And consequently you can no longer claim that the (up) trend in both variables is a source of “internal variability”.

And thus the final conclusion (that “Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30–50% of the overall decline in September sea ice since 1979”) no longer holds.

I'd invite anyone here to challenge my findings, but please use the paper's technical information as arguments. If I'm correct, then the paper is scientifically deceiving, and the way in which this deception is done is not unlike what I've seen in papers from Richard Lindzen and Willie Soon.
But since this paper has names like Alex Schweiger and Eric Steig (both of whom I greatly respect) on it, I wonder how much these guys were involved. I hope not much.

In summary : Ding et al 2017 does NOT provide ANY evidence of ANY influence of "internal variability" on Arctic sea ice decline since 1979.

So we are still stuck with the ONE long term cause for Arctic sea ice decline : AGW.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 06:47:15 AM
Thank you Rob for your brilliant dissection of the Ding et al paper. We are still waiting for any of the authors to manifest themselves and respond to your sharp criticism or any of the other questions raised by their scientifically questionable and evidence-defying "natural climate variability" attribution for Arctic sea ice decline, here on ASIF or on the Stoat blog comments section.

Meanwhile, 2017 just saw the lowest maximum Arctic sea ice extent on record, 2016 was the third hottest year on record in a row and 1.1C above pre-industrial, and atmospheric CO2 concentration has passed the 405ppm threshold, 125ppm above pre-industrial and probably the highest it has been in over 1 million years. And 25% of the world's corals died last year.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 24, 2017, 07:00:51 AM
So they removed the trends and what remains is the natural variability?

Let's dig deeper, what is experiment 2?

>Same as Exp1, except that a simple slab ocean/sea ice model is used in the Arctic, north
445 of 60ºN.

A simple slab?  I understand the computational limitations, and I further understand that insight can be gained even with gross simplifications.  But if you are going to attribute changes of sea ice I hope that slab is not as simple as it sounds simple.

The above criticism is nonsense. 

Quote
The general circulation model used to perform the experiments (Exps-1 to 4,7 and 8 ) in this study is the ECHAM5 atmospheric general circulation model,with a horizontal resolution of T42 (∼2.8◦latitude ×2.8◦longitude) and 19 vertical levels. In Exps-2, 3, 7 and 8, we coupled the ECHAM5 to a slab ocean in the high latitudes to assess the role of prescribed circulation in driving the SST and sea ice in the Arctic.

They are using an *atmospheric circulation model* to assess atmospheric circulation and only tying it to an ocean module when they want to see the near surface effects on SSTs (top 50 meters). If you believe this is insufficient, then perhaps you should cite from the peer-reviewed literature *why* it is insufficient.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 07:23:32 AM
...
They are using an *atmospheric circulation model* to assess atmospheric circulation and only tying it to an ocean module when they want to see the near surface effects on SSTs (top 50 meters).
...
Of course they are using an (obsoleted version of an) atmospheric circulation model (ECHAM5). Because they want to show that the decline in Arctic sea ice in September is mostly due to atmospheric circulation variability in the Arctic in June-July-August, which they then attribute to "natural climate variability".

In other words, Ding et al are using the specific model that best supports the conclusion they want to reach.

Why don't they use the specific Arctic sea ice model from the Max Planck Institute for Meteorology? Why don't they quantify the skill of the models they use, and compare them to other models for Arctic sea ice? https://en.wikipedia.org/wiki/Forecast_skill

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 24, 2017, 12:38:48 PM


The above criticism is nonsense. 



It may be. This paper is way above me as I do not know the intricacies of the models used, but is so contrarian to everything else I know that I must do what I can to either confirm it or deny it for my own peace of mind. So far the small part I understand from the paper tell me that the "natural variation" claim is BS. Other more knowledgeable members have provided good arguments to confirm that.

Quote
They are using an *atmospheric circulation model* to assess atmospheric circulation and only tying it to an ocean module when they want to see the near surface effects on SSTs (top 50 meters). If you believe this is insufficient, then perhaps you should cite from the peer-reviewed literature *why* it is insufficient.

I'm sure a simplification of the ocean/atmosphere interaction is sufficient for many applications. But in a paper examining cause and effect of arctic sea ice and a paper that attempts to quantify the attribution of the changes in sea ice using such a simplification is very suspicious.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 24, 2017, 02:38:11 PM

Of course they are using an (obsoleted version of an) atmospheric circulation model (ECHAM5). Because they want to show that the decline in Arctic sea ice in September is mostly due to atmospheric circulation variability in the Arctic in June-July-August, which they then attribute to "natural climate variability".

In other words, Ding et al are using the specific model that best supports the conclusion they want to reach.


Basically slander.  This belongs on the pages of WUWT. 

Zero evidence for,"... they *want* to show...."
Zero evidence for, "using the specific model that best supports the conclusion they want to reach..."

It's really become sad that this forum has degenerated into nothing but an analogue to WUWT comments - just with a different perspective.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 24, 2017, 02:53:51 PM
The whole forum? Or just one (or a couple) out of 1200+ members?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 02:54:11 PM
...
Zero evidence for,"... they *want* to show...."
Zero evidence for, "using the specific model that best supports the conclusion they want to reach..."
...

From the Ding et al paper:

Quote
In this paper we examine the contribution of the atmospheric circulation to Arctic sea ice variability by utilizing an atmospheric general circulation model (ECHAM5) in which the circulation field is nudged to observations.

And further down:

Quote
How sea ice variability and trends can impact the Arctic atmospheric circulation is an area of vigorous research. Studies suggest numerous mechanisms in which sea ice loss modulates the large-scale circulation in the lower troposphere in winter. This paper, instead, focuses on how the high-latitude circulation impacts sea ice.
(emphasis mine)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: FredBear on March 24, 2017, 03:00:47 PM
Please remember:--

Occam's razor
KISS (Keep It Simple, Stupid!)

Ding et al 2017 have blinded me with science (I am not competent to judge their methods) and just leave me trying to decide whether there is truth in their summary.
By Occam's razor, earlier forcasts that predicted climate change as a result of increased CO2 (especially in polar regions) appear to coming true, so extra complicated models with all manner of caveats just serve to confuse (or encourage cherry-picking?) and are not necessary.
As people see it, it will come down to "60% natural variability (+40% human influence?)" versus "human influence" - there is a common factor if it is mentioned!
KISS!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 24, 2017, 03:04:32 PM
The whole forum? Or just one (or a couple) out of 1200+ members?

Unfortunately, I'd say a growing number.  And what we also witness is the herd mentality where those who make such asinine statements are not called out by others.  I.e., I don't like the paper results either so I won't bother to chastise him for being an idiot about it - or some such logic.

The first rule of Dunning-Kruger is if you think an expert is wrong, you probably don't understand something.  Do we want to count the dozens - possibly hundreds - of climate papers the authors of Ding et al have been part of?

Have we forgotten Tietsche et al already?  Just because you don't like a result doesn't mean it's incorrect.   The paper may be fatally flawed, but if it is it will be much more subtle than anything dreamed up here.  The idea that simple errors were missed by the authors or the peer-reviewers is rather hard to swallow given the conclusion. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on March 24, 2017, 03:22:04 PM
Please remember:--

Occam's razor
KISS (Keep It Simple, Stupid!)

Ding et al 2017 have blinded me with science (I am not competent to judge their methods) and just leave me trying to decide whether there is truth in their summary.
By Occam's razor, earlier forcasts that predicted climate change as a result of increased CO2 (especially in polar regions) appear to coming true, so extra complicated models with all manner of caveats just serve to confuse (or encourage cherry-picking?) and are not necessary.
As people see it, it will come down to "60% natural variability (+40% human influence?)" versus "human influence" - there is a common factor if it is mentioned!
KISS!
Actually, I think that is more in keeping with the definition of a prophet (one who only makes predictions which turn out to come to pass), but I have to agree that we ought to pay more attention to those who warned us that CO2 would cause the the air to warm than to those who stir the pot and say it wasn't so much the CO2.

Occam's razor, though stated in several forms, is more along the lines of: don't suggest more entities (causes) than you need to to explain the data.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 24, 2017, 03:25:52 PM
...
Zero evidence for,"... they *want* to show...."
Zero evidence for, "using the specific model that best supports the conclusion they want to reach..."
...

From the Ding et al paper:

Quote
In this paper we examine the contribution of the atmospheric circulation to Arctic sea ice variability by utilizing an atmospheric general circulation model (ECHAM5) in which the circulation field is nudged to observations.

And further down:

Quote
How sea ice variability and trends can impact the Arctic atmospheric circulation is an area of vigorous research. Studies suggest numerous mechanisms in which sea ice loss modulates the large-scale circulation in the lower troposphere in winter. This paper, instead, focuses on how the high-latitude circulation impacts sea ice.
(emphasis mine)

And here is the word *WANT* AndrewB ???  You said they wanted to reach a certain conclusion.  That's scientific fraud.  You said they chose the model that would give them the result they *WANTED*. 

Go tell these scientists they rigged the results to get the conclusion they wanted.

Qinghua Ding
Axel Schweiger.
Stephen Po-Chedley.
Eric Steig.
Michelle L'Heureux.
David Battisti.
Nathaniel C. Johnson.
Eduardo Blanchard Wrigglesworth.
Qin Zhang.
Kirstin Harnos.
Ryan Eastman.

Do you even recognize these names?  Do you know just who it is you're accusing?  You're a nut.  The analog to the typical commenter at WUWT.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 03:41:49 PM
...
Go tell these scientists they rigged the results to get the conclusion they wanted.
...

I never wrote "they rigged the results to get the conclusion they wanted." I wrote, and confirm that I meant exactly that, Ding et al chose the models to support the conclusion that they wanted to arrive at.

You are suggesting that they didn't, in other words you are suggesting that they randomly chose some climate models, ran their simulations, and then were collectively surprised to find out that "atmospheric circulation" in the months of June-July-August shows a high correlation with Arctic sea ice extent in September, in their simulation runs.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 24, 2017, 03:43:38 PM

Of course they are using an (obsoleted version of an) atmospheric circulation model (ECHAM5). Because they want to show that the decline in Arctic sea ice in September is mostly due to atmospheric circulation variability in the Arctic in June-July-August, which they then attribute to "natural climate variability".

In other words, Ding et al are using the specific model that best supports the conclusion they want to reach.


Basically slander.  This belongs on the pages of WUWT. 

Zero evidence for,"... they *want* to show...."
Zero evidence for, "using the specific model that best supports the conclusion they want to reach..."

It's really become sad that this forum has degenerated into nothing but an analogue to WUWT comments - just with a different perspective.


Funny how I see something entirely different. I see several people taking a stab at the science and trying to get to the bottom of this extraordinary claim.

For example Rob Dekker's claim:

Quote
For starters, in the methods (model experiments) “atmospheric circulation” variable is represented by “geopotential height” over the Arctic summer, specifically Z200 (geopotential height at 200 mb). So the correct conclusion would be “trends in summertime geopotential height may have contributed as much as 60% to the September sea-ice extent decline since 1979”.

I can certainly agree that conclusion. I think is a good scientific conclusion with dire implications. However that's where science ends.  The authors take the attribution a step further without providing any evidence . They conflate  the trends of geopotential heights and winds to "natural variability".

May I recommend that instead of engaging in ad hominems and appeals to authority yourself you explain how values for pressure and wind used in this experiment are free of anthropogenic influence? Maybe answering Neven's question, "when is this cycle turning around?" would yield better results.


Forget about the authors. Let's talk about the content.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 24, 2017, 03:55:14 PM
I never wrote "they rigged the results to get the conclusion they wanted." I wrote, and confirm that I meant exactly that, Ding et al chose the models to support the conclusion that they wanted to arrive at.

How is that substantively different than rigging the results?  And you reinforce my point about a conclusion they *wanted* -- but you have zero evidence for either claim, both of which are essentially academic malfeasance or scientific fraud.

Don't worry, Archimid will pat you on the back.

You *don't* know who these authors are, do you?  LOL.

Axel Schweiger - PIOMAS
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 24, 2017, 04:00:44 PM
Okay, enough now. ktonine has a point that we should try not to imply malfeasance or ignorance on the part of scientists. At the same time this paper was spinned by the people who wrote the press release or whatever, and this was then spinned further by those who have nothing to offer but spin. So, it's understandable that people are upset by this.

Either way, back to content. Or just let this fizzle out, as it doesn't mean all that much in the big picture. But let's not fight over this.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 24, 2017, 04:09:05 PM

Don't worry, Archimid will pat you on the back.


**Archimid pats AndrewB's back**

Let's do it buddy, truth is on our side.

Quote
You *don't* know who these authors are, do you?  LOL.

No, and I don't care. I only care about the truth in their science. Do you realize that your argument is appeal to authority? That might work with Trump or the WUWT community, but it doesn't work for me. I only care about the message, not the messenger or the medium for the message.

Let's get back to science shall we? Help me get rid of my ignorance. How and why trends in geopotential heights equal "natural variability"?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 24, 2017, 04:26:13 PM
Okay, enough now. ktonine has a point that we should try not to imply malfeasance or ignorance on the part of scientists.

I agree with malfeasance. However, isn't the purpose of science to eradicate ignorance? It is ok to not know. Science is the mechanism to cure not knowing.

Quote
At the same time this paper was spinned by the people who wrote the press release or whatever, and this was then spinned further by those who have nothing to offer but spin. So, it's understandable that people are upset by this.

I couldn't agree more. I think this was blown out a proportions by a malicious use of "natural variation" implying that the reduction of the sea ice is mostly not anthropogenic. Do a search in the document for "natural variation". Is not even there. The 60% attribution to natural variation  was the spin the media gave it.


But the document does use language loosely and can very easily be interpreted as what the media portrays.


This will be my last post on this topic, unless meaningful discussion resumes.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 24, 2017, 04:31:51 PM
I only care about the truth in their science. Do you realize that your argument is appeal to authority? That might work with Trump or the WUWT community, but it doesn't work for me. I only care about the message, not the messenger or the medium for the message.

Let's get back to science shall we? Help me get rid of my ignorance. How and why trends in geopotential heights equal "natural variability"?

Dunning - Kruger.  If you believe that an expert opinion in a field is the same as a random blog comment, then you are insane.

From Ding et al,

Quote
Regressing the domain-averaged sea-ice anomaly time series against the JJA geopotential height at 200 hPa (Z200) in ERA-I, we find that decreasing sea ice is accompanied by increasing Z200, withmaximum amplitude over Greenland (Supplementary Fig. 1).

These same interrelationships between the trends in the indices of JJA Z200, temperature, water vapour, DLR and September sea-ice concentration are also apparent using detrended indices: an Arctic summer with higher than normal Z200 over Greenland,greater DLR at the surface, and increased low-level water vapour and temperature over the Arctic is followed by negative sea-ice anomalies in September (Fig. 1c); for example, detrended indices of temperature and specific humidity are correlated atr = 0.89; detrended indices of sea-ice concentration and DLR are correlated at r = −0.75. Importantly, the detrended data shows that the summertime anomalies in the indices of near-surface temperature, DLR, and water vapour are simultaneously associated with a common pattern of atmospheric circulation variability (seeFig. 1d–g), and that this circulation pattern is very similar to the circulation pattern that is associated with the sea-ice interannual variability in September (see Fig. 1d–g). These correlation maps also compare well with the p an-Arctic Z200 and surface wind trends inJJA (Fig. 1b), which feature a strong high over northeastern Canada,Greenland, and t he Arctic Ocean.

I suggest you read the paper.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Pettit on March 24, 2017, 04:38:33 PM
Dunning - Kruger.  If you believe that an expert opinion in a field is the same as a random blog comment, then you are insane.

...

I suggest you read the paper.

A reminder from way back about half-an-hour ago:

Okay, enough now. ktonine has a point that we should try not to imply malfeasance or ignorance on the part of scientists. At the same time this paper was spinned by the people who wrote the press release or whatever, and this was then spinned further by those who have nothing to offer but spin. So, it's understandable that people are upset by this.

Either way, back to content. Or just let this fizzle out, as it doesn't mean all that much in the big picture. But let's not fight over this.

Thanks!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 04:41:34 PM
...
Either way, back to content. Or just let this fizzle out, as it doesn't mean all that much in the big picture. But let's not fight over this.

Neven, I am not quite sure what to make of what you just wrote here, so please help me out here.
;)
(I hope a little bit of humor is allowed in this thread, to lighten up the atmospheric circulation mood)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 04:47:23 PM

**Archimid pats AndrewB's back**


**AndrewB thanks Archimid and pats Archimid's back back**

 :)

...
Do a search in the document for "natural variation". Is not even there. The 60% attribution to natural variation  was the spin the media gave it.
...

Ding et al don't use the expression "natural variation". They use, abundantly and at different times, either "natural variability", "natural climate variability" or "internal variability" to signify non-anthropogenic forcing.

The 30~50% attribution is found in the abstract:
Quote
"Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30-50% of the overall decline in September sea ice since 1979."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 24, 2017, 05:09:00 PM
Sorry Neven, I feel like I must answer this, including the ad hominem.


Dunning - Kruger.  If you believe that an expert opinion in a field is the same as a random blog comment, then you are insane.

If you believe that experts are always correct you are also insane. As I said, I judge what I read by the content not by the messenger or medium. I value expert opinion very highly, but not blindly. I also value peer reviewed publications over all other forms of publications.

From Ding et al,

Quote
Importantly, the detrended data shows that the summertime anomalies in the indices of near-surface temperature, DLR, and water vapour are simultaneously associated with a common pattern of atmospheric circulation variability (seeFig. 1d–g), and that this circulation pattern is very similar to the circulation pattern that is associated with the sea-ice interannual variability in September (see Fig. 1d–g).


I do not contend that is false. It makes sense to me and I think it is very bad news. What I contend is that the  atmospheric circulation variability is not necesarilly "natural variability".  It is natural variability only in that it varied randomly since 1979.

Neven, this time I'm done for real.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Yuha on March 24, 2017, 05:10:51 PM
I've looked Ding et al. in some detail and in the end came to the conclusion that there is nothing really new or surprising in their experimental results. They simply verify what was already known or suspected.

The issue with their conclusions about natural variation is not with the experiments but with the more fundamental premise that the CMIP5/LENS model ensemble mean represents the actual AGW effect cleaned of natural variation and that any deviation from the model mean is natural variation. If that is the premise, there is nothing surprising in the conclusions.

I know that many consider that premise obviously wrong but it is not quite that simple. Individual model runs do exhibit large deviations from the mean sometimes lasting several years, so it isn't out of the question that what we are seeing in the real world is something similar. On the other hand, declaring an observed deviation from the model mean automatically as natural variation rather than a potential model error seems to me equally unfounded. But then I'm not an expert so what do I know.

So the question really is, are models right or wrong (or perhaps something in between), and I don't think this paper provides much help in answering that.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 24, 2017, 05:18:32 PM
I've looked Ding et al. in some detail and in the end came to the conclusion that there is nothing really new or surprising in their experimental results. They simply verify what was already known or suspected.

I quite agree.  A couple years ago here on the forum Chris Reynolds and I came to much the same conclusion regarding summer vs winter.  Might be in the Slow Transitions topic.  Essentially we were able to convince ourselves that the data supported that both winter and summer were contributing to the decline, but that extra warm summers had a very large effect.

2007 is often referred to as the perfect melt season - well, that's natural variability. 
PIOMAS reached it's all-time low in 2012 and hasn't returned to that level since.  That's natural variability.

The trend is all going in one direction and that's due to AGW, but simply writing off natural variability is ignoring science, the data, and the facts.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 05:28:44 PM
...
So the question really is, are models right or wrong (or perhaps something in between), and I don't think this paper provides much help in answering that.

"Essentially, all models are wrong, but some are useful" - George Box

The Ding paper unfortunately does not explain in details how the decision to use the models they used came about, nor does it quantify the skill of the models they used, or compare their skill to other models, including sea ice specific models that they fail to mention and did not use.

Models are widely used and a most important tool for research in climate science. Just because the Ding et al paper raises so many questions about the models they used and the conclusion they apparently derived from them, does not in any way invalidate the use of models in climate research.

Two videos with Gavin Schmidt about the use of models in climate science:
https://www.youtube.com/watch?v=JrJJxn-gCdo (https://www.youtube.com/watch?v=JrJJxn-gCdo) (TED talk)
https://www.youtube.com/watch?v=WfwgaMHmLkU (https://www.youtube.com/watch?v=WfwgaMHmLkU) (1 hour lecture, with very bad sound unfortunately)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 24, 2017, 06:07:19 PM

If the arctic climate were in perfect balance then all of the melt in any given year would be replaced by an equal amount of freeze.  We would have a seasonal cycle that wouldn't necessarily be a sine wave, but it would be repeated year after year with equal amplitude minimums and maximums.

The fact that there is overall loss does NOT mean the process is driven by more melt - only that melt exceeds freeze. As I tried to explain, there are 3 possibilities mathematically (assuming the process is thermodynamic and the loss is not due to chaotic variability and the time window open to us just happens to be when the random chaotic features lead to a loss).

If we accept that the loss is a trend, and we know there are only 3 possible explanations, examination of the data tells us which of these possibilities is actually in effect - both melt and freeze are increasing, but melt is on average larger than freeze. But even knowing this does not tell us whether the losses are due to winter or summer processes.

We know that global warming does not just manifest itself in a particular month or season, but that does not mean that it's uniform.  Chris is actually asking (I think), Is the Arctic thermal balance more anomalous in winter or summer?  Arctic sea ice extent, area and volume anomalies are just indicators of this energy imbalance. 

The intuitive answer is that the losses are driven by summer melt processes.  The data seems to bear intuition out: The correlations between the preceding winter and summer melt are very low.  The correlations between melt and the following freeze are significant (though barely at 95% and with a small sample size).

BUT .... arctic winter warming is 4 times larger than summer warming! Hmmm .... back to the drawing board.

A consistent story has to mesh with all the facts.  The fact that winter warming is greater than summer warming in the Arctic is not, on its face, consistent with an explanation that says summer processes are responsible for the ice losses.

In looking for a freeze-melt correlation - and finding none - I believed the preceding winter's volume gain told us little about the summer melt losses.  This may be misleading.  Just because it's true doesn't actually prove anything.  What if volume gain isn't a particularly significant attribute of winter?

In fact, after a couple days reflection I believe that is actually the case - that volume gain per PIOMAS tells us very little about winter.  Arctic temperatures historically on average fall to -45 C°.  That's far lower than necessary to create ice.  There is also a thermodynamic limit to how thick sea ice can grow over the winter. So a 5 C° warming during winter may not lead to any less ice, but it will lead to more summer losses - since less energy is needed to raise the ice temperature to the melting point.

Take a look at the Interpolated surface OLR for February 2013  (http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/comp.pl?var=NOAA+Interpolated+OLR&level=300mb&mon1=1&mon2=1&iy=2013&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&iy=&ipos%5B1%5D=&ipos%5B2%5D=&ineg%5B1%5D=&ineg%5B2%5D=&timefile0=&tstype=0&timefile1=&value=&typeval=1&compval=1&lag=0&labelc=Color&labels=Shaded&type=1&scale=100&labelcon=1&switch=1&cint=5&lowr=140&highr=200&proj=Custom&xlat1=066&xlat2=90&xlon1=0&xlon2=360&custproj=Northern+Hemisphere+Polar+Stereographic&level1=1000mb&level2=10mb&Submit=Create+Plot)and compare it to previous Februarys.  One has to go back to at least 2004 to find anything similar.  Probably 2002 or earlier.  It's also pretty easy to show that the February OLR plots are very closely related to the summer losses.  Rank them in order just by visual appearance and you'll come out very close to the same order as the actual losses.

In summary, the fact that PIOMAS volume gains for the preceding winter do not correlate to summer losses is probably misleading.  We used this lack of correlation to prove to ourselves that winter didn't determine summer losses - but the lack of correlation only tells us that volume gain is not correlated to summer losses, not winter in general. 

The winter OLR plots, particularly January and February, tell a different story.  The OLR plots should be a rough proxy for ice temperature.  And there's a huge energy difference between melting ice that might be at -40 C° as opposed to ice that might be 'only' -30 C°.

Of course I reserve the right to change my mind - again :)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Yuha on March 24, 2017, 06:48:02 PM
Models are widely used and a most important tool for research in climate science. Just because the Ding et al paper raises so many questions about the models they used and the conclusion they apparently derived from them, does not in any way invalidate the use of models in climate research.

I fully agree. Models are really our only chance of separating trend from natural variation in recent events. We do not have multiple earths or an ability to rerun history or to see in the future. And models are remarkably skillful and getting better all the time. I'm eagerly waiting results from the next generation of models.

However, arctic is probably the most difficult place on earth to model because of ice and snow, the large temperature differences and the complex geography.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jplotinus on March 24, 2017, 07:18:05 PM
<snip, it really has been enough now; N.>
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 07:53:24 PM
...
However, arctic is probably the most difficult place on earth to model because of ice and snow, the large temperature differences and the complex geography.
I agree. The Arctic is particularly difficult to model, as you say because of ice, snow, the ocean, the temperature range, the geography, the huge scale and numerous feedbacks and how all these interact. It's a complex system with a lot of chaos.
You might be interested in checking this paper:
The CMIP6 Sea-Ice Model Intercomparison Project (SIMIP): understanding sea ice through climate-model simulations
by Dirk Notz, Alexandra Jahn, Marika Holland, Elizabeth Hunke, François Massonnet, Julienne Stroeve, Bruno Tremblay and Martin Vancoppenolle

Somehow, the Ding et al paper "forgot" to even mention it...
http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016.pdf (http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016.pdf)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Steven on March 24, 2017, 08:28:20 PM
Somehow, the Ding et al paper "forgot" to even mention it...
http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016.pdf (http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016.pdf)

Your criticism is absurd.  That Notz et al. paper was still undergoing peer review when Ding et al. was submitted.

Notz et al. paper in its final revised form was published on 23 September 2016. 

Ding et al. paper was submitted on 26 July 2016.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 08:40:44 PM
Somehow, the Ding et al paper "forgot" to even mention it...
http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016.pdf (http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016.pdf)

Your criticism is absurd.
...
Ding et al. paper was submitted on 26 July 2016.

Steven, the Notz paper was submitted on 29 March 2016, four months before the Ding et al paper was submitted. With 11 co-authors, you would expect at least one among Ding et al. would have been aware of the Notz et al paper about the Sea-Ice Model Intercomparison Project (SIMIP), or at least about the SIMIP project itself, which exists since late 2015/early 2016 as far as I can tell. The climate model community is not that large.
Also, check where Notz works and where Ding et al got the ECHAM5 model from.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 24, 2017, 08:46:51 PM
How do you mention a paper that hasn't even been published yet?

AndrewB, you've made your point. Now don't reiterate it constantly by nitpicking details. Thanks.

And don't tell people to go and do this or that.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 24, 2017, 08:53:21 PM
How do you mention a paper that hasn't even been published yet?
APA REFERENCE STYLE: Unpublished Sources
http://linguistics.byu.edu/faculty/henrichsen/APA/APA14.html (http://linguistics.byu.edu/faculty/henrichsen/APA/APA14.html)
Quote from: Neven
AndrewB, you've made your point. Now don't reiterate it constantly by nitpicking details. Thanks.
You are welcome, Neven. Keep up the good work.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on March 25, 2017, 08:04:08 AM
Back to content.
I realized that my previous post I was not clear enough about the science to be convincing.
So let me try again, this time pointing out exactly what is wrong with the conclusions of Ding et al 2017.

First of all, what does Ding et al claim.
I think it was Steven who correctly pointed out that there are TWO parts to Ding et al's claims of influence of "internal variability" on Arctic sea ice :

Quote
(1) about 60% of the September Arctic sea-ice extent decline since 1979 is caused by trends in summertime atmospheric circulation. 
(2) about 70% of those atmospheric circulation trends is caused by internal variability (and hence the remaining 30% is anthropogenic). 

Now the problem I have with the paper are very clearly in point (1) :
It started with Ding et al claim in the abstract of that point :

Quote
Here, we present evidence that trends in summertime atmospheric circulation may have contributed as much as 60% to the September sea-ice extent decline since 1979.

In my previous post, I noted that Ding et al uses "GL-Z200" (geopotential height at 200 mb, over Greenland) as their metric for "atmospheric circulation" over the Arctic.
That immediately means that the conclusion should have read something like this :

Quote
Here, we present evidence that trends in summertime geopotential height may have contributed as much as 60% to the September sea-ice extent decline since 1979.

Now, this should raise some eyebrows here and there, since geopotential height is clearly directly correlated with temperature. If the temperature goes up, so does geopotential height.
In fact, the ideal gas law (PV=nRT) DICTATES that geopotential height goes up with temperature.
Which is sustained in the ERA data set, where Ding et al itself reports that there is a R=0.94 correlation between geopotential height and temperature.

So AGW, which is certainly a part (if not all) of the trend in temperature over the Arctic is certainly also a part (if not all) of the trend in geopotential height.
And thus Ding et al 2017 can no longer claim that the Z200 trend (which they call "atmospheric circulation trend") is a source of "internal variability".

But that's not all.
The even bigger problem with the paper is in which they determined the influence of "atmospheric circulation" (oops, I mean geopotential height) on Arctic sea ice decline.

If you want to investigate that influence with a sea ice/climate model, you would run the model with the ERA climate parameters, and compare it with a run that has geopotential height adjusted (subtract the geopotential height anomalies from the ERA data).

But that is not what Ding et al did.
They adjusted ALL variables (geopotential height, temperature, moisture content, downwelling LW radiation etc), essentially making the 'climate' constant.
Specifically, this is described here in the paper :

Quote
Exp-6: Same as Exp-5 except that the atmospheric forcing is modified to excise the forcing associated with the trends in the Greenland circulation pattern. To remove the circulations trend from the observat ions, we first construct the thirty-six-year seasonal (JJA) averaged time series of the Z200 index over Greenland, Z200 GL (GL-Z200 in Fig. 1c). We then linearly regress a key variable B
against this time series to obtain spatial pattern β(x,y) of the variable associated with the Greenland circulation index. Specifically, for the variable B we have

B(x, y, t) = β(x, y) × Z200 GL (t) (1)

where B represents a forcing field (for example, 10 m zonal wind, DLR, temperature, and so on), x and y indicate the location, t indicates time (JJA), Z200 GL is the Greenland Z200 index (GL-Z200 in Fig. 1c), and β is the regression coefficient. In the second step, the seasonal mean anomalous value of each forcing field is subtracted from the observed daily (or 6-hourly) forcing data during the summer—rendering a modified forcing that does not include variability or trends in variables that are asso ciated with Z200 GL. In the nine non-summer months, the forcing is exactly the same as that used in the Exp-5 control experiment. Given a strong correlation between circulation and surface winds, temperature, specific humidity, sea-level pressure, and downwelling long wave radiation in the Arctic, variability and trends in these six variables that are associated with Z200 GL are processed and removed from the forcing. The initial states of ocean, sea ice and atmosphere in Exp-5 and Exp-6 are exactly the same.

I highlighted in bold the section that describes that indeed they adjusted ALL variables to the extent that they linearly associate with Z200 GL. And because the correlation between all these variables and Z200 is very high (see figure 1c in the paper), they effectively eliminated ALL trends in ALL variables from their Exp-6 run, which means they effectively made the climate constant in that run.
Since the climate did not change in that run, they obtained a much lower ice melt rate.
Essentially the conclusion should thus have been :

Quote
Here, we present evidence that trends in summertime climate change may have contributed as much as 60% to the September sea-ice extent decline since 1979.

Which means that (this experiment 5 versus 6 suggests that) :
60% of Arctic sea ice reduction is caused by summer-time climate change, while 40% is caused by climate change over the remaining 9 months.

Which is an interesting conclusion, but as you can see it has NOTHING to do with ANY sort of "natural variability", so Ding et al cannot use it in their variability conclusion either.

You can still choose not to believe that this paper is seriously flawed, but you can no longer claim that you did not know.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 25, 2017, 08:47:01 AM
Back to content.

Yes, thank you Rob.

Quote from: Rob Dekker
...
Which means that (this experiment 5 versus 6 suggests that) :
60% of [September] Arctic sea ice [extent] reduction is caused by summer-time [(the immediately preceding three months, i.e. June-July-August)] climate change, while 40% [of September Arctic sea ice extent reduction] is caused by climate change over the remaining [previous] 9 months.
...

Just to be crystal clear here, I have taken the liberty of adding the details (in bold) that you had omitted for concision.

In other words, their conclusion should have been that September Arctic sea ice extent decline is 60% (i.o.w., mostly) determined by climate change over the three previous June-July-August months and 40% determined by climate change over the previous September-October-...-May months.

Or in even simpler terms, within the context of AGW, the model simulations they used show that the months immediately prior to September have more weight in determining how low Arctic sea ice will go, than other months further in the past.

Which is totally logical, but nothing new and nothing noteworthy.

And had this been their conclusion in the published version of their paper, you and I and the rest of the world probably wouldn't even have taken notice of it. Well, I for one wouldn't, for sure.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 25, 2017, 11:47:10 AM
Conclusions:
* expertise is earned. Because your name goes on a journal paper you are not automatically expert
* experts have blind spots and biases and make mistakes too
* because you just write in a forum of mostly amateurs you are not automatically an ignoramus
* if you want to criticise experts have your ducks in a row  ( thanks Rob)
* chill...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 25, 2017, 11:58:39 AM
At the risk of drifting off topic, may I take this opportunity to point out that whilst we debate how many angels can dance on the head of a pin the cryodenialospheric porky pie production line is cranking up to full speed once again?

Lamar Smith’s Show Trial for Climate Models (http://afwetware.org/2017/03/23/lamar-smiths-show-trial-for-climate-models/)

Quote
All in all there’s several “alternative facts” in just the headline and opening paragraph of the GWPF’s press release, which doesn’t augur well for the contents of the report itself.

We feel sure that Lamar Smith and the House Committee on Science, Space and Technology will nonetheless be pleased to see this report become public shortly before their planned hearing on March 29th entitled “Climate Science: Assumptions, Policy Implications, and the Scientific Method“:

We also feel sure they were pleased to view the contents of another recent “white paper” published under the GWPF banner. The author was ex Professor Judith Curry, and the title was “Climate Models for the Layman“
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 25, 2017, 12:22:25 PM
At the risk of drifting off topic, may I take this opportunity to point out that whilst we debate how many angels can dance on the head of a pin the cryodenialospheric porky pie production line is cranking up to full speed once again?

Lamar Smith’s Show Trial for Climate Models (http://afwetware.org/2017/03/23/lamar-smiths-show-trial-for-climate-models/)

Quote
All in all there’s several “alternative facts” in just the headline and opening paragraph of the GWPF’s press release, which doesn’t augur well for the contents of the report itself.

We feel sure that Lamar Smith and the House Committee on Science, Space and Technology will nonetheless be pleased to see this report become public shortly before their planned hearing on March 29th entitled “Climate Science: Assumptions, Policy Implications, and the Scientific Method“:

We also feel sure they were pleased to view the contents of another recent “white paper” published under the GWPF banner. The author was ex Professor Judith Curry, and the title was “Climate Models for the Layman“

It would be an excellent topic if he had real experts instead of three bozos and an expert....
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 25, 2017, 01:08:30 PM
At the risk of drifting off topic, may I take this opportunity to point out that whilst we debate how many angels can dance on the head of a pin...
And I always thought that here on ASIF we were debating how many angels can dance on the remaining Arctic sea ice in September?  ;)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 25, 2017, 01:27:59 PM
At the risk of drifting off topic, may I take this opportunity to point out that whilst we debate how many angels can dance on the head of a pin...
And I always thought that here on ASIF we were debating how many angels can dance on the remaining Arctic sea ice in September?  ;)

Pinhead size guaranteed...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 25, 2017, 06:11:21 PM
It would be an excellent topic if he had real experts instead of three bozos and an expert....

As a wag on Twitter pointed out, the Committee ought to be interrogating seeking the expert advice of another 96 climate scientists.

Smith comes to bury Mann, not to praise him.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on March 25, 2017, 11:04:44 PM
William Connolley replied to my criticism of Ding et al 2017 :

http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58495 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58495)

Quote
Having looked again, you appear to be correct. They’ve detrended on Z220, apparently on the assumption (which I can’t find stated) that Z200 must be “variability” but I can’t see any obvious reason to believe that. So, yes; by removing a pile of the forcing they’ve removed a pile of the result, i.e. less sea ice loss. Quite why this is supposed to be valid is, as you say, something of a mystery.

You’d expect the referees to pick this up -W
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 25, 2017, 11:24:21 PM
I've had the impression that since 2012 we've moved away from the dipole pattern which is so destructive for the ice, and the pattern discussed in this paper is kind of similar to the dipole.  To investigate further I've had a look at the Z200 height anomalies for every JJA year since 1996 over the Arctic, as analyzed in this paper.  I ignored years before 1995 as any appearance of the pattern before that time would reduce the trend.

This circulation pattern does not seem to form as a gradual trend, rather there is no sign of the pattern from 1996 to 2004, and then the pattern appears for the first time quite strong in 2005, and has appeared most years since.   The fact that the pattern appears abruptly suggests that the pattern is an unforced variation.  If the circulation change was forced by Co2 it would be more likely to be a gradual change.  Tipping point behavior might make for an abrupt change, but it would be hard to explain how the pattern then 'tipped back' in a few years since 2005.  More likely might be unforced variations that run opposite to the pattern up to 2004, and then switch in 2005.  This then suggests that the unforced variation was at least part of the change.

I was a little surprised that there is no noticeable evidence that the pattern ended in 2012.  There was an almost opposite pattern present in 2013, and also 2016, but the pattern was there in 2014, and quite strong in 2015.  The other year with an opposite pattern was 2006, and the other strong years were 2005, 2007 and 2011.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on March 26, 2017, 07:50:39 AM
I have emailed the authors Qinghua Ding, Eric Steig and Axel Schweiger for an opinion on my criticism of their paper.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 26, 2017, 08:50:34 AM
Well done, Rob. Keep us posted, if you can.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 26, 2017, 08:58:33 AM
I have emailed the authors Qinghua Ding, Eric Steig and Axel Schweiger for an opinion on my criticism of their paper.
I think that was the Right Thing To Do (tm) in this case, Rob.
But I don't expect any of them to bother answering your email, or much less discussing your criticism of their paper on a public forum, for three reasons:

*: See the thread Trump Administration Assaults on Science here on ASIF
http://forum.arctic-sea-ice.net/index.php/topic,1858.0.html (http://forum.arctic-sea-ice.net/index.php/topic,1858.0.html)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on March 27, 2017, 02:49:22 AM
Andrew, one of the "Four Agreements" (Google it) is : Don't make any assumptions.

I have receive a lengthy technical response from Qinghua (and a short note from Axel) which serves as a great start for a technical discussion.

Let me work out the logistics with them on how much and where they would like this discussion to be open to the public.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 27, 2017, 07:34:56 AM
Andrew, one of the "Four Agreements" (Google it) is : Don't make any assumptions.

I have receive a lengthy technical response from Qinghua (and a short note from Axel) which serves as a great start for a technical discussion.

Let me work out the logistics with them on how much and where they would like this discussion to be open to the public.

Rob, that's, to say the least, a surprising development!  :o
And your last phrase: what a cliffhanger!
OK, no more assumptions from me!  :-X
Good luck!

Note: I did Google "the Four Agreements". https://en.wikipedia.org/wiki/Don_Miguel_Ruiz
Very interesting!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 27, 2017, 09:00:04 AM
But I don't expect any of them to bother answering your email

As Rob has already pointed out, it didn't take long for your theory to be falsified!

For the record, I'm not a climate scientist but I have numerous email exchanges and even telephone conversations with people that are. Sometimes I even get to meet them in person:

https://youtu.be/UYAaQ4iwdtY (https://youtu.be/UYAaQ4iwdtY)

Persuading them to "stick their head above the parapet" in public is generally a little trickier. Kevin Anderson needs no such persuading however! Re your final paragraph, get the popcorn ready:

http://GreatWhiteCon.info/2017/03/a-report-on-the-state-of-the-arctic-in-2017/ (http://GreatWhiteCon.info/2017/03/a-report-on-the-state-of-the-arctic-in-2017/)

Quote
Friends, Romans, countrymen, lend me your ears;
Lamar Smith comes to bury Michael Mann, not to praise him
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 27, 2017, 10:11:02 AM
Jim,
As usual your latest post on your blog is a must-read, and I just read it with particular interest, because it is in many ways related to this thread.
I am happy that my expectation that none of the co-authors of the Ding et al paper would answer Rob's email, proved wrong. But we are still missing the substance of Ding's technical reply.
In any case, I am grateful to Rob for his critical analysis effort and for reaching out to these scientists. That Ding himself answered is already proof that Rob was indeed onto something.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 27, 2017, 02:40:55 PM
Here's an example of why it is sometimes embarrassing when malicious motives are assigned to scientists when they publish papers that can be spun by climate risk deniers. From the Stoat discussion on the Ding et al. paper, where the #2 comment stated that 'Qinghua Din lead author, has signed off on other papers with Willie “oilcan” Song, collector of 1+ million dollars from oil, energy & business PR propaganda poopers':

Quote
Qinghua Ding
Goleta,CA
2017/03/26

I am very disappointed to see #2 comment on our paper. But I really appreciate that Raymond said something for me and Eric fought back for me before I step in.

Here I only want to quickly respond to that suspicion.
The primary funding source of the paper is from NOAA.

Please check this if you want to know more

http://cpo.noaa.gov/ClimatePrograms/EarthSystemScience/ClimateVariabilityandPredictability/FundedProjects/tabid/435/u1168q/32303135/u1168c/5965617220496E697469616C6C792046756E646564/u1168m/equal/Default.aspx (http://cpo.noaa.gov/ClimatePrograms/EarthSystemScience/ClimateVariabilityandPredictability/FundedProjects/tabid/435/u1168q/32303135/u1168c/5965617220496E697469616C6C792046756E646564/u1168m/equal/Default.aspx)

I don’t know Willie Song. The main reason I was on that paper was that the paper focused on the global monsoon, a concept proposed by one of my early paper ( Wang and Ding 2005) with my Ph.D advisor ( Pro. Bin Wang). I helped the first author doing some analyses and so she put my name in the paper.I probably won’t check this blog again. If you have any further question, please reach me at my email address qinghua@ucsb.edu

Anyway, I'm looking forward to a response to Rob Dekker's critique.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 27, 2017, 11:14:07 PM
While Rob D. hasn't been very forthcoming with the author's responses, Eric Steig has commented over at Stoat's:

Quote
I gave up wasting my time with debates in the comments section of blogs a long time ago. One could spend all one’s time on it, leaving no time for anything serious. See here: http://www.realclimate.org/index.php/archives/2008/10/greenspan-einstein-and-reich/ (http://www.realclimate.org/index.php/archives/2008/10/greenspan-einstein-and-reich/)

I will just note that yes, I know what we did in the paper on which I am a coauthor, and no, I don’t agree with the statement that the “results don’t support the conclusions”. Most of the ideas RD has written here and elsewhere don’t make sense. For example, no, PV = nRT does not tell you how geopotential height responds to surface temperature! There is one aspect that might be worth discussing, which is that we assume, in effect, that most of the the trend in z200 is “natural variability”. (We don’t actually assume it — that’s a result of the analysis, but in the end it amounts to the same thing, pretty much). But this doesn’t come out of nowhere! it comes largely from our previous work published in 2014, showing that the trend in z200 is related to tropical forcing. To claim it is not natural variability you would have to show that the way that the spatial pattern of convection tropics has evolved in the last 30+ years is not natural variability. It has certainly [been] argued that it is not. Trenberth claimed to have to demonstrated an anthropogenic signal in tropical variability in 1997, during the massive 1997/1998 ENSO event, but events since then have largely negated that analysis (though it was a good analysis for the time). An honest assessment of the literature (see IPCC for example) would say that the jury remains out on that. To the extent that the decadal tropical changes ARE a forced response, then our estimate for the natural variability is an upper bound, which I think we were clear about in the paper.

Homework: Ding et al., 2014: http://www.nature.com/nature/journal/v509/n7499/full/nature13260.html (http://www.nature.com/nature/journal/v509/n7499/full/nature13260.html)

I also highly recommend Perlwitz et al., 2014.
http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-14-00095.1 (http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-14-00095.1)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 28, 2017, 03:23:23 AM
Thanks for that post ktonine.

Quote
For example, no, PV = nRT does not tell you how geopotential height responds to surface temperature!

I'm sorry but, what? This makes no sense to me, probably due to my ignorance in the topic. Let me review, can someone please point where I'm wrong?

From Wikipedia:

 PV = nRT

P is the pressure of the gas,
V is the volume of the gas,
n is the amount of substance of gas (also known as number of moles),
R is the ideal, or universal, gas constant
T is the absolute temperature of the gas.

If n and R remain constant T increases near the surface, then P or V (or both) must increase near the surface. If V increases near the surface wouldn't that result in changes in V higher up in the atmosphere? I imagine it would happen with a decreasing gradient but 200hPa seems low enough to be eventually affected.

It may be that the ideal gas law is a simplification that the models used in this experiment do not  use for practical reasons, but the physics seem clear to me. You change the temperature, you change the geopotential heights. The changes should have at least some influence all the way out to the stratosphere, but as it increases the impact of the changes decrease approaching 0.


Quote
An honest assessment of the literature (see IPCC for example) would say that the jury remains out on that.

I Imagine he refers to this : https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-5-2.html (https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-5-2.html)


Quote
To claim it is not natural variability you would have to show that the way that the spatial pattern of convection tropics has evolved in the last 30+ years is not natural variability.

Define natural variability. If he means free of human influence then he is the one who must prove that humans did not have a significant effect on the climate. Over the last 10,000 year we stopped the natural variability of the planet the slow cool down to the next ice age. Until the 1800's we prevented the planet from cooling as much as it would have without humans. After the 1800, we started actually warming the planet, contrary to what Milankovitch cycles indicate.

We didn't just warmed the planet, we changed a significant fraction of the surface of the planet making some places colder other warmer with their respective atmospheric changes. By razing forest we changed precipitation patterns and cloud formations that changed atmospheric patterns. We create aerosols that change the local temperatures to such magnitude that it has a visible effect on global temperatures.These and many more low altitude changes have small but real impacts in higher altitude currents. They must. How can they possibly not? Sure they are almost impossible to measure as they get lost in the noise but the changes must be there due to the most basic laws of physics.

Quote
To the extent that the decadal tropical changes ARE a forced response, then our estimate for the natural variability is an upper bound,

I would love to see the lower bound. My bet it is on 0% bound for natural variability, but it could very well be 30-40% lower bound due to random variability extrinsic to the arctic. Random variability !=Natural variability.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 28, 2017, 04:10:36 AM
Thanks for that post ktonine.

Quote
For example, no, PV = nRT does not tell you how geopotential height responds to surface temperature!

I'm sorry but, what? This makes no sense to me, probably due to my ignorance in the topic. Let me review, can someone please point where I'm wrong?

From Wikipedia:

 PV = nRT

P is the pressure of the gas,
V is the volume of the gas,
n is the amount of substance of gas (also known as number of moles),
R is the ideal, or universal, gas constant
T is the absolute temperature of the gas.

If n and R remain constant T increases near the surface, then P or V (or both) must increase near the surface. If V increases near the surface wouldn't that result in changes in V higher up in the atmosphere? I imagine it would happen with a decreasing gradient but 200hPa seems low enough to be eventually affected.

It may be that the ideal gas law is a simplification that the models used in this experiment do not  use for practical reasons, but the physics seem clear to me. You change the temperature, you change the geopotential heights. The changes should have at least some influence all the way out to the stratosphere, but as it increases the impact of the changes decrease approaching 0.


Quote
An honest assessment of the literature (see IPCC for example) would say that the jury remains out on that.

I Imagine he refers to this : https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-5-2.html (https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-5-2.html)


Quote
To claim it is not natural variability you would have to show that the way that the spatial pattern of convection tropics has evolved in the last 30+ years is not natural variability.

Define natural variability. If he means free of human influence then he is the one who must prove that humans did not have a significant effect on the climate. Over the last 10,000 year we stopped the natural variability of the planet the slow cool down to the next ice age. Until the 1800's we prevented the planet from cooling as much as it would have without humans. After the 1800, we started actually warming the planet, contrary to what Milankovitch cycles indicate.

We didn't just warmed the planet, we changed a significant fraction of the surface of the planet making some places colder other warmer with their respective atmospheric changes. By razing forest we changed precipitation patterns and cloud formations that changed atmospheric patterns. We create aerosols that change the local temperatures to such magnitude that it has a visible effect on global temperatures.These and many more low altitude changes have small but real impacts in higher altitude currents. They must. How can they possibly not? Sure they are almost impossible to measure as they get lost in the noise but the changes must be there due to the most basic laws of physics.

Quote
To the extent that the decadal tropical changes ARE a forced response, then our estimate for the natural variability is an upper bound,

I would love to see the lower bound. My bet it is on 0% bound for natural variability, but it could very well be 30-40% lower bound due to random variability extrinsic to the arctic. Random variability !=Natural variability.

Sorry but dynamic variability = random variability = natural variability. The variability of the dynamic earth system. There is no unnatural random variability.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 28, 2017, 04:11:23 AM
Or else...noise
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 28, 2017, 04:48:59 AM
Quote
Sorry but dynamic variability = random variability = natural variability. The variability of the dynamic earth system. There is no unnatural random variability.

I could not disagree more. Dynamic variability is not random. Dynamic variability is perfectly determined by a set of forces. However, dynamic variability in the climate system is so complex that the only way for us to understand it is through tools like the concept of randomness.

 There is a natural component to the variability of the climate system. That natural variability is given by things like the topography of the planet, orbital changes, solar variation, the chemical composition of the atmosphere, life etc. It is also not random, it is just so complex that it seems random.

There is also a man made component to the dynamic variability of the climate system.  It is also so complex that it seems random.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 28, 2017, 04:51:30 AM
Or else...noise

There is no such thing as noise, only limits of the models.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on March 28, 2017, 05:44:13 AM
We are now down to philosophy. In practical terms, the question is whether the circulation changes are "random" in that there is no underlying trend in them, even if influenced by human activities. In such a case, sea ice should rebound when the random dice roll the other way. OTOH, if the circulation changes have an underlying noisy trend due to human activities, then sea ice ain't coming back.
(My own worthless opinion is in the second camp)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on March 28, 2017, 07:00:43 AM
OK. Here an update on the reply from the authors of Ding et al 2017.
Qinghua has indicated that he is not interested in an "ongoing blog-based discussion, which can quickly turn into a huge time sink".

I can't disagree with him, but also I did not get any word on how much of his (now two lengthy technical) replies I am allowed to post publicly. So, for the moment, I won't post any.

However, Eric Steig decided to post a comment on William Connolly's "stoat" site, where he posted that he found that my comments "don't make sense".
So I decided to reply to that publicly :

http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58573 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58573)

Quote
Eric, thank you for your reply.
I’m sorry that my comments “don’t make sense”. Let me clarify my points in better detail here.

William mentioned that “The point of the trend in z200 is “natural variability” is indeed the point that RD is questioning” and that is certainly a point of concern. After all, we KNOW that at least a part of the atmospheric temperature increase is due to AGW, which MUST have put an imprint on geopotential height over the Arctic. Jennifer Francis theory of wavy jetstreams due to reduced geopotential height difference between the tropics and the Arctic is based on that. Are you now saying that that theory is wrong ?
If not, then at least a part of trend in geopotential height increase (Z200) since 1979 must be anthropogenic.

But in fact the core of my argument goes one step further :

I claim that your “regression coefficient” in Experiment 6 eliminates ALL trends, natural or anthropogenic. And thus, that you essentially kept the climate constant in Experiment 6.

To see that, check the regression formula you use for Exp-6 :

B(x, y, t) = β(x, y) × Z200 GL (t) (1)

Here, β(x, y) is the regression coefficient between Z200-GL and the variable under consideration, and B(z,y,t) is the “forcing” that you later subtract from the ERA data during summer.
Now, the regression coefficient is very good in finding trends.
So even if the correlation of Z200-GL and the variable (say “temperature”) is not very good (like further away from Greenland) the regression coefficient will still find a ‘trend’, and thus the “forcing” you subtract for Exp-6 will still be pretty darn close to the linear relation we expect to see from the ideal gas law.

Qinghua has all the data available, so could you please ask him to reproduce the “adjusted forcing” for Exp-6 for, say the temperature variable north of 70deg, and check if it still has a trend since 1979 ? I claim it doesn’t, since the regression method eliminated it.

And that means that all you have calculated (between Exp-5 and Exp-6) is the influence of climate change over the JJA period (60%) which means the remaining 40% was caused by climate change over the other 9 months.

Which is an interesting conclusion, but positively doesn’t have anything to do with “natural” or “anthropogenic” causes of the trend in Z200-GL.

I am now pretty convinced that I understand exactly what Ding et al 2017 did, and that I'm right that what they calculated (between Exp-5 and Exp-6) is the influence of climate change over the JJA period (60%) which means the remaining 40% was caused by climate change over the other 9 months.

Which is an interesting conclusion, but positively doesn’t have anything to do with “natural” or “anthropogenic” causes of the trend in Z200-GL.

And thus they can no longer claim that "Internal variability dominates the Arctic summer circulation trend" nor that it "may be responsible for about 30–50% of the overall decline in September sea ice since 1979.".

There simply is no evidence of that.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 28, 2017, 12:15:51 PM
Or else...noise

There is no such thing as noise, only limits of the models.
 

I think we are talking past each other... The notion of randomness and noise is perfectly compatible with deterministic dynamical systems.  You can follow every motion of every molecule or describe an average behavior using the notions of random walk and noise.  Brownian motion is fully deterministic yet can be perfectly described as thermal noise. Turbulence is another example. White noise is a Gaussian distribution....  all these are convenient analytical tools.  Volcanoes which are a source of climate variability are perfectly deterministic but can also be described by a random or stochastic process.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 28, 2017, 12:28:31 PM
OK. Here an update on the reply from the authors of Ding et al 2017.
Qinghua has indicated that he is not interested in an "ongoing blog-based discussion, which can quickly turn into a huge time sink".
...
The latest development is that, Qinghua Ding seems to have changed his position somewhat, because he posted the following in the Stoat blog (link below):
Quote
Qinghua Ding
Goleta,CA
2017/03/28

I received the third email from Rob and then test his idea tonight. Actually, we did all these calculations before we implemented Exp. 6. The test shows we still have 35% of trend retained after that Z200-GL influence is removed. I have sent a figure to Rob. The original trend of LW ( the purple curve in Fig. 4 of the paper) from 1979 to 2014 is 2w/m2/decade. The modified one still owns a 0.7W/m2/decade trend.

link: http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58578 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58578)

Unfortunately, at this point this creates a mess, because:

Eric's latest and probably last comment on the Stoat blog also confuses matters further, because first he dismisses Rob's critical analysis as "nonsense", but then he takes his time to repeat that "we assume, in effect, that most of the trend in Z200 is "natural variability"."

Which is exactly the assumption that many here have expressed serious doubts about.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 28, 2017, 12:36:31 PM
OK. Here an update on the reply from the authors of Ding et al 2017.
Qinghua has indicated that he is not interested in an "ongoing blog-based discussion, which can quickly turn into a huge time sink".
...
The latest development is that, Qinghua Ding seems to have changed his position somewhat, because he posted the following in the Stoat blog (link below):
Quote
Qinghua Ding
Goleta,CA
2017/03/28

I received the third email from Rob and then test his idea tonight. Actually, we did all these calculations before we implemented Exp. 6. The test shows we still have 35% of trend retained after that Z200-GL influence is removed. I have sent a figure to Rob. The original trend of LW ( the purple curve in Fig. 4 of the paper) from 1979 to 2014 is 2w/m2/decade. The modified one still owns a 0.7W/m2/decade trend.

link: http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58578 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58578)

Unfortunately, at this point this creates a mess, because:
  • It's not at all clear whether Qinghua Ding concedes to a mistake in the methodology of the Ding et al paper.
  • We don't have access to the contents of Rob's three emails to Ding nor to the two lengthy technical replies from Ding to Rob.

Eric's latest and probably last comment on the Stoat blog also confuses matters further, because first he dismisses Rob's critical analysis as "nonsense", but then he takes his time to repeat that "we assume, in effect, that most of the trend in Z200 is "natural variability"."

Which is exactly the assumption that many here have expressed serious doubts about.
 

which brings us to the realisation that nobody is fully free of confirmation bias.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: josh-j on March 28, 2017, 01:42:08 PM
Eric's latest and probably last comment on the Stoat blog also confuses matters further, because first he dismisses Rob's critical analysis as "nonsense", but then he takes his time to repeat that "we assume, in effect, that most of the trend in Z200 is "natural variability"."

Which is exactly the assumption that many here have expressed serious doubts about.
(emphasis mine)

I think it is worth taking the bolded section above in context:

Quote from: Eric Stein
There is one aspect that might be worth discussing, which is that we assume, in effect, that most of the the trend in z200 is “natural variability”. (We don’t actually assume it — that’s a result of the analysis, but in the end it amounts to the same thing, pretty much). But this doesn’t come out of nowhere! it comes largely from our previous work published in 2014, showing that the trend in z200 is related to tropical forcing.

The 2014 paper is, I believe, the following:

Ding, Q. H. et al. Tropical forcing of the recent rapid Arctic warming in northeastern Canada and Greenland. Nature 509, 209-212 (2014).

From the abstract:
Quote
Here we show that the recent warming in this region is strongly associated with a negative trend in the North Atlantic Oscillation, which is a response to anomalous Rossby wave-train activity originating in the tropical Pacific. Atmospheric model experiments forced by prescribed tropical sea surface temperatures simulate the observed circulation changes and associated tropospheric and surface warming over northeastern Canada and Greenland. Experiments from the Coupled Model Intercomparison Project Phase 5 (ref. 16) models with prescribed anthropogenic forcing show no similar circulation changes related to the North Atlantic Oscillation or associated tropospheric warming. This suggests that a substantial portion of recent warming in the northeastern Canada and Greenland sector of the Arctic arises from unforced natural variability.

I think if we have doubts about an assumption of natural variability in Z200 (I have no idea myself), it might worth looking at this paper, not just the 2017 one. I could not find it at a glance outside of the paid Nature publication however.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 28, 2017, 01:48:06 PM
Jim,

As usual your latest post on your blog is a must-read, and I just read it with particular interest, because it is in many ways related to this thread.

Andrew - Thank you for your kind words. It may therefore interest you to learn that my very latest post also "is in many ways related to this thread."

"Shock News! Alice F. Convicted in WUWT Show Trial!! (http://greatwhitecon.info/2017/03/alice-f-convicted-in-wuwt-show-trial/)"

Quote
What is one to do, then, when Anthony Watts publishes these scurrilous allegations about one's character by the pseudonymous "Sunsettommy" under an article by David Middleton on a topic under much discussion (http://greatwhitecon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/) here?

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 28, 2017, 03:41:38 PM
The latest chapter and hopefully the final one.

However, Eric Steig decided to post a comment on William Connolly's "stoat" site, where he posted that he found that my comments "don't make sense".

Quote
Eric, thank you for your reply.
I’m sorry that my comments “don’t make sense”. Let me clarify my points in better detail here.
....
Qinghua has all the data available, so could you please ask him to reproduce the “adjusted forcing” for Exp-6 for, say the temperature variable north of 70deg, and check if it still has a trend since 1979 ? I claim it doesn’t, since the regression method eliminated it.
...

I am now pretty convinced that I understand exactly what Ding et al 2017 did, and that I'm right that what they calculated (between Exp-5 and Exp-6) is the influence of climate change over the JJA period (60%) which means the remaining 40% was caused by climate change over the other 9 months.

Which is an interesting conclusion, but positively doesn’t have anything to do with “natural” or “anthropogenic” causes of the trend in Z200-GL.

And thus they can no longer claim that "Internal variability dominates the Arctic summer circulation trend" nor that it "may be responsible for about 30–50% of the overall decline in September sea ice since 1979.".

There simply is no evidence of that.

Quinha Ding: "Actually, we did all these calculations before we implemented Exp. 6. The test shows we still have 35% of trend retained after that Z200-GL influence is removed. I have sent a figure to Rob. The original trend of LW ( the purple curve in Fig. 4 of the paper) from 1979 to 2014 is 2w/m2/decade. The modified one still owns a 0.7W/m2/decade trend."

Rob based his claim on the  idea that the regression factor removed all of the trend.  It did not.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 28, 2017, 04:13:12 PM
I could not find it at a glance outside of the paid Nature publication however.

http://geog.ucsb.edu/~qinghua/pdf/24.pdf (http://geog.ucsb.edu/~qinghua/pdf/24.pdf)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 28, 2017, 07:46:23 PM
I could not find it at a glance outside of the paid Nature publication however.

http://geog.ucsb.edu/~qinghua/pdf/24.pdf (http://geog.ucsb.edu/~qinghua/pdf/24.pdf)
Thank you, jai mitchell.
I have just glanced through the 2014 paper, and it seems like very much a prelude to the 2017 one: same methodology, similar assumptions (as far as I can see) and a very similar conclusion.
Quoting from the 2014 paper:
Quote
"The results from the ECHAM experiments forced by observed SST, together with the ensemble average of the historical simulations of the CMIP5 models, suggest that about half of the observed warming in northeastern Canada and Greenland is due to a uniform warming of the
entire Arctic(directly attributable to anthropogenic forcing);the other half is due to a wave train of circulation anomalies that extends from the central tropical Pacific to Canada, and which is forced by trends in the tropical Pacific SST."

However, the claim they make in the abstract of the 2014 paper is directly contradicted by recent research into the demise of the Barnes Ice Cap.
http://onlinelibrary.wiley.com/doi/10.1002/2016GL072394/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2016GL072394/abstract)

As far as I know, in climate science just as in other sciences, physical evidence is stronger proof than any conclusions derived from models. Which brings us back to the methodology used by Ding et al in both the 2014 and 2017 papers, the assumptions they make, the models they chose to use, and the conclusions they reach from their model simulations.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 28, 2017, 07:57:38 PM

However, the claim they make in the abstract of the 2014 paper is directly contradicted by recent research into the demise of the Barnes Ice Cap.
http://onlinelibrary.wiley.com/doi/10.1002/2016GL072394/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2016GL072394/abstract)

Oh c'mon Andrew - give it up.  Directly contradicted? <snip; I'm not against cursing per se, but this is uncalled for and unnecessary; N.>.  Nothing in that paper directly contradicts Ding et al. I suspect you haven't even read the paper - just the abstract.

It's the sun! It's the wind! It's cosmic rays! It's clouds!  Sound familiar?  It's what we hear from deniers whenever you mention CO2.  You are sounding just like them - simply unable to admit you were wrong and continually searching for some *other* reason to deny it might actually be natural variability.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 28, 2017, 08:12:09 PM
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.

these papers, however DO show that 1. Anthropogenic aerosols are the primary driver of north atlantic SST and that 2. North Atlantic SST is determined by NAO conditions, ergo, NAO variability is primarily driven by Aerosol emissions.

The Ding paper only reinforces this as his teleconnection to tropical pacific variability is ALSO well understood to be primarily driven by anthropogenic aerosols.

see:

Booth et al. (2012)
Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability
http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf (http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf)

“Individually, volcanoes and aerosols explain 23% and 66% of the temporal multidecadal variability (10 year smoothed) of the detrended NASST (Figure S5). Combining both contributions, 76% (80% after inclusion of mineral dust aerosols) of the simulated variance is explained.”

Miettinen et al. (2011)
North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years
https://www.researchgate.net/publication/227298859_North_Atlantic_sea_surface_temperatures_and_their_relation_to_the_North_Atlantic_Oscillation_during_the_last_230_years (https://www.researchgate.net/publication/227298859_North_Atlantic_sea_surface_temperatures_and_their_relation_to_the_North_Atlantic_Oscillation_during_the_last_230_years)

“The aSST record and the August North Atlantic Oscillation (aNAO) index show similar multidecadal-scale variability indicating a close coupling between the oceanic and atmospheric patterns. The aSST record shows a negative correlation with the aNAO indicating cold aSST during the positive aNAO trend and vice versa. Results suggest that the wind driven variation in volume fluxes of the North Atlantic surface waters could be the major mechanism behind the observed relationship. North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years.”
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Darvince on March 28, 2017, 08:26:50 PM
angry
If a certain poster is bothering you so much, there is an ignore feature that allows you to hide people's posts. However, before the posts are hidden, you must check the "Hide messages posted by users on my ignore list" checkbox under Profile > Modify Profile > Look and Layout.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: bbr2314 on March 28, 2017, 11:39:41 PM
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.

these papers, however DO show that 1. Anthropogenic aerosols are the primary driver of north atlantic SST and that 2. North Atlantic SST is determined by NAO conditions, ergo, NAO variability is primarily driven by Aerosol emissions.

The Ding paper only reinforces this as his teleconnection to tropical pacific variability is ALSO well understood to be primarily driven by anthropogenic aerosols.

see:

Booth et al. (2012)
Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability
http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf (http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf)

“Individually, volcanoes and aerosols explain 23% and 66% of the temporal multidecadal variability (10 year smoothed) of the detrended NASST (Figure S5). Combining both contributions, 76% (80% after inclusion of mineral dust aerosols) of the simulated variance is explained.”

Miettinen et al. (2011)
North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years
https://www.researchgate.net/publication/227298859_North_Atlantic_sea_surface_temperatures_and_their_relation_to_the_North_Atlantic_Oscillation_during_the_last_230_years (https://www.researchgate.net/publication/227298859_North_Atlantic_sea_surface_temperatures_and_their_relation_to_the_North_Atlantic_Oscillation_during_the_last_230_years)

“The aSST record and the August North Atlantic Oscillation (aNAO) index show similar multidecadal-scale variability indicating a close coupling between the oceanic and atmospheric patterns. The aSST record shows a negative correlation with the aNAO indicating cold aSST during the positive aNAO trend and vice versa. Results suggest that the wind driven variation in volume fluxes of the North Atlantic surface waters could be the major mechanism behind the observed relationship. North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years.”
This is very interesting to me. One thing I have noticed since studying history is the seeming correlation between the World Wars and brutally cold winters in Europe. But perhaps it is not merely correlation, but causation?

If aerosols are the primary drivers of global atmospheric patterns then it would stand to reason that as human industrial manufacturing kicks into its highest gears (i.e., during wartime), the plumes of aerosols would drift north forcing more high-latitude "blocking" and consequently allowing much colder air to enter the continents where people actually live.

We saw this happen both during World Wars I and II, especially at the onset of WWII, when 1939-40 was the most brutal winter across much of Europe since the end of the nineteenth century.

http://www.nature.com/nature/journal/v145/n3671/abs/145376a0.html (http://www.nature.com/nature/journal/v145/n3671/abs/145376a0.html)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 29, 2017, 01:44:14 AM
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.
...
jai mitchell, did you check where the Barnes ice cap is located? It's on Baffin Island, just across from Greenland. See the attached image.

According to the paper by Gilbert et al, the Barnes ice cap - a remnant from the last ice age - has stabilized some two thousand years ago - and they have physical evidence that it hasn't melted at all since then (cosmogenic radionuclides), despite the 2,000 or so cycles of Arctic sea ice melting/freezing around the Baffin Island. But now, unprecedented warmth in the northeastern Canada and Greenland region is causing the disappearance of the Barnes ice cap.

If half the warming in the northeastern Canada and Greenland region is - as the Ding et al 2014 paper suggests - due to natural variability, how come this "natural variability" has not once affected the Barnes ice cap in the last 2,000 years?

The problem with Arctic sea ice is that we only have a 40 years satellite record, besides the fact that Arctic sea ice comes and goes every year. So the claim by Ding et al that the recent demise of the Arctic sea ice is in a large part due to "natural climate variability", cannot be contradicted with historical data. But not so with the Barnes ice cap. We have a 10,000+ years record - with proper physical evidence - of its existence, and a 2,000+ years record of its relative stability, during which NO "natural variability" climate component affected it.

I fully agree with you that the disappearance of Arctic sea ice is 110% the result of anthropogenic forcing. I would say the same applies to the recent warming of the northeastern Canada and Greenland region, where the Barnes ice cap is located.

The paper by Gilbert et al about the Barnes ice cap supports the assertion that anthropogenic forcing is responsible for the unprecedented warming in the region, "unprecedented" being the key word here. It directly contradicts the claim in the Ding et al 2014 paper that (quoting from the abstract) "... a substantial portion of recent warming in the northeastern Canada and Greenland sector of the Arctic arises from unforced natural variability."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Peter Ellis on March 29, 2017, 11:48:54 AM
If half the warming in the northeastern Canada and Greenland region is - as the Ding et al 2014 paper suggests - due to natural variability, how come this "natural variability" has not once affected the Barnes ice cap in the last 2,000 years?

Uh, this is trivial maths.

If warming from natural variability in the last 40 years is X degrees, and this is typical of the longer-term record (2,000 -10,000 years), and then climate change adds another X, then all the following are true:

1)  Recent warming (X + X = 2X) is unprecedented
2)  Recent warming is only 50% due to climate change, and 50% due to natural variability.
3)  Recent total warming is more than the Barnes ice sheet has seen before, and is sufficient to destabilise it. 

Fundamentally, the straw does not need to outweigh the camel in order to break its back.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 29, 2017, 12:39:19 PM
If half the warming in the northeastern Canada and Greenland region is - as the Ding et al 2014 paper suggests - due to natural variability, how come this "natural variability" has not once affected the Barnes ice cap in the last 2,000 years?

Uh, this is trivial maths.
...
Fallacious argument. You are assuming that the present warming due to natural climate variability is by far the largest in over 2,000 years, in other words you just played Russian roulette every summer in over 2000 years, survived unscathed for over 1960 years but died continuously the last 40 years. Not very likely, is it?
Warming (in the northeastern Canada and Greenland region) due to "natural climate variability" has peaked many times over the 2,000 years covered by physical evidence (the cosmogenic nuclides), and it was not enough to affect the Barnes ice cap.
But recent warming is definitely signaling the demise of the Barnes ice cap. Attribution of a large part of this unprecedented warming to anything else than AGW contradicts the very definition of "natural climate variability" as a random phenomenon and, is just bad science. And when this claim is based on model simulations, just an unwarranted use of models. Which is exactly the reason I and others have been questioning the fact that the models-based methodology of Ding et al does not support their conclusions.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 29, 2017, 02:19:56 PM
Fallacious argument.

Excuse me? Peter was playing "what if?".

In particular, "what if natural variability is exactly the same today as it has been for the last 10,000 years?"
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 29, 2017, 04:20:34 PM
Can anyone think of a physical  mechanism that can account for 60% of the sea ice loss experienced from 1979 to 2014?  Such mechanism should reflect the very small loss rate from 1979-2007 and an acceleration from 2007-today.

Since the arctic is currently at minimum levels such mechanism may very well be at a maximum impact right now.

Quote
Recent total warming is more than the Barnes ice sheet has seen before, and is sufficient to destabilise it. 

If the first X varied naturally for thousands of years without destabilizing the ice sheet and only when humans added the second X was the ice destabilized, the ice loss is 100% due to to human warming.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Tor Bejnar on March 29, 2017, 04:53:10 PM
...
If the first X varied naturally for thousands of years without destabilizing the ice sheet and only when humans added the second X was the ice destabilized, the ice loss is 100% due to to human warming.
I don't want to defend Ding et al.  But I do want to defend Peter.

2X 'obviously' exceeded some tipping point with relation to the Barnes Ice Sheet.  A single X could have had little noticeable affect. 

Separately, a single X (according to Ding et al) affects Arctic ice about as much as does AGW.  Although Arctic ice and Barnes ice are affected by most of the same forces, there are differences in degree (winds at altitude vs winds at sea level, insolation varies with latitude, ocean currents [huge difference]), so the affect of any one change could easily affect the response of the two icy entities differently.

I, too, question (the unread by me) Ding et al.  There were driftwood studies and Arctic Ocean ice shelves that suggest what has happened to Arctic ice these past 30 years is seriously unprecedented these past several thousand years.  I'd hazard a guess of a factor of 10, rather than 2.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 29, 2017, 07:27:04 PM
...
2X 'obviously' exceeded some tipping point with relation to the Barnes Ice Sheet.
...

Contrarily to the immense  and immensely complex Arctic sea ice, the Barnes ice cap is just that: a large mass of ice that has remained in place, unchanged in size, for more than 2,000 years. Without the melting/freezing cycles that the Arctic sea ice suffers every year.

The concept of "tipping point" does not apply to the Barnes ice cap. There are no positive feedbacks that would lead to the passing of a "tipping point" leading to its melting. It's just a mass of ice, not a complex system. And we have physical evidence that it has NOT melted by half its present rate of melt (your 2X divided by 2, i.e. the model-derived "natural variability" caused melt) over the last 2,000-40 years. So there is no evidence of a 1X "natural variability" warming over that period. Just like there is no evidence of an invisible flying spaghetti monster, that would NOT have blown hot air over the Barnes ice cap during this period of approximately 2,000 years, but suddenly woke up 40 years ago - by an extraordinary coincidence, when AGW got going - and contributed by 1X to its present rate of melt.

Sorry, but physical evidence trumps model-derived attribution claims, in this case. And simple logic indicates we don't need an invisible flying spaghetti monster nor a model-derived "natural variability" factor to explain the demise of the Barnes ice cap or the recent extraordinary warming of the northeastern Canada and Greenland region.

https://en.wikipedia.org/wiki/Flying_Spaghetti_Monster
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 29, 2017, 07:45:29 PM
Can anyone think of a physical  mechanism that can account for 60% of the sea ice loss experienced from 1979 to 2014?
...

Archimid, there is a single physical mechanism that melts ice, and it's energy (heat). And we know that the Arctic is warming 2.5~3 x faster than the rest of the world.
So the question is, how does heat from lower latitudes reach the Arctic? There are only two possible ways: either the oceans or the atmosphere. The relative percentages are irrelevant. We just know that this extra heat is due to the present energy imbalance of our planet as a whole (AGW).
In other words, whatever ocean currents or atmospheric circulation patterns you want to invoke to explain the demise of the Arctic sea ice, the heat/energy being transported to the Arctic is the result of an anthropogenic forcing, and certainly NOT "natural climate variability".
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 29, 2017, 11:18:54 PM
AndrewB, I agree with you but I was hoping that I was missing something that the "natural variability"  folks know.

An example of what I'm looking for would be something like the PDO. if we assume that the variability of the PDO (its sign, magnitude and frequency) hasn't been influenced by anthropogenic forcings (a big if) then the PDO would be a natural variation. But as you well said, even if the PDO varies naturally it still has to go through the atmosphere to get to teh Arctic, which we already know it has changed due to anthropogenic forcings.

Then you have the Arctic. Since 1979 it has been in decline yet the PDO has oscillated several times. It has been mostly positive for decades and mostly negative for decades. Yet through positives and negatives the arctic decline continues. At most, the natural variability of the PDO is responsible for the rate of melt. During negative cycles the arctic melts slowly and during a positive cycle it melts faster. But it melts either way. Thus 100% of the melt is anthropogenic, but the rate of melt has natural variation in it.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Tor Bejnar on March 29, 2017, 11:55:59 PM
...
The concept of "tipping point" does not apply to the Barnes ice cap.
...
I say it does!  The ice cap wasn't melting faster than it was expanding for a very long time, and now it is.  (And what caused approximately 100% of this change, I'm sure, is AGW.)

What I attempted to communicate earlier is that changes in forces (e.g., CO2) within a system (e.g., the icy Arctic) affect different parts of the system (sea ice, ice caps) differently.  Some things are like a canary in a coal mine - are affected obviously and quickly by certain changes - and others are not apparently affected.  Ice caps are affected less than (or more slowly than) sea ice by AGW.  (But a volcano erupting under an ice cap will melt more ice than a similar volcano erupting under the CAB.)

As to figuring out what non-AGW variability is affecting Arctic sea ice, there is "weather" - functionally good-for-melting seasons vs. good-for-keeping-ice-around seasons.  The generic AGW conditions were similar, but the Arctic responses in 2007 and 2012 were very different from 2013 and 2014.  If an 'average' season is half-way between these two pairs, what metric would one use to derive percentages (low points, high points, area, volume, some combination???)?  My biggest problem with this approach is that weather patterns are changing because of AGW.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 30, 2017, 12:56:40 AM
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.

these papers, however DO show that 1. Anthropogenic aerosols are the primary driver of north atlantic SST and that 2. North Atlantic SST is determined by NAO conditions, ergo, NAO variability is primarily driven by Aerosol emissions.

The Ding paper only reinforces this as his teleconnection to tropical pacific variability is ALSO well understood to be primarily driven by anthropogenic aerosols.

see:

Booth et al. (2012)
Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability
http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf (http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf)

“Individually, volcanoes and aerosols explain 23% and 66% of the temporal multidecadal variability (10 year smoothed) of the detrended NASST (Figure S5). Combining both contributions, 76% (80% after inclusion of mineral dust aerosols) of the simulated variance is explained.”

Miettinen et al. (2011)
North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years
https://www.researchgate.net/publication/227298859_North_Atlantic_sea_surface_temperatures_and_their_relation_to_the_North_Atlantic_Oscillation_during_the_last_230_years (https://www.researchgate.net/publication/227298859_North_Atlantic_sea_surface_temperatures_and_their_relation_to_the_North_Atlantic_Oscillation_during_the_last_230_years)

“The aSST record and the August North Atlantic Oscillation (aNAO) index show similar multidecadal-scale variability indicating a close coupling between the oceanic and atmospheric patterns. The aSST record shows a negative correlation with the aNAO indicating cold aSST during the positive aNAO trend and vice versa. Results suggest that the wind driven variation in volume fluxes of the North Atlantic surface waters could be the major mechanism behind the observed relationship. North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years.”

Your argument might work if Aerosol was 100% of NA variability, or if the proposed link between Arctic ice cover and variability being discussed in this thread was about the Atlantic instead of the Pacific.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 30, 2017, 01:11:49 AM

The Ding paper only reinforces this as his teleconnection to tropical pacific variability is ALSO well understood to be primarily driven by anthropogenic aerosols.

see:

Booth et al. (2012)
Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability
http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf (http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf)

“Individually, volcanoes and aerosols explain 23% and 66% of the temporal multidecadal variability (10 year smoothed) of the detrended NASST (Figure S5). Combining both contributions, 76% (80% after inclusion of mineral dust aerosols) of the simulated variance is explained.”


Your argument might work if Aerosol was 100% of NA variability, or if the proposed link between Arctic ice cover and variability being discussed in this thread was about the Atlantic instead of the Pacific.

I'm also not sure when volcanoes became part of anthropogenic emissions.  Not all aerosols are anthro - just sayin'
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on March 30, 2017, 01:19:16 AM

Then you have the Arctic. Since 1979 it has been in decline yet the PDO has oscillated several times. It has been mostly positive for decades and mostly negative for decades. Yet through positives and negatives the arctic decline continues. At most, the natural variability of the PDO is responsible for the rate of melt. During negative cycles the arctic melts slowly and during a positive cycle it melts faster. But it melts either way. Thus 100% of the melt is anthropogenic, but the rate of melt has natural variation in it.

The PDO has only oscillated once.  Maybe the start of a second oscilation if it turns out that the warm PDO for the last few years is a real warm phase and not a false alarm.  A trend analysis (http://www.woodfortrees.org/plot/jisao-pdo/from:1979/plot/jisao-pdo/from:1979/trend) on PDO data since 1979 reveals a substantial downward trend. 

Although I don't think it can be as simple as cool PDO implies fast melt, otherwise the relationship would have been discovered long ago.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 30, 2017, 04:16:54 AM
The PDO has only oscillated once.  A trend analysis (http://www.woodfortrees.org/plot/jisao-pdo/from:1979/plot/jisao-pdo/from:1979/trend) on PDO data since 1979 reveals a substantial downward trend. 

I stand corrected. I was thinking of the century dataset when I was speaking of the dataset after 1979.

Quote
Although I don't think it can be as simple as cool PDO implies fast melt, otherwise the relationship would have been discovered long ago.

I think a warm PDO implies fast melt because warmer air temperatures  will eventually teleconnect with the Arctic.  The signal of the PDO could not be detected in the 20th century because there was a thick ice cap and the planet was cold enough. At some point near the turn of the century the ice got too small and/or the planet too warm. In a warmer earth with much less ice, the signal of the PDO has a greater impact on air temperatures and in turn, on the ice.

 
Quote
Maybe the start of a second oscilation if it turns out that the warm PDO for the last few years is a real warm phase and not a false alarm

The downward trend of the PDO is clear and I think that, as you say, the current positive phase is not the real positive phase. I think the PDO is to a great extent  solar cycle driven (http://woodfortrees.org/plot/sidc-ssn/scale:30/offset:-2100/from:1979/plot/jisao-pdo/scale:1500/from:1979/offset:400).  The Sun is schedule for weaker cycles until it reaches a minimum in 2030.  Unless something big changes (like aerosols) the PDO should enter a cooler phase next year or the one after.

The problem is that the last time we got a cool phase (the "hiatus") there was more ice and the air temperatures were colder, yet the melt continued. I have no reason to think that during the (hopefully) coming cooler phase the melt will stop and the ice recover to levels of the 20th century. If it was melting .1 C colder and many thousands of km3 of ice ago, it will keep melting even if we enter another "hiatus". 

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 30, 2017, 08:45:44 AM
...
The concept of "tipping point" does not apply to the Barnes ice cap.
...
I say it does!  The ice cap wasn't melting faster than it was expanding for a very long time, and now it is.  (And what caused approximately 100% of this change, I'm sure, is AGW.)
...

We essentially agree then.  ;)

I would point you to a tipping point page on Wikipedia but imho the Wikipedia page on climate tipping points is not that good. Keeping it simple: there are no "tipping points" for a simple chunk of ice, however large it may be such as the Barnes ice cap: it's not a complex system, there are no positive feedbacks, and it melts linearly to the amount of energy/heat you apply to it.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Adam Ash on March 30, 2017, 09:25:21 AM
'...melts linearly...'  Mmm.  Isn't it likely that the ratio of surface area exposed to warm air versus volume of remaining ice will increase as the melting progresses, giving a rather more exponential melt rate versus linear for given temperature conditions? 

Sure, not a 'tipping point', but classic Seneca Cliff decline would seem likely, as the next best (or worst) thing.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 30, 2017, 10:47:32 AM
'...melts linearly...'  Mmm.  Isn't it likely that the ratio of surface area exposed to warm air versus volume of remaining ice will increase as the melting progresses, giving a rather more exponential melt rate versus linear for given temperature conditions? 

Sure, not a 'tipping point', but classic Seneca Cliff decline would seem likely, as the next best (or worst) thing.


Without feedbacks the melting rate depends on the heat imbalance. If there is a constant imbalance x Watts then the mass rate of melting will be constant and the mass decrease linear. If there is a constant temperature difference then the melting rate will be proportional to the external surface area and it will slow down with time.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 30, 2017, 10:53:21 AM
'...melts linearly...'  Mmm.  Isn't it likely that the ratio of surface area exposed to warm air versus volume of remaining ice will increase as the melting progresses, giving a rather more exponential melt rate versus linear for given temperature conditions? 

Sure, not a 'tipping point', but classic Seneca Cliff decline would seem likely, as the next best (or worst) thing.

That's the heat(energy) transfer rate that varies according to various parameters, such as humidity, wind, etc. The linear relationship between melt and energy still holds, because it's just a basic physics law (if it takes X Joules to melt 1kg of ice, it takes 2X Joules to melt 2kg of ice, etc).
The end of my phrase, which you have somehow cut away, indicates this clearly:
"... it [a chunk of ice] melts linearly to the amount of energy/heat you apply to it."

But that's nitpicking on details. My point is that there are no "tipping points" to be considered in the case of the Barnes ice cap, so it's not like equal shares of "natural climate variability" + AGW have suddenly triggered a positive feedback which is leading to the demise of the Barnes ice cap.

Again, just to keep it simple: the Barnes ice cap is disappearing because AGW has caused 100% of the unprecedented recent warming observed in the northeastern Canada and Greenland region. That's what the physical evidence over more than 2,000 years shows.
If Ding et al claim otherwise because they derive some unwarranted conclusions from their model simulations, they are wrong.
And since they used the same methodology and derived similar conclusions in their 2017 paper that attributes 30~50% of the recent Arctic sea ice decline (in September) to "natural climate variability" (in the months of June July August), they are wrong about that too.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 30, 2017, 11:35:44 AM
Andrew.  You have a gut feeling they are wrong. You cannot prove they are wrong.

Not every paper out there will be right but they all contribute, if nothing else, showing where the pitfalls are. You made your point. Don't need to drag them in every answer to an unrelated question.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 30, 2017, 01:02:06 PM
...
You cannot prove they are wrong.
...

You are assuming I cannot scientifically prove they are wrong.

But if that's indeed the case, then we are back to an invisible flying spaghetti monster situation. Or see here: https://en.wikipedia.org/wiki/Russell%27s_teapot
Or here: https://en.wikipedia.org/wiki/The_Demon-Haunted_World#Dragon_in_the_garage

The burden of proof is on Ding et al, not on me or others who think like me that the demise of Arctic sea ice is 100% due to AGW.

Check points 4 to 8 of jai mitchell's first post in this thread (post #15). Michael E. Mann has expressed serious doubts about the validity of the attribution conclusion in the Ding et al 2017 paper.

BTW, that none of the 11 co-authors accepted to answer questions on a public forum about their paper says a lot to me. While I agree that the comments section of a blog such as Stoat is not an ideal forum, here on ASIF or on RC I would imagine it would generate an interesting and informative thread.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 30, 2017, 01:37:25 PM
Fair, I fell in the same trap... I am assuming....  but with the same logic is the burden of the proof on climate scientists to prove they are right when the denialati spew their nonsense?
We cannot have it both ways...

all they did was do some calculations based on some hypothesis and convinced themselves they are right. They might or might not... somebody else will come and prove them wrong... that is how science works...  if there is a flaw in the setup of simulations will be proven by somebody repeating those calculations in a different way not by public debate. Especially since they did not make a prediction that can be observed or not. They compared A vs B where they thought that B has not anthropogenic influence. That cannot be experimentally observed ... we do not have an alternative Earth. Past climates also had their own trajectories and state variable values that are different than today.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 30, 2017, 03:07:00 PM
Fair, I fell in the same trap... I am assuming....  but with the same logic is the burden of the proof on climate scientists to prove they are right when the denialati spew their nonsense?
We cannot have it both ways...
In the specific case of the Ding et al 2017 paper, the burden of proof lies on the 11 co-authors because they come up with a new (and some would say ad-hoc) hypothesis to explain why existing sea ice models that rely on anthropogenic forcing do not match the observed Arctic sea ice decline. Instead of simply stating that existing sea ice models do not capture all the mechanisms by which anthropogenic forcing affects Arctic sea ice, and trying to improve those models (cf my various references to the Sea Ice Model Intercomparison Project - SIMIP), they hypothesize that it is "natural climate variability" that has affected atmospheric circulation that in turn is causing "30~50%" of the observed rapid decline in Arctic sea ice.
Replacing "natural climate variability" by "Invisible Flying Spaghetti Monster" or "the dragon in my garage" changes practically nothing in their argumentation, because we don't have the data for the Arctic before 1979, so it's impossible to scientifically prove them wrong with hard physical evidence or historical records.

This is what Neven wrote in reply#1 in this thread:
Quote
"... no one has said that all of Arctic sea ice loss is 100% caused by AGW*. It might be, but we can't know for sure. It might even be more than 100% if natural variation would otherwise have caused the ice to grow. We don't know."

So it's really the case that nobody can prove Ding et al 2017 are wrong, but we can argue that it is most likely that they are wrong: that's the argument that one-sided "natural variability" for 40 years straight is highly unlikely. Or that we are still waiting and will probably still be waiting by the end of the century for "natural variability" to flip around and bring back the September Arctic sea ice (which will be gone for good in less than 10 years from now).

As to your question "... is the burden of the proof on climate scientists to prove they are right when the denialati spew their nonsense?", the simple answer is no. Because there is a ton of reliable, irrefutable and crystal clear evidence about AGW.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Tor Bejnar on March 30, 2017, 06:34:18 PM
...
Keeping it simple: there are no "tipping points" for a simple chunk of ice, however large it may be such as the Barnes ice cap: it's not a complex system, there are no positive feedbacks, and it melts linearly to the amount of energy/heat you apply to it.
It isn't a "simple chunk of ice". (My bias is geology.)  It has glaciers coming off of it (source of ice loss) and it snows (source of ice gain), among other influences. 

According to the Canadian Glacier Inventory Project (http://cgip.wikifoundry.com/page/Barnes+Ice+Cap):
Quote
...
Many studies have shown that recession has been taking place for centuries, especially in the south and west, but the recession has not been uniform along the margin
...
All research suggests that should continued warming take place, shrinking of the Barnes Ice Cap will accelerate
...
The Ice Cap’s configuration was reached approximately 5000 years B.P., and further evidences indicate some parts of the ice cap had readvanced just 100 years ago
 ...
Field studies in the early 1950s found that all of the Ice Cap’s winter accumulation is usually melted in the summer, and the Ice Cap is maintained close to equilibrium through the formation of superimposed ice (Bell and Jacob, 1997). [superimposed ice = frozen melted snow]
...

30-some years ago I was led to believe that AGW might cause so much more high-latitude winter precipitation that Arctic glaciers would expand.  It turns out that it does snow more, but that this extra snow is almost always more than offset by increasing melt.

In Washington, glaciers formed on Mount St. Helens (https://en.wikipedia.org/wiki/Crater_Glacier) after she blew her top.  Under the right conditions, glaciers can still thrive.  (But it'll continue to get rarer and rarer.)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on March 31, 2017, 05:12:12 AM
There have been some developments in my discussion with the authors of Ding et al 2017 regarding the issues with the method used in their paper.

Here is my most recent post on William Connolley's "stoat" site :

http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58653 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58653)

---

After Qinghua posted his findings that the adjusted forcing for experiment 6 still had a trend (in post 61; thank you Qinghua) I decided respectfully take the conversation private (polite email with the authors).

Yet now Eric Steig decided to take his opinion about me and the process of expressing scientific criticism on his paper in this fine blog public in a rather unprofessional rant of 9 twitter posts :
https://twitter.com/ericsteig (https://twitter.com/ericsteig)

Now, since Eric decided to take the discussion public again, why not take the scientific discussion public again also :

The main problem with Ding et al 2017 is that the regression method they used for experiment 6 :

B(x, y, t) = β(x, y) × Z200 GL (t) (1)

eliminates ANY trend in ANY of the variables, regardless of if these trends are "anthropogenic" or "natural variability" in nature.
And thus they can no longer claim to attribute any part to "natural variability" alone.

Their method essentially makes the climate constant during JJA in experiment 6. When confronted about that (by me in post 58).
Qinghua presented a graph (in post 61) which still has a (35%) residual trend.

The problem is that this graph represents the annual average climate used in experiment 6, and decidedly NOT the summertime (JJA) average, which shows no trend.
The residual 35% trend is the contribution from the other 9 months, where they let the climate follow the original ERA data (which still shows an uptrend since 1979).

We KNOW that Qinghua's graph does not show JJA climate in experiment 6, since when I asked Eric to look at that data he replied (on twitter) that he had to "re-do a bunch of calculations" to obtain that data :
https://twitter.com/ericsteig/status/847494244524736517 (https://twitter.com/ericsteig/status/847494244524736517)

The flaw in Ding et al 2017 is there for everyone to see, if you just follow the science.
I'm disappointed that instead of embracing the criticism and engaging in a technical discussion, Eric Steig instead resorted to an argument of authority on twitter.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on March 31, 2017, 05:39:43 AM
There have been some developments in my discussion with the authors of Ding et al 2017 regarding the issues with the method used in their paper.

Here is my most recent post on William Connolley's "stoat" site :

http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58653 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58653)

---

After Qinghua posted his findings that the adjusted forcing for experiment 6 still had a trend (in post 61; thank you Qinghua) I decided respectfully take the conversation private (polite email with the authors).

Yet now Eric Steig decided to take his opinion about me and the process of expressing scientific criticism on his paper in this fine blog public in a rather unprofessional rant of 9 twitter posts :
https://twitter.com/ericsteig (https://twitter.com/ericsteig)

Now, since Eric decided to take the discussion public again, why not take the scientific discussion public again also :

The main problem with Ding et al 2017 is that the regression method they used for experiment 6 :

B(x, y, t) = β(x, y) × Z200 GL (t) (1)

eliminates ANY trend in ANY of the variables, regardless of if these trends are "anthropogenic" or "natural variability" in nature.
And thus they can no longer claim to attribute any part to "natural variability" alone.

Their method essentially makes the climate constant during JJA in experiment 6. When confronted about that (by me in post 58).
Qinghua presented a graph (in post 61) which still has a (35%) residual trend.

The problem is that this graph represents the annual average climate used in experiment 6, and decidedly NOT the summertime (JJA) average, which shows no trend.
The residual 35% trend is the contribution from the other 9 months, where they let the climate follow the original ERA data (which still shows an uptrend since 1979).

We KNOW that Qinghua's graph does not show JJA climate in experiment 6, since when I asked Eric to look at that data he replied (on twitter) that he had to "re-do a bunch of calculations" to obtain that data :
https://twitter.com/ericsteig/status/847494244524736517 (https://twitter.com/ericsteig/status/847494244524736517)

The flaw in Ding et al 2017 is there for everyone to see, if you just follow the science.
I'm disappointed that instead of embracing the criticism and engaging in a technical discussion, Eric Steig instead resorted to an argument of authority on twitter.

Whoever relies on Twitter to whine like that is an arrogant prick...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 31, 2017, 12:50:10 PM
...

Their method essentially makes the climate constant during JJA in experiment 6. When confronted about that (by me in post 58).
Qinghua presented a graph (in post 61) which still has a (35%) residual trend.

The problem is that this graph represents the annual average climate used in experiment 6, and decidedly NOT the summertime (JJA) average, which shows no trend.
The residual 35% trend is the contribution from the other 9 months, where they let the climate follow the original ERA data (which still shows an uptrend since 1979).

...
(emphasis mine)
Rob, we don't have access to the graph that you mention.

From Qinghua post #61 on Stoat:
Quote from: Qinghua Ding
...
Actually, we did all these calculations before we implemented Exp. 6. The test shows we still have 35% of trend retained after that Z200-GL influence is removed. I have sent a figure to Rob.
...
(emphasis mine)
Please, could you share that graph which apparently Qinghua Ding sent to you by email with the rest of us here?

As for Eric Steig's Twitter rant, well, I disapprove. It seems both Steig and Qinghua Ding are running away from a technical discussion. If 2017 Ding et al are so sure they made no mistake, why not seize this opportunity to completely clarify this matter, cross all the t's and dot all the i's?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 31, 2017, 01:00:44 PM
Yet now Eric Steig decided to take his opinion about me and the process of expressing scientific criticism on his paper in this fine blog public in a rather unprofessional rant of 9 twitter posts

I tweeted Eric again:

https://twitter.com/jim_hunt/status/847764942665248768

I wonder if I'll get a reply this time?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 31, 2017, 01:17:51 PM
Yes, that Twitter rant is painful, especially when someone says that online discussions aren't productive. On the other hand, Steig had a very nasty experience many years ago when Iago McIntyre came after him (for some paper on Antarctic warming). But Rob Dekker isn't a climate risk denier and he's not responsible for other people implying malice.

Anyway, that Stoat thread is a mess now.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on March 31, 2017, 03:16:20 PM
Steig had a very nasty experience many years ago when Iago McIntyre came after him

Speaking of which, and only marginally off topic!

https://twitter.com/jim_hunt/status/847696552046993409 (https://twitter.com/jim_hunt/status/847696552046993409)

See also:

http://GreatWhiteCon.info/2017/03/the-house-science-climate-model-show-trial/#Mar-31 (http://GreatWhiteCon.info/2017/03/the-house-science-climate-model-show-trial/#Mar-31)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Steven on March 31, 2017, 03:26:06 PM
The main problem with Ding et al 2017 is that the regression method they used for experiment 6 :

B(x, y, t) = β(x, y) × Z200 GL (t) (1)

eliminates ANY trend in ANY of the variables, regardless of if these trends are "anthropogenic" or "natural variability" in nature.
And thus they can no longer claim to attribute any part to "natural variability" alone.

Their method essentially makes the climate constant during JJA in experiment 6. When confronted about that (by me in post 58).
Qinghua presented a graph (in post 61) which still has a (35%) residual trend.

The problem is that this graph represents the annual average climate used in experiment 6, and decidedly NOT the summertime (JJA) average, which shows no trend.
The residual 35% trend is the contribution from the other 9 months, where they let the climate follow the original ERA data (which still shows an uptrend since 1979).

You're confused.  I'm pretty sure that Qinghua Ding's comments on the Stoat blog are correct.

I opened Figure 1c of the Ding et al. 2017 paper with some graphics software (GIMP), and estimated the coordinates of all the data points in the black and purple curves in that Figure:  http://i.imgur.com/QeDGIMR.png. (http://i.imgur.com/QeDGIMR.png.) 

Next, I inserted those numbers in a spreadsheet, and I performed the linear regression that Ding et al. used in their paper.

According to my calculation, about 33% of the trend of downwelling longwave radiation (LW) during summer (JJA) remains after the regression.  That is very close to the 35% number that Ding mentioned.  My calculation gives an original trend of about 2.08 W/m2/decade,  and after the regression it's about 0.68 W/m2/decade:  http://i.imgur.com/FhyMYog.png. (http://i.imgur.com/FhyMYog.png.)
 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on March 31, 2017, 04:57:06 PM
Quote
I think I made it very clear in my plot and email to rob that the curve is for jja only .
It is Not annual mean. it doesn’t include any non summer month. It is June-July-august.
The regression we used can only partially remove the signals in jja since correlations between the z200 index with those jja variables are around 0.7 to 0.8. Please see our fig 1 .
There is still 30to 40% stuff left in exp6 that includes both residual trends and year to year changes.

Rob D. -- at what point do you give this up?  You have been told in no uncertain terms that the regression is for JJA and that 35% of the trend remains.  All you have done so far is continually assert that the authors are incorrect.  That the regression is for annual, that all trend is removed.

This means A.) the authors don't understand regression.  They don't understand the variables they're working with.  They can't understand it *even* when pointed out to them.

Or B.)   *you* are mistaken.

This has gone beyond silly.


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on March 31, 2017, 05:09:47 PM
The main problem with Ding et al 2017 is that the regression method they used for experiment 6 :

B(x, y, t) = β(x, y) × Z200 GL (t) (1)

eliminates ANY trend in ANY of the variables, regardless of if these trends are "anthropogenic" or "natural variability" in nature.
And thus they can no longer claim to attribute any part to "natural variability" alone.

Their method essentially makes the climate constant during JJA in experiment 6. When confronted about that (by me in post 58).
Qinghua presented a graph (in post 61) which still has a (35%) residual trend.

The problem is that this graph represents the annual average climate used in experiment 6, and decidedly NOT the summertime (JJA) average, which shows no trend.
The residual 35% trend is the contribution from the other 9 months, where they let the climate follow the original ERA data (which still shows an uptrend since 1979).

You're confused.  I'm pretty sure that Qinghua Ding's comments on the Stoat blog are correct.

I opened Figure 1c of the Ding et al. 2017 paper with some graphics software (GIMP), and estimated the coordinates of all the data points in the black and purple curves in that Figure:  http://i.imgur.com/QeDGIMR.png. (http://i.imgur.com/QeDGIMR.png.) 

Next, I inserted those numbers in a spreadsheet, and I performed the linear regression that Ding et al. used in their paper.

According to my calculation, about 33% of the trend of downwelling longwave radiation (LW) during summer (JJA) remains after the regression.  That is very close to the 35% number that Ding mentioned.  My calculation gives an original trend of about 2.08 W/m2/decade,  and after the regression it's about 0.68 W/m2/decade:  http://i.imgur.com/FhyMYog.png. (http://i.imgur.com/FhyMYog.png.)
 

Steven,
Thank you for your effort in making these two charts, one "reverse-engineered" and the second computed by you. If any of the 11 co-authors had the data I am sure it would have taken just a few minutes of their time to post them as well as the spreadsheet data, and settle the matter - if only it were that simple.
There were a couple of follow-up posts by Rob and Qinghua Ding on Stoat that make the matter more confusing, but they are very interesting.
Quote from: Rob Dekker
Qinghua.
Thank you for your reply.
If you used simple linear regression, then your method will eliminate any trend in the JJA record.
The graph you showed still shows a 35% residual trend, which suggest it is NOT the JJA climate for experiment 6.
After all, where would that residual 35% trend come from ?

Unfortunately Qinghua Ding pulls a "but the dragon in my garage is invisible" as a response, while implicitly admitting to the mistake Rob has pointed since the beginning.

Quote from: Qinghua Ding
the residual trend could be due to Co2 or cloudiness changes that are not related to the Z200 index.
the Z200 index has a strong interdecadal jump around 2003-2005. In our 2014 paper, we have argued that this interdecadal jump is not totally due to the Co2 rise.
So our regression can only remove this interdecadal like jump in the forcing fields. Some slowing increasing trends, as those due to Co2 forcing, cannot be removed by this regression.

At this stage, this could go on forever, because the dragon (in this case the cause of the 35% residual trend) can be made weightless, odorless, etc, etc, etc.

(see https://en.wikipedia.org/wiki/The_Demon-Haunted_World#Dragon_in_the_garage and https://en.wikipedia.org/wiki/Ad_hoc_hypothesis)

To me, this last exchange between Rob and Qinghua Ding is absolutely illuminating.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on March 31, 2017, 05:35:10 PM
Maybe Rob Dekker and Steven can work this out further now, because if Ding and Steig are right, this is a waste of their time.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on March 31, 2017, 06:50:08 PM
This just published yesterday.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL073138/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2017GL073138/abstract)

North Pacific 20th century decadal-scale variability is unique for the past 342 years
Williams et al. (2017)

Abstract

Reconstructed sea surface temperatures (SSTs) derived from Mg/Ca measurements in nine encrusting coralline algal skeletons from the Aleutian archipelago in the northernmost Pacific Ocean reveal an overall increase in SST from 1665 to 2007. In the Aleutian SST reconstruction, decadal-scale variability is a transient feature present during the 1700s and early 1800s and then fully emerging post-1950. SSTs vary coherently with available instrument records of cyclone variance and vacillate in and out of coherence with multi-centennial Pacific Northwest drought reconstructions as a response to SST-driven alterations of storm tracks reaching North America. These results indicate that an influence of decadal-scale variability on the North Pacific storm tracks only became apparent during the mid-20th century. Furthermore, what has been assumed as natural variability in the North Pacific, based on 20th century instrumental data, is not consistent with the long-term natural variability evident in reconstructed SSTs pre-dating the anthropogenic influence.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Darvince on March 31, 2017, 07:14:46 PM
That seems nearly too well timed to have been random chance. ;D

Although, I did read several PDO papers several months ago and they all seemed to point towards the cycle speeding up around 1850, coincidentally (or not?) when human CO2 emissions began to have an effect on the biosphere. The flips between negative and positive won't have any sum detrimental effect on the sea ice, as the loss during negative phases may be more rapid (and PDO, was mostly negative from 1998 to 2013, and flipped since then, with losses slowing during the positive phase. During the negative phase trapped heat is stored in the oceans, accelerating SLR, while during the positive phase the trapped heat is released into the atmosphere. The flip was to such a strong positive mode that I doubt that it will return to being strongly negative next year.

http://research.jisao.washington.edu/pdo/ (http://research.jisao.washington.edu/pdo/)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 31, 2017, 07:28:04 PM
Thanks jai mitchell.

Without considering the technical details and just by reading the abstract of the Williams et al paper,  the conclusions of Ding et al are compatible with Williams et al but only if Ding et al attributes the changes in tropospheric currents to variations of pacific sst's, not natural variation. In a different world that would be a trivial technicality, but if the proper political context is acknowledged, it is a very important distinction.

That said thanks to Rob Dekker, steven, Ding and Steig and everyone trying to get the best possible truth out of this. I have learned a lot.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on March 31, 2017, 07:39:07 PM
That seems nearly too well timed to have been random chance. ;D


  ;D I thought the same thing, but is so convenient that I had to take it. I would love to see the whole paper.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Steven on March 31, 2017, 09:21:13 PM
Maybe Rob Dekker and Steven can work this out further now, because if Ding and Steig are right, this is a waste of their time.

Neven, I think it's clear that Ding and Steig are right about this.

In case Rob Dekker wants to check my calculations in Reply #216 upthread:  below are the numbers that I used in the calculation.  As mentioned, the two middle columns were estimated from Figure 1c in Ding et al. 2017.  All those numbers are for summer (JJA).  The units for the LW numbers are W/m2, whereas the GL_Z200 numbers are expressed in meters.

Code: [Select]
year      LW     GL_Z200   LW_after_regression
1979    -1.11    -23.24     0.60
1980    -3.43      8.30    -4.00
1981    -1.77     -3.32    -1.51
1982    -4.43    -15.49    -3.28
1983    -2.99    -58.09     1.23
1984    -1.55     -1.66    -1.40
1985    -0.77    -14.38     0.29
1986    -2.21    -33.75     0.25
1987    -1.44     25.45    -3.25
1988    -0.55      1.11    -0.61
1989    -1.44    -31.54     0.86
1990     0.06     -3.32     0.32
1991    -0.06    -29.88     2.13
1992    -5.86    -86.31     0.39
1993    -1.27      5.53    -1.65
1994    -3.04    -67.50     1.85
1995     0.83      3.87     0.58
1996    -6.14    -68.05    -1.21
1997    -3.32    -13.83    -2.30
1998     1.49     38.73    -1.27
1999     0.83    -14.38     1.89
2000    -2.77    -14.94    -1.66
2001    -1.88     -9.96    -1.14
2002     1.55      8.30     0.98
2003     1.27     44.26    -1.89
2004     2.27     12.17     1.42
2005     6.20     24.90     4.43
2006     3.43     12.72     2.54
2007     6.86     54.77     2.94
2008     1.72     32.64    -0.61
2009     1.77     27.66    -0.20
2010     4.59     55.33     0.63
2011     4.98     55.33     1.01
2012     6.64     75.24     1.24
2013    -0.66    -26.00     1.24
2014     2.05     39.83    -0.80
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on March 31, 2017, 09:43:10 PM
This just published yesterday.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL073138/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2017GL073138/abstract)

North Pacific 20th century decadal-scale variability is unique for the past 342 years
Williams et al. (2017)

Abstract

Reconstructed sea surface temperatures (SSTs) derived from Mg/Ca measurements in nine encrusting coralline algal skeletons from the Aleutian archipelago in the northernmost Pacific Ocean reveal an overall increase in SST from 1665 to 2007. In the Aleutian SST reconstruction, decadal-scale variability is a transient feature present during the 1700s and early 1800s and then fully emerging post-1950. SSTs vary coherently with available instrument records of cyclone variance and vacillate in and out of coherence with multi-centennial Pacific Northwest drought reconstructions as a response to SST-driven alterations of storm tracks reaching North America. These results indicate that an influence of decadal-scale variability on the North Pacific storm tracks only became apparent during the mid-20th century. Furthermore, what has been assumed as natural variability in the North Pacific, based on 20th century instrumental data, is not consistent with the long-term natural variability evident in reconstructed SSTs pre-dating the anthropogenic influence.

This makes more sense to me than the whole of what I have read before in this thread.  I will read about it -- and continue to ignore the GCM intercomparisons.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 01, 2017, 02:48:32 AM
Steven, thank you so much for the idea to use fig1c for the data !
I duplicated your results (I get 30-35% residual trend for both LW and temperature).

I went a step too far, and made a mistake.
I made my apology to Qinghua and Eric on the 'stoat' site :

http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58681 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58681)
---
Thanks to 'Steven' at the ASIF, I realized that I don't need to do a full ERA data download and a gridded regression analysis to test how much of the trend in summertime temperature and LW is taken out by Z200 changes if we apply the Ding et al 2017 regression method.

We can get a pretty good estimate by using the data from fig1c and run the numbers.
I did that today, and indeed it shows (just like Qinghua already told me) a 35% residual trend for LW. Temperature shows a similar (35%) residual trend.

So, even though I find it difficult to accept that 65% of the trend in summertime Arctic temperatures would be caused by 'atmospheric circulation' (natural variability), leaving only 35% for AGW, I do understand the mistake I make and I (humbly) apologize to Qinghua and Eric for my arrogant stand on the issue.
---

I'm going to be very quiet for a while now.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 01, 2017, 03:35:10 AM
Rob Dekker  I lack the necessary technical knowledge to challenge the technical merits of the paper, so I accept the paper as technically correct. Your challenge of the paper gives me even more confidence that the technical aspects of the paper are correct. Thank you.

 I still challenge the assertion that the seemingly random variability of an atmospheric current is equivalent to natural variability.
 
 In fact, I think that this result is really bad news. The way I see it what Ding et al proved was that the atmosphere has gained enough "momentum" due to AGW, that it now overshadows CO2 induced warming as the primary driver of arctic sea ice loss.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: epiphyte on April 01, 2017, 06:26:07 AM
Rob Dekker  I lack the necessary technical knowledge to challenge the technical merits of the paper, so I accept the paper as technically correct. Your challenge of the paper gives me even more confidence that the technical aspects of the paper are correct. Thank you.

 I still challenge the assertion that the seemingly random variability of an atmospheric current is equivalent to natural variability.
 
 In fact, I think that this result is really bad news. The way I see it what Ding et al proved was that the atmosphere has gained enough "momentum" due to AGW, that it now overshadows CO2 induced warming as the primary driver of arctic sea ice loss.

Kind of like hitting the curb too hard when parking? Once you knock it out of balance the steering shakes, and if you ignore it for long enough then eventually the lugs shear and the wheel falls off.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: epiphyte on April 01, 2017, 07:21:24 AM
Randy,

The majority of the scientists and engineers do not have the skills to be concise,  on target and quick on come backs. It is unfortunate...

Yesterday I asked one of my kids (a west-coast engineering major home for spring break) to proofread a draft of the white paper I'm writing to illustrate the value offered by a technology startup of which I'm a co-founder. He said something to the effect of :

"Dad, this is good... but most people can hold fewer than five things in working memory. If you make an argument which requires more than three, you're pitching on the wrong end of the bell curve."

 - out of the mouths of babes...

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 01, 2017, 09:33:51 AM
...
The way I see it what Ding et al proved was that the atmosphere has gained enough "momentum" due to AGW, that it now overshadows CO2 induced warming as the primary driver of arctic sea ice loss.
Hi Archimid,
Sorry, but I don't think they proved that at all, and not even their conclusion states that.

I just re-read this entire thread here on ASIF, then the comments section on Stoat. I still feel the Ding et al 2017 article (and by extension the Ding et al 2014 article) deserves a public debate about the assumptions, methodology, and conclusion, but with the willing participation of Ding, Steig and other co-authors.

Dragging unwilling scientists into a discussion on a comments section of a blog is a useless exercise, and the worst way to get any real debate going.

Meanwhile...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 01, 2017, 10:06:39 AM
Quote
I just re-read this entire thread here on ASIF, then the comments section on Stoat. I still feel the Ding et al 2017 article (and by extension the Ding et al 2014 article) deserves a public debate about the assumptions, methodology, and conclusion, but with the willing participation of Ding, Steig and other co-authors.

How about sitting it out and letting the peer-review process do its thing? If Ding et al. is flawed, it will show up in the data. It will still have been useful as a pointer in the right direction.

Rob Dekker, I commend you for trying to get to the bottom of things and admitting you've made a mistake. All I could do, was scan the paper for typos (found two).

If it weren't for people implying malice, I think the scientists wouldn't have been bothered by this at all.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Peter Ellis on April 01, 2017, 11:36:19 AM
Yesterday I asked one of my kids (a west-coast engineering major home for spring break) to proofread a draft of the white paper I'm writing to illustrate the value offered by a technology startup of which I'm a co-founder. He said something to the effect of :

"Dad, this is good... but most people can hold fewer than five things in working memory. If you make an argument which requires more than three, you're pitching on the wrong end of the bell curve."

 - out of the mouths of babes...

That is a fabulous explanation, and I am henceforward going to use it to train all my PhD students and postdocs in grant writing. Please thank your son for me!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 01, 2017, 12:51:57 PM
Hi Archimid,
Sorry, but I don't think they proved that at all, and not even their conclusion states that.

Hi AndrewB,
They don't reach that conclusion because they conflate natural variability with anthropogenicaly altered random variability.  In a way the math is right, but the interpretation of it is wrong.

Quote
Dragging unwilling scientists into a discussion on a comments section of a blog is a useless exercise, and the worst way to get any real debate going.

It is not a useless exercise. It is just that the results of this exercise gets lost in the noise. But if only a few people gained a better understanding of models, the scientific process, the climate or variability the discussion was not useless.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 01, 2017, 01:04:12 PM
...
they conflate natural variability with anthropogenicaly altered random variability.
...

No, I don't think they conflate anything such, whatever you may mean by "anthropogenicaly altered random variability".  ??? (I'll politely decline your explanation of what you mean by that)

Quote from: Archimid
Quote from: AndrewB
Dragging unwilling scientists into a discussion on a comments section of a blog is a useless exercise, and the worst way to get any real debate going.

It is not a useless exercise.

I guess we'll have to agree to disagree on that too.  ;D
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: GeoffBeacon on April 01, 2017, 02:19:28 PM
AndrewB

I'd quite like to know what Archimid meant by "anthropogenicaly altered random variability".
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 01, 2017, 02:30:39 PM

No, I don't think they conflate anything such, whatever you may mean by "anthropogenicaly altered random variability".  ??? (I'll politely decline your explanation of what you mean by that)

I like epiphyte's analogy:

"Kind of like hitting the curb too hard when parking? Once you knock it out of balance the steering shakes, and if you ignore it for long enough then eventually the lugs shear and the wheel falls off."

The physical attributes of the wheel and the car dictate the way the wheel should spin. Small forcings from wear and tear caused by regular use and misuse slightly alter the way the wheel should spin. Over time these "forcings" increase in magnitude. At some point a tipping point is reached and the wheel falls off.


In this analogy a brand new car with intact suspension system dictate the natural variability of the wheels. Use and misuse of the car is antropogenic forcings. In this analogy Ding et al measures the variability of the wheel of an old car and claims the variations in wobbles and angles of the wheel is the intended natural variability of the car. But it is not. The variation he is measuring has already changed due to use and misuse.







Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 01, 2017, 02:38:17 PM
AndrewB

I'd quite like to know what Archimid meant by "anthropogenicaly altered random variability".

A fair six sided dice has a natural variability. If you change the weight of one of the sides of the dice it will still have random variability but it will be a different variability. The variability of the weighted dice is "anthropogenicaly altered random variability"
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: gerontocrat on April 01, 2017, 02:54:15 PM
Given the sheer amount of additional heat absorbed and accumulated in the oceans over the last n years (where n is a largish number) due to AGW, is anything that happens in the oceans and the atmosphere purely a result of natural variation ? I think I am just supporting the anthropogenetically altered random variability suggestion, which certainly struck a chord with me.

And I don't just mean effects on arctic sea ice or ENSO etc. I mean just about anything that is happening in / to the biosphere.

 
AFTERTHOUGHT: It ain't called "The Anthropocene" for nothing, is it.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 01, 2017, 06:28:58 PM
AndrewB

I'd quite like to know what Archimid meant by "anthropogenicaly altered random variability".

A fair six sided dice has a natural variability. If you change the weight of one of the sides of the dice it will still have random variability but it will be a different variability. The variability of the weighted dice is "anthropogenicaly altered random variability"

Archimid,
Actually if the dice is weighted the bias will quickly show, and you can mathematically separate it from the inherent randomness of the dice. In climate science where you have essentially "noisy" data, you can extract a "signal" of anthropogenic warming by various techniques (and in some cases by simply plotting a trend line), same as you can extract seasonality effects, leaving just the "natural climate variability". The expression "anthropogenicaly altered random variability" is not used. I now see that what you mean by that expression is the sum of natural variability + anthropogenic forcing signal.

Let me give you an example using Arctic sea ice extent in September.

In the chart below, you can choose a trendline, and you can see that the actual measured sea ice extent is randomly above and below the trendline.

What the Ding et al paper 2017 claims is that you can actually extract the trendline and then split the trend into two parts: 50-70% being anthropogenic forcing and 30-50% being "natural climate variability", or what they attribute to random long-term changes in atmospheric circulation. They make that claim based on how the models they used behave when the trend in GL-Z200 is removed from the data fed to the models, which they then notice have noticeably less ice loss, etc, etc, etc.

They also separate the anthropogenic signal from the noisy data in GL-Z200. Accordingly, they determine that changes in atmospheric circulation are mostly due to "natural climate variability" and in a smaller part due to anthropogenic forcing.

So your objection is indeed covered in the 2017 paper by Ding et al.

If there is anything you don't think I have made myself clear about in the above, don't hesitate to ask.

 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 01, 2017, 06:34:21 PM
Given the sheer amount of additional heat absorbed and accumulated in the oceans over the last n years (where n is a largish number) due to AGW, is anything that happens in the oceans and the atmosphere purely a result of natural variation ?
...

No, nothing that happens these days in the oceans or the atmosphere is purely the result of natural climate variability, and nothing is purely the result of anthropogenic forcing. You use mathematical techniques to extract the anthropogenic forcing signal from the data. Extracting a "natural climate variability" signal from the data in much harder, because how do you extract an inherently random signal from noisy data? Mathematically, it's impossible.

This is why the Ding et al paper goes in a sort of convoluted reasoning about this: they run their model first with the the complete data, and then they remove what they claim is the "natural climate variability" signal (the trend in GL-Z200) from the data and assume what happens in the following model run is the anthropogenic forcing. See the objection to this by Michael E. Mann which I have already mentioned in one of my comments above.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: epiphyte on April 01, 2017, 08:30:03 PM
Yesterday I asked one of my kids (a west-coast engineering major home for spring break) to proofread a draft of the white paper I'm writing to illustrate the value offered by a technology startup of which I'm a co-founder. He said something to the effect of :

"Dad, this is good... but most people can hold fewer than five things in working memory. If you make an argument which requires more than three, you're pitching on the wrong end of the bell curve."

 - out of the mouths of babes...

That is a fabulous explanation, and I am henceforward going to use it to train all my PhD students and postdocs in grant writing. Please thank your son for me!

I'll do that :)   

... I'm chagrined to admit that it's close to the top of my own "Things I wish I'd Known 20 Years Ago" list!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 01, 2017, 08:58:06 PM
Yesterday I asked one of my kids (a west-coast engineering major home for spring break) to proofread a draft of the white paper I'm writing to illustrate the value offered by a technology startup of which I'm a co-founder. He said something to the effect of :

"Dad, this is good... but most people can hold fewer than five things in working memory. If you make an argument which requires more than three, you're pitching on the wrong end of the bell curve."

 - out of the mouths of babes...

That is a fabulous explanation, and I am henceforward going to use it to train all my PhD students and postdocs in grant writing. Please thank your son for me!

I'll do that :)   

... I'm chagrined to admit that it's close to the top of my own "Things I wish I'd Known 20 Years Ago" list!

Absolutely!  That was a jem..
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 01, 2017, 10:30:24 PM
Just for the record Ding's reply to Rob Dekker's apology:
http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58682 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58682)

“Hi Rob,
I really appreciate that you said that. I also learned something from you. The paper is very condensed because we submitted it as a letter. So we couldn’t cover everything in the main text. But I think we should include more description of Exp6 in the method part given its important role in illustrating our main conclusion.

In addition, we argued in the paper that 30% of the Z200 change over Greenland could still be due to anthropogenic forcing. So combining 60% and 70% (100% minus 30%) together (60% *70%) eventually gives us that about 40% of the sea ice trend since 1979 could be owing to a natural source. As I said, this is a very condensed letter-style article, which leaves almost no room for us to discuss this natural variability in detail. I think we will do better in the future if we would publish anything on a similar topic.
.
Again I really appreciate your interests and comments on our paper.

Have a nice weekend!

Best

Qinghua

Steven, I really appreciate your help in sorting this out. Many thanks!!”
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: TerryM on April 01, 2017, 10:31:11 PM

Yesterday I asked one of my kids (a west-coast engineering major home for spring break) to proofread a draft of the white paper I'm writing to illustrate the value offered by a technology startup of which I'm a co-founder. He said something to the effect of :

"Dad, this is good... but most people can hold fewer than five things in working memory. If you make an argument which requires more than three, you're pitching on the wrong end of the bell curve."

 - out of the mouths of babes...


Perhaps I'm confused.
If the objective of your paper is to win the hearts and minds of the (below)average consumer your son is correct. But if the aim is to influence professionals charged with corporate buying who are educated in the field, and who have been selected for their intellect as well as their education and experience, won't you lose a few by dumbing down your presentation?
Depending on the product of course, I'd assume that a rifle shot, or multiple shots, would be more effective than a presentation designed to be inclusive for those on the left side of the curve.


Not meaning to rain on your parade
Terry
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 01, 2017, 10:45:49 PM
Thanks for all your interests in our paper.  I told Rob when I got his first email that I would like to discuss with anyone on stoat about our study. Since most scientific discussions about our paper have been happening on ASIF, I decide to start a discussion here. But what I will say only represents my own personal view and not that from the other 10 coauthors. I want to make this point very clear in the beginning. 

I think our paper is not a study to play with those trends/interdecadal changes or regression procedures. We actually provide a different perspective to understand the warming process in the arctic in the past three-four decades.

In the paper, we didn't only focus on temporal variability. We focused on spatial changes of the large scale circulations in the Arctic.
 
Under CO2 forcing, the ensemble mean of all IPCC models ( these are almost the best models we can use, trust and learn from) gives us a very uniform rise of Z200 everywhere in the Arctic and a much less rise in the lower levels of the troposphere (Fig. 4 of our paper).  This is because uniform CO2 warming( the greenhouse effect) will increase the depth of each atmospheric layer a little bit and thus the heights in the upper levels have the largest increase because of a cumulative effect of all small increases of layers below. So we can only see less increases of the heights in the lower levels but higher increases of heights at the higher levels.   

In contrast , the observation show a very different structure with the most significant rise of geopotential height over Greenland at all levels from the surface to the upper troposphere.  we call this type of change as a barotropic structure change.
 
I think my understanding of this difference is that the observed circulation pattern is a classical heat wave pattern that favors maximum warming in the lower boundary to melt sea ice and the build-up of the heat wave pattern over the Arctic in the past decades is due to some low-frequency variability of atmospheric Rossby wave originated from the tropics.

In other words, the wind changes due to some remote forcing  in the past 30to 40 years pushed more air masses into the Arctic and then air there became more condensed and warmed. I think this is an important dynamical factor that caused so fast sea ice melting in the past decades.   

It is still under debate whether this remote tropical forcing is internal or forced by the CO2 rise. What I learned from those IPCC models is that the observed tropical forcing pattern since 1979, especially in the recent decade is not the pattern favored by CO2 forcing. Please see our 2014 paper on this tropical linkage.

please see here about heat wave
http://scijinks.gov/heat/ (http://scijinks.gov/heat/)

or here on wiki page: the formation part

 https://en.wikipedia.org/wiki/Heat_wave (https://en.wikipedia.org/wiki/Heat_wave)

however, the temperature warming pattern/structure favored by anthropogenic forcing in JJA in the Arctic is uniform everywhere with weaker intensity in the boundary layer. That is why, ( my personal view), most iPCC models cannot reproduce so fast sea melting as that observed if the models are only forced by Co2 forcing. 

An analogy of this comparison is that anthropogenic forcing on the Arctic can be looked as turning on a furnace to warm a room. Internal forcing looks like putting a heated blanket on someone who feels cold. So this blanket ( as extra warming in the boundary layer in the real world) warms the guy faster.

In this paper, we just tried to use a model approach to remove this blanket and see how the room temperature increase melts sea ice. We also realized that some heating from the heated blanket to ice may also be due to the room temperature increase. In our attempt to do a final attribution analysis, we further removed that part and eventually got to that 40% contribution.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 01, 2017, 11:14:43 PM
Welcome to the ASIF, Qinghua, and thanks for dropping by to further explain the paper.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 01, 2017, 11:50:00 PM
Quote
In contrast , the observation show a very different structure with the most significant rise of geopotential height over Greenland at all levels from the surface to the upper troposphere.  we call this type of change as a barotropic structure change.
 
I think my understanding of this difference is that the observed circulation pattern is a classical heat wave pattern that favors maximum warming in the lower boundary to melt sea ice and the build-up of the heat wave pattern over the Arctic in the past decades is due to some low-frequency variability of atmospheric Rossby wave originated from the tropics.

In other words, the wind changes due to some remote forcing  in the past 30to 40 years pushed more air masses into the Arctic and then air there became more condensed and warmed. I think this is an important dynamical factor that caused so fast sea ice melting in the past decades.
This was noted by some commenters on the Arctic Sea Ice Blog back in 2011 and 2012 (the Forum didn't exist yet), notably by bloggers like Wayne Davisdon and Chris Reynolds. I wrote a blog post about it called Signs of Arctic climate change (http://neven1.typepad.com/blog/2012/09/signs-of-arctic-climate-change.html). I believe Wayne posited that it had to do with the Cold Pole shifting to Greenland because the sea ice-covered Arctic Ocean no longer got cold enough to keep the Cold Pole there.

In a discussion on this Cold Pole (http://forum.arctic-sea-ice.net/index.php?topic=186.0) here on the Forum in 2013, Chris Reynolds wrote (http://forum.arctic-sea-ice.net/index.php/topic,186.msg4398.html#msg4398):

Quote
I have some sympathy with Wayne's cold pole idea. However the geopotential height well still centres clearly on the Arctic ocean, and I still see this as an important problem with Wayne's view. I need to explain.

(...)

Now the centre of action of the new summer circulation is over Greenland. From the GPH plot it can be seen that there is a ridge of GPH over Greenland. There always has been a ridge, but it is now about 50m higher than typical heights pre 2007. But it is clear that from the point of view of GPH the centre of action remains over the ice pack, not over Greenland. The Jetstream flows around the GPH well.

This GPH ridge is the cause of the new summer pattern, what causes the ridge is not known with certainty, it may be due to Eurasian snow retreat, but there may be a role for Arctic sea ice loss and formation of low pressure over the Siberian coast. I suspect that once the ridge is formed it creates connections with a region around it (3000km distant) via atmospheric waves which drive the formation of a belt of low pressure tendency in response to the Greenland GPH ridge.
And over on the Blog, a year earlier, he wrote (http://neven1.typepad.com/blog/2012/09/arctic-ice-melt-20-years-of-co2-emissions.html?cid=6a0133f03a1e37970b017c31b73cd8970b#comment-6a0133f03a1e37970b017c31b73cd8970b):

Quote
This high pressure anomaly over Greenland is actually the result of a GPH ridge extending northwards from the mid latitudes, Due to the dominant wavenumber of the rossby waves, wavelength and speed, they set up a semi permanent standing wave that creates this ridge over Greenland.

This is exactly what Dr Francis was talking about in her paper on patterns in the jet stream getting stuck! The relevant pattern of the jetstream is even printed in one of the figures.

And I didn't think to connect the two patterns.

Stupid!
But to get back to Qinghua's quote. It's an interesting idea that "the wind changes due to some remote forcing  in the past 30to 40 years pushed more air masses into the Arctic and then air there became more condensed and warmed. I think this is an important dynamical factor that caused so fast sea ice melting in the past decades".

That brings me to the question I have had since first reading about the paper: Let's say most of the natural variability has to do with wind changes pushing more air masses into the Arctic. Do we have any way of knowing when this natural variability might switch again and thus slow down the current rapid rate of Arctic sea ice loss? Or is that now a new research route?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: P-maker on April 02, 2017, 12:18:08 AM
Dear Quinghua

Nice to see you pop out of the blue just like that.

Since Neven and I seem to be the only ones awake at this time of night, I will also have a go at your thoughts.

Concerning “anthropogenic forcing in JJA” , I have previously argued on the Forum ( see http://neven1.typepad.com/blog/2014/05/piomas-may-2014.html?cid=6a0133f03a1e37970b01a73dc49f69970d#comment-6a0133f03a1e37970b01a73dc49f69970d (http://neven1.typepad.com/blog/2014/05/piomas-may-2014.html?cid=6a0133f03a1e37970b01a73dc49f69970d#comment-6a0133f03a1e37970b01a73dc49f69970d) )  that a large increase in Tropical cyclone activity in 2004-6 could have contributed to the advection of hot, dry air aloft, which could have reached Greenland and caused the observed jump in Z200 around that time.

Concerning your idea of “putting a heated blanket on someone who feels cold. So this blanket ( as extra warming in the boundary layer in the real world) warms the guy faster.” It is actually not what happens in real life. If the temperature of a body has become too low for the heart to beat properly and pump blood around in the body, it will not warm the guy faster, if you put a heated blanket (e.g. as snow cover in the real world) on the poor guy. It will actually isolate his cold body from the heat in the room! If the Arctic sea ice is genuinely cold, as it was before 2005 roughly speaking, it was almost impossible to get rid of the multi-year sea ice, no matter how hard you tried to heat it.

The heat waves identified by you in the reanalysis may only be visible over Greenland due to the fact that very few upper air balloons are launched regularly outside Greenland these days. Previously, a number of observational platforms were in use (e.g. ice islands, submarines, ice-breakers and research stations etc.) in the Arctic. The decline in Arctic upper-air observations is a serious threat – even though we tend to think that Reanalysis nowadays come close to the real thing.

Cheers P


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 02, 2017, 12:25:38 AM
Hi Neven,
To be honest, I don't know the answer.
In my view, The easiest way to check our finding is to examine a long free run of a fully coupled model ( that includes air-ocean-sea ice)  without CO2 forcing. There are plenty of these runs available in our community. I am sure the heat wave circulation pattern would be the key player in these runs to melt sea ice in JJA.
 
We have got some very positive results on this direction and I am working on a paper with Axel and Eric so I don't want to say too much about it. I hope you can understand it.
Through understanding this internal sea ice melting mode, which is similar to what we have observed in the real world, in a long free run, we would know better about its periodicity, evolutions and oceanic or atmospheric preconditions of turning points, etc.
   
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 02, 2017, 12:40:24 AM
Hi P-maker ,
Thanks for your comment. I will read the thread you referred to.
I agree reanalysis is not perfect to reflect what is really happening over the Arctic ocean. But I also checked satellite temperature data ( I think it is RSS or UAH or something else) . It is very consistent with reanalysis over the ocean showing a temperature warming trend in the troposphere. I will show you a plot if you are interested to take a look. Actually, I think all these satellite informations have been assimilated into reanalyses.
Best
Qinghua 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 02, 2017, 04:04:09 AM
Dr. Qinghua,

First I would like to thank you warmly for accepting to participate in a discussion of your Arctic sea ice 2017 paper here on ASIF, which I believe is a much better venue than the comments section on the Stoat blog.

Personally I have two burning questions for you. The first is a scientific question, the second is in the moral/philosophical domain. Here they are:

1. In the abstract of your 2017 paper, one can read: "Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30-50% of the overall decline in September sea ice since 1979." My question (in two parts) is: how confident are you and your co-authors about these numbers, and what scientific experiment could be made, or physical evidence would be required, if any, to invalidate this claim?

2. 2017 just saw the lowest maximum Arctic sea ice extent on record (NSIDC), 2016 was the third hottest year on record in a row and 1.1C above pre-industrial (WMO), and atmospheric CO2 concentration has passed the 405ppm threshold, 125ppm above pre-industrial and probably the highest it has been in over 1 million years according to ice core data (Keeling curve). And 25% of the world's corals died in 2016, as a result of ocean warming.
As a climate scientist and seeing we as human beings are on a path to a global climate disaster, do you feel any sense of responsibility or moral conflict when authoring a paper that clearly weakens the scientific, economic and political case for the urgent adoption of radical emissions reductions policies, to avoid the worst effects of global warming / climate change / ocean acidification?

Thank you again for willingly joining this discussion here on ASIF.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: GeoffBeacon on April 02, 2017, 05:49:49 AM
Welcome Dr. Qinghua,

Quote
the build-up of the heat wave pattern over the Arctic in the past decades is due to some low-frequency variability of atmospheric Rossby wave originated from the tropics.


I remember asking one climate scientist what he thought about Jennifer Francis' claims that a warmer Arctic slows down the jet stream and creates meridional jet stream flow, changing the pattern of Rossby waves. I asked if changes in weather patterns were due to such an effect?

At that time, he said it wasn't certain whether the changes were best explained this way. The alternative explanation was the the Pacific Decadal Oscillation.

Dr Francis' describes a change driven by anthropogenic greenhouse gas emissions but the PDO is internal variability.

Do you have a view on Dr Francis' work?

Is a Francis/PDO dichotomy still reasonable?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 02, 2017, 11:39:18 AM
Quote
As a climate scientist and seeing we as human beings are on a path to a global climate disaster, do you feel any sense of responsibility or moral conflict when authoring a paper that clearly weakens the scientific, economic and political case for the urgent adoption of radical emissions reductions policies, to avoid the worst effects of global warming / climate change / ocean acidification?

This again feeds into the myth that mainstream scientific opinion has been that 100% of Arctic sea ice loss was due to anthropogenic causes, and that now suddenly this paper puts a spanner in the work. This is what climate risk deniers use for their spin.

But it isn't true. The question has always been how much of a role natural variability plays in the rapid decline we have seen over the past 30 years. There are numerous papers on the influence of the PDO, the AMO, etc. This is just one more such paper.

The paper doesn't 'clearly weaken the scientific, economic and political case for the urgent adoption of radical emissions reductions policies' in itself. It's the spin that does that.

I don't know what can be done wrt science communication to prevent this kind of spin. Does that mean that Ding and his co-authors shouldn't pursue what they deem interesting, constructive science? I'd say no.

But this is an entirely different discussion and I'd rather we'd take it elsewhere, and use this thread to focus on the science in the paper.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 02, 2017, 11:57:47 AM
@ Qinghua

"Under CO2 forcing, the ensemble mean of all IPCC models ( these are almost the best models we can use, trust and learn from) gives us a very uniform rise of Z200 everywhere in the Arctic and a much less rise in the lower levels of the troposphere (Fig. 4 of our paper).  "

y, i have look your used models as shown in the Supplementary. It turns out, that the mean of model you used have to much ice, to strong aplitude and a to low sea ice trend. On the other Hand, z200 is strong correlate with SIC (Sea-Ice-Concentration) in Models, since the Models you used have a less trend then observed, its no wonder, that increase of z200 is less. Also the pattern, you cant rule out, that this pattern would not exist if Models would loose ice the same as in Observation.

Anyway, as also shown on stoat, if you pick the best model to the parameters Annual Extent, Trend and Amplitude ( MPI-ESM-MR*) its nearly perfect reproduce the observed SIC-Minimum (September)

http://www.directupload.net/file/d/4674/5kode2k9_png.htm (http://www.directupload.net/file/d/4674/5kode2k9_png.htm)

See also here:
http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58603 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58603)
http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58580 (http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/#comment-58580)

*via climate-explorer RCP2.6


In other Words, if you say, the models show the forced response mainly due GHGs, this would imply, that the discrepance trend and pattern in z200 can also be just a result of unrealistic arctic sea ice states in Models.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 02, 2017, 11:59:53 AM
Dear dr Ding,

Thank you for replying here at the ASIF.
What I'm wondering about after reading your paper is how it relates to the work of Maslowski et al 2014:
http://www.iopan.gda.pl/profima/Strona%20RO/chapter_5.pdf (http://www.iopan.gda.pl/profima/Strona%20RO/chapter_5.pdf)

They say:
“Based on our model results and limited observations, we found that heat content of the Western Arctic ocean in the top 120 m has been increasing since the late 1990s and appears to be contributing to the rapid sea ice decline there. Our model analysis implies that the advection of warm water from Bering Strait regulates the retreat of sea ice and contributes to the relatively high surface air-sea fluxes over the Chukchi shelf. Earlier ice melt in the Chukchi Sea allows increased absorption of solar radiation and warming of water over the shelf, before it is exported into the Beaufort Sea where it can further contribute to sea ice melt. Based on evidence from observations and from our model, we argue that not all the heat content in the western Arctic Ocean gets removed back to the atmosphere every year before freezing in fall and early winter. We hypothesize that instead the remaining heat above the halocline and below the mixed layer acts to reduce sea ice growth in winter and preconditions an earlier ice melt each year, which further increases heat content in the region, thus resulting in a positive feedback accelerating summer reduction of the sea ice cover. The presence and spreading of a subsurface heat source in the western Arctic Ocean and the large-scale sea ice drift of the Beaufort Gyre help explain why the sea ice has continued to decline most dramatically in that part of the Arctic Ocean, even when large-scale atmospheric conditions were not always most favorable to such a decline (i.e. when the Arctic Oscillation Index was neutral or extremely negative).”

Earlier Maslowski et al 2012 had said:
http://www.oc.nps.edu/NAME/Maslowski%20et%20al.%202012%20EPS%20Future%20of%20Arctic%20Sea%20Ice.pdf (http://www.oc.nps.edu/NAME/Maslowski%20et%20al.%202012%20EPS%20Future%20of%20Arctic%20Sea%20Ice.pdf)

“a system-level understanding of critical Arctic processes and feedbacks is still lacking. To better understand the past and present states and estimate future trajectories of Arctic sea ice and climate, we argue that it is critical to advance hierarchical regional climate modeling and coordinate it with the design of an integrated Arctic observing system to constrain models…

There are many Arctic climatic processes that are omitted from, or poorly represented in, most current-generation GCMs. These processes include the following: oceanic eddies, tides, fronts, buoyancy-driven coastal and boundary currents, cold halocline, dense water plumes and convection, double diffusion, surface/bottom mixed layer, sea ice–thickness distribution, concentration, deformation, drift and export, fast ice, snow cover, melt ponds and surface albedo, atmospheric loading, clouds and fronts, ice sheets/caps and mountain glaciers, permafrost, river runoff, and air–sea ice–land interactions and coupling…

the development and use of high-resolution regional Arctic climate and system models and process-level subsystem models are important stepping stones in the coming decade for dedicated studies of regional processes and feedbacks, tests of new parameterizations and ensemble simulations, and the prediction of sea ice and other components of the Arctic System in a warming climate.”

And more recently Notz et al 2016 say:
http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016.pdf (http://www.geosci-model-dev.net/9/3427/2016/gmd-9-3427-2016.pdf)

“it is sobering to see to which degree simulations of its past and future evolution differ across large-scale coupled models (e.g. Massonnet et al., 2012; Stroeve et al., 2012), how much retrieved sea-ice properties from one satellite product differ from another satellite product (e.g. Meier and Notz, 2010; Ivanova et al., 2015), and in how many aspects the simulations and observations differ from each other (e.g. Massonnet et al., 2012; Stroeve et al., 2012; Turner et al., 2013; Stroeve et al., 2014; Gagné et al., 2015; Shu et al., 2015).We do not yet know how much these differences are irreducible, for example because they are due to internal variability of the climate system, and how much they reflect biases in the model’s representation of the functioning of the climate system in high latitudes. This lack of understanding hinders further improvements of our models, an identification of observational needs, and a robust assessment of the most likely future evolution of sea ice in response to the ongoing climatic changes on Earth.”

I guess this comes down to the question AndrewB asks above about how confident we can be about the model results of your recent paper. Are these models good enough yet to warrant our confidence in them, or should we be quite sceptical still until they have been substantially improved, as Maslowski et al and Notz et al seem to imply?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: epiphyte on April 02, 2017, 05:31:28 PM
@Qinghua ding - Wonderful to see you here!

And of course I have a question for you... Given that the current state of the arctic is a result of anthropogenic forcing and natural variation in exactly the proportions your paper suggests, what does that portend for the future? Do the fluctuations caused by natural variation accelerate the transition to a new regime, or rather do they retard or even prevent it?

(Needless to say, I have my own opinion on this, but it's hardly an informed one, so I'll keep it to myself for now!)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 02, 2017, 06:08:45 PM
First, thanks to Dr. Ding for writing this paper and taking the time to post here.

Thanks AndrewB for your detailed response. You are very much right when you say:

"I now see that what you mean by that expression is the sum of natural variability + anthropogenic forcing signal".


Archimid,
Actually if the dice is weighted the bias will quickly show, and you can mathematically separate it from the inherent randomness of the dice. In climate science where you have essentially "noisy" data, you can extract a "signal" of anthropogenic warming by various techniques (and in some cases by simply plotting a trend line), same as you can extract seasonality effects, leaving just the "natural climate variability".

I understand that is what they did. I think they removed any known variation relevant to their experiment and the remaining noise they call "natural variation" for the 1979-2014 time period. I think they would have been right in call it random variation or climate variability, noise or any other word that didn't imply lack of human interference.

But when they call the noise "natural variation" they imply that the noise is free of human interference. Given the shortness of the experiment and given knowledge of how sensitive sst's are to human forcings and given current events(which are outside their experiment), I find it very highly unlikely that the noise has no anthropogenic signature. Specially if they refer to AGW as just CO2 warming. If they disregard other anthropogenic forcings like aerosols and deforestation, or if they disregard feedback effects of CO2 forcing like albedo changes and changes in the hydrologic cycle, all of which have temporal and spatial effects on natural variability, then the use of "natural variability" becomes even worse.

My argument is that their semantics are wrong, not their methods. I admit, the semantic may seem trivial because calling the noise "natural variation" may be correctly interpreted by many scientist as just noise. So calling the noise "natural variation" may be very convenient. But in a politically charged, life and death argument like the climate change argument, utmost precision is required.

 When they say that atmospheric currents may be up to 60% responsible for Arctic sea ice reduction I agree with them because it makes sense. But if they say natural variation  may be up to 60% responsible for Arctic sea ice reduction that flies in the face with everything else I know. Climatologically speaking, pure natural variation dictates that the earth should be well underway to the next ice age. According to the most pure signal of natural variation, Arctic sea ice should be growing. Instead we are seeing a flash melt (in climatological terms).


I fear that I may be speaking over you and others and that is certainly not my intention. I hope I made my point more clear.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on April 02, 2017, 06:22:02 PM
I still do not see how you can purport to distinguish signal from noise using models with no proven skill.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Pettit on April 02, 2017, 07:01:04 PM
I still do not see how you can purport to distinguish signal from noise using models with no proven skill.

There are a lot of people here; to which "you" are you referring?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on April 02, 2017, 07:09:42 PM
I still do not see how you can purport to distinguish signal from noise using models with no proven skill.

There are a lot of people here; to which "you" are you referring?

Well...since it is the skill of the GCM I question that would have to be anyone who attempts to use the GCM to make a point.

We now have weather models that work just fine for about ten days before failing badly.  I've seen no evidence at all that the GCM can even do 10 days -- and I've seen quite a bit of evidence they cannot do one year.

<JP: This thread is about a particular published paper that discusses spatial changes in large scale Arctic circulations, and their effect on things such as ice coverage, etc. It's not the place to rehash and reteach the difference between weather and climate, and why comparisons between short-term weather forecasts and long-term climate predictions aren't particularly valid. (See more here if you're interested (https://www.skepticalscience.com/weather-forecasts-vs-climate-models-predictions-intermediate.htm))>

<Jim W., I'll let this one go through, but it's really WUWT-level. I would kindly ask others to not react to this; N.>
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 02, 2017, 08:24:44 PM
Dr. Ding,

the 2003-2005 increase in Chinese high-temperature aerosols has been identified as a driver in the negative PDO during that decade.  These were confirmed by CMIP5.

However, the CMIP5 does not include the suppression of lapse rate feedbacks from upper troposphere aerosols.  Secondary cloud effects of SO2 aerosols are also not well modeled.

Many studies have shown that these aerosols also work much more intensely in providing cooling in the arctic, with some estimates that over 50% of GHG forcing could be offset by these aerosols.  Leading to a nearly instant jump of temperatures by 1.8C (edit note: regionally in the arctic not globally averaged)

In view of the rapid changes in atmospheric circulation/translation from the tropics both from the East Pacific Warm Pool and the Gulf of Mexico this last winter, and the observation that China has significantly reduced their aerosol emissions from high-temperature industrial processes, it is very clear that the current models do not accurately capture these impacts.

with the paleoclimate analysis of the early Pliocene period where we had similar CO2 levels showing a north Canadian equable climate regime.  It is clear that these SO2 emissions have prevented a shift into a climate regime much more in line with the early Pliocene period that the one we have been studying for the last 50 years.  A bifurcated state of the global climate, one that is not captured by the CMIP5 ensembles.

I assert that, in the total absence of aerosol emissions and at 560 CO2e GHG abundance, we will see an arctic ice free condition during the Summer Solstice.  I also assert that we will continue to see rapid changes in atmospheric circulation, far above the modeled predictions, and that we will see an effective ice free state in the arctic in the next 6 years (Sept. minimum).

This means that we have already surpassed the threshold for 2.3 C, that rapid feedbacks will destabilize the boreal forest, the amazonian tropical forest and the boreal permafrost, at rates far greater than the decomposition that we are already noting are far and above the predictions of CMIP5.  These feedbacks and others (ocean acidification impacts on Dimethyl Sulfide production), Arctic ocean albedo shifts from algae blooms, reduction in far-infrared emissivity from open ocean in the Arctic) will produce additional warming, in the absence of anthropogenic activity that will lock-in >3.2C of warming at current GHG abundance levels (and in the absence of aerosols).

And yet our best scientists still talk as though we may avoid +1.5C of warming, that we still have a carbon budget left and that the Summer arctic sea ice will likely be maintained through 2060.  Axel has stated this to me very recently and unequivocally.

So how are we supposed to take a body of scientists who speak in terms that fit a prescribed narrative, are technically constrained by 'common knowledge' assumptions and even terminologies like 'natural variability' that are assigned to things like atmospheric circulation patterns that have a definitive anthropogenic fingerprint?

Especially in the view that anthropogenic aerosols have significantly reduced the rate of sea ice loss over the last 4 decades, and in their absence the expected loss would far exceed the 30%-60% 'natural variability' that your paper attributes to Z200 GPH tropical translations.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 02, 2017, 09:06:29 PM
Lots of questions. I'm sure everyone understands if Qinghua is too busy to answer.  :)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 02, 2017, 10:50:37 PM
Many thanks for all your interesting/burning/critical/constructive comments and questions on our paper and my thoughts.

The first thing I want to say is that no one should expect that our short paper could fully address the most challenging question we are facing now in the polar community.

I am 100% sure that the mechanism of that "polar heat wave idea" is correct, since this is the only way ( in my personal view) to explain everything ( "everything" here means changes in sea ice, winds, temperature, vertical velocity and radiation fields) that we have observed in the Arctic  since 1979.  If we only considered CO2 forcing, it always puzzled me that some observed features in the Arctic cannot be well supported by either model results or dynamics of the Co2 greenhouse effect. But I have to say that we didn't consider aerosol in our work.

That 40% contribution from natural forcing is what we concluded based on the facts of our modeling experiments and a IPCC/NCAR model evaluation task.

In the paper, we used three steps of experiment/evaluation to reach to this number.

A. the first set of experiments

model: ECHAM5 with a simple ocean/sea ice:

purpose:
to determine the direction of causality of observed connections between the circulation and all other variables.

conclusion:
1. the experiments qualitatively prove that the observed circulation change is important to regulate all other variables 
2. and these atmospheric changes in JJA cannot be explained by sea ice melting if we only put Arctic sea ice decline in the model

B. IPCC/NCAR models evaluation 
purpose: to consider whether forced responses of models to CO2 forcing can explain some observed features and understand how much the observed circulation change is still forced by CO2 forcing

Conclusion: we found that CO2 forcing cannot reproduce some features in the observation and only a part of the circulation change in the arctic is due to CO2 . 

C. the third set of experiments:

model: a more sophisticated sea ice and ocean model ( a part of CESM) without atmosphere.
purpose: quantify how much of sea ice melting is due to the circulation change
conclusion: circulation related forcing at the interface between sea ice and atmosphere can substantially melt sea ice

This is our strategy to tackle the problem. I think this is not the perfect one but the best one we could come up with by using available in-house tools. As I know, our study is the first one to use a numerical model to tease the influence of the circulation on sea ice apart from other influences.  So I think it is an important step forward to open up a new direction to understand arctic sea ice.

In the paper ( the first paragraph in the conclusion part) , we acknowledged this limitation.
"
 Our conclusions are based on experiments involving several models
rather than one integrated model. POP2CICE4 simulations are
used to allow for a realistic simulation of sea-ice variability, while
ECHAM5 simulations allow for realistic simulations of the linkage
between circulation and thermodynamic drivers of sea-ice loss,
while permitting nudging to observed wind fields. The close
agreement of patterns of thermodynamic forcing on sea ice between
the ECHAM5 and POP2CICE4 provides confidence in combining
these two tools."

another part in the paper to discuss a possible way to improve our understanding

"Therefore, a substantial
contribution of tropical Pacific variability on sea ice loss via this
teleconnection is to be expected. A further examination of this
question will require a modelling framework that reproduces the
tropics high latitude linkage faithfully and efficiently."

In my current work, I am working on a new project to repeat the experiments using a fully coupled model. That means combining  sets A and C together into one integrated experiment to understand how the recent wind changes influence sea ice. I am sure with this better approach, we will move closer  to the real contribution of natural forcing on sea ice melting but I still wouldn't say that I am 100% sure that the new number is correct because we never know whether another model would give the same number.


 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: seaicesailor on April 03, 2017, 12:16:31 AM
What I don't understand in all this discussion is why that presumed natural variability that shows as a GPH ridge over Greenland and all associated perturbed circulation so detrimental for the ice cannot have been caused, indirectly, by the so many changes AGW has directly caused, in the SSTs, the humidity, the glaciers, the sea ice and so on. Just what comes first to the head of a layman...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 03, 2017, 03:26:34 AM
I still do not see how you can purport to distinguish signal from noise using models with no proven skill.

Within the limits of the models, signal from noise can be mathematically distinguished. But when the real world is taken into account, the models become wrong.

Let's think of a very basic model that is right so often that most people accept it as truth. Distance = Time x Speed. That model, D=ST is wrong if enough accuracy is required. To meet that accuracy other models are incorporated like friction, acceleration, wind speed, wind direction, air composition. Once these models are added accuracy increases but only to a point. If extreme accuracy is needed then more models must be added and sometimes completely replaced to meet the need.


Climate models are no different. They have been built with sweat and toil over time to account for more and more accuracy, more and more phenomena. Will they ever be complete? I mean will they ever predict the climatic condictions with 99.99% accuracy for every location of the world for decades even centuries ahead? I think they will, just like astronomists have the movements of the universe figured out to an extreme degree and particle physicists have the small scales figured out.

Are the models there yet, no. Regrettably not. Have they shown enough skill to take action? God yes. Specially with the preponderance of evidence from virtually all sciences.



Qinghua ding:

Quote

 But I have to say that we didn't consider aerosol in our work.

...snip...

"Therefore, a substantial contribution of tropical Pacific variability on sea ice loss via this teleconnection is to be expected. A further examination of this question will require a modelling framework that reproduces the tropics high latitude linkage faithfully and efficiently."


I look forward to your next work.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: GeoffBeacon on April 03, 2017, 04:32:48 AM
Overland et.al. Nonlinear response of mid-latitude weather to the changing Arctic (http://www.nature.com/nclimate/journal/v6/n11/full/nclimate3121.html)

Abstract:
Quote
Are continuing changes in the Arctic influencing wind patterns and the occurrence of extreme weather events in northern mid-latitudes? The chaotic nature of atmospheric circulation precludes easy answers. The topic is a major science challenge, as continued Arctic temperature increases are an inevitable aspect of anthropogenic climate change. We propose a perspective that rejects simple cause-and-effect pathways and notes diagnostic challenges in interpreting atmospheric dynamics. We present a way forward based on understanding multiple processes that lead to uncertainties in Arctic and mid-latitude weather and climate linkages. We emphasize community coordination for both scientific progress and communication to a broader public.

Relevant here?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Hunt on April 03, 2017, 09:24:11 AM
Many thanks for all your interesting/burning/critical/constructive comments and questions on our paper and my thoughts.

Many thanks for taking the time and trouble to provide so much input here. I have taken the liberty of reproducing your comment (together with one of Rob's) over at:

http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#comment-221177 (http://GreatWhiteCon.info/2017/03/is-arctic-ice-loss-driven-by-natural-swings/#comment-221177)

I hope that's OK with you both? Please let me know ASAP if not!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 03, 2017, 11:27:21 AM
From 2008:

Point of No Return
Quote
A new study completed by a team of US, Norwegian and German researchers may now provide some clues. Published in the scientific journal Geophysical Research Letters in November, the study posits that a dramatic change in atmospheric circulation patterns has taken place since the beginning of the decade, with centers of high pressure in winter shifting toward the north-east. The new pattern of sudden climate change is characterized by "poleward atmospheric and oceanic heat transport," the authors write in the study, a transport which drives temperature increases in the Arctic. The discovery was made using specialized filters that allow one to follow changes to high pressure centers over time.

Behind the complex language and impenetrable calculations upon which the study is based, however, is a frightening possibility: climate change in the Arctic could already have reached the point of no return. Climate researchers have long been warning of such "tipping points," and that crossing them could mean irreversible developments for eco-systems and humanity. In the case of the Arctic, that could mean a complete disappearance of ice in the region during the summer months. Such an eventuality would then further magnify global warming, due to the fact that bright white ice reflects sunlight back into the atmosphere whereas dark colored land and ocean absorbs heat.

"In the case of Arctic Sea ice, we have already reached the point of no return," says the prominent American climate researcher James Hansen, director of the Goddard Institute for Space Studies at NASA.

Winter in the Arctic has long been determined by what researchers refer to as a "tri-polar" pattern. The interaction among the Icelandic Low, the Azores High and the subtropical high in the Pacific led to primarily east-west winds, a pattern which effectively blocked warmer air from moving northward into the Arctic region.

But since the beginning of the decade, the patterns have changed. Now, a "dipolar" (bipolar) pattern has developed in which a high pressure system over Canada and a low pressure system over Siberia have the say. The result has been that Artic winds now blow north-south, meaning that warmer air from the south has no problem making its way into the Arctic region. "It's like a short-circuit," says Rüdiger Gerdes, a scientist at the Alfred Webener Institute for Polar and Marine Research and one of the five authors of the study.

Gerdes and his co-authors fear that the changes in the Arctic could mean that a "new era of global-warming-forced climate change" has begun. The volume of greenhouse gas emissions like CO2 and methane into the Earth's atmosphere could have resulted in a permanent change in the global climate system.
link (http://www.spiegel.de/international/world/fast-forward-warming-point-of-no-return-for-the-arctic-climate-a-594461.html)


And while looking for that paper I found this:

http://onlinelibrary.wiley.com/doi/10.1029/2006GL027146/abstract (http://onlinelibrary.wiley.com/doi/10.1029/2006GL027146/abstract)


The way I read it is, greenhouse gas induced warming in the 1990s reduced sea ice thickness, which initiated changes in Arctic atmospheric circulation, bringing warm air into the Arctic, amplifying melting.

So much for 'natural' variability. 

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: crandles on April 03, 2017, 01:18:08 PM
Given the way certain people have been quoted over on Stoat, I find it distrurbing and embarrassing that those people find it ok to proceed to ask questions (and presumably think they deserve some sort of answer) without at least first giving some sort of apology. This forum has gone a long way downhill. I would like to offer my apologies to Qinghua Ding and other scientists for what they have to put up with.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Peter Ellis on April 03, 2017, 02:22:04 PM
Heartily seconded, crandles.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 03, 2017, 02:28:19 PM
I agree with the apology, but I think it's also good that scientists try to understand where it comes from and don't take it personally.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 03, 2017, 02:50:32 PM
I dont think so, because for making constructive critics there should not be a apology, only if someone is making claims about the person which is always not constructive. Its also okay for the Autors, which are able to see, how their Paper make an impact to the public and get some thougths about what could cause missunderstandings from the Paper.

So, because you indirect speaking here of me, i never aks about a answer to my question, its enough if he reads what i had asked. To make my standing clear, i dont claim there is a error in the Paper, i only want to tell, that there driven conclusion (about nat. Variability) is not highly confident, because their choosen Models(in the Paper) show to much (in Hindcast) Extent, to strong Extent-Aplitude and a to low Extent-Trend, if you choose the best model to this parameter, the decrease in ice(after 2005) is nearly like observed, so if the Autors of the Paper claim, that the mean of the models would represent the forced response (mainly GHG) and the rest is more like nat. Variability, the claim would be weak, because its depends on the model which are used, since Models have a to weak decrease in sea-ice, its not clear that the models z200 (also the Pattern) would not produce nearly the same pattern of z200 if they are allowed to decrease ice the same much as in observation.

In other words:
The Model which is nearly the observed Parameters (Annual-Extent, Extent-Aplitute and Trend) in Hindcast 1979-2005, also have no problem to decrease strong as in observation since 2005...

So my Question for you is: Why should i apologie for this?

Given the way certain people have been quoted over on Stoat, I find it distrurbing and embarrassing that those people find it ok to proceed to ask questions (and presumably think they deserve some sort of answer) without at least first giving some sort of apology. This forum has gone a long way downhill. I would like to offer my apologies to Qinghua Ding and other scientists for what they have to put up with.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 03, 2017, 03:07:07 PM
I agree with the apology, but I think it's also good that scientists try to understand where it comes from and don't take it personally.

Exactly...

It also comes with the territory of public engagement.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: crandles on April 03, 2017, 05:54:22 PM

So my Question for you is: Why should i apologie for this?

Constructive criticism is great, no problem with that.

Ideally, it is possible to phrase constructive criticism or a question with appropriate respect where it is due. Phrasing as a question rather than stating as a clear certainty may help. For example: Perhaps I am missing something, but doesn't X imply Y?

The parts quoted on Stoat (see comment 107), are not constructive criticism, more like deliberate denigration. I don't have any problem with you or anyone else asking a question or providing constructive criticism. Deliberate disrespectful denigration is another matter.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 03, 2017, 06:09:53 PM
Given the way certain people have been quoted over on Stoat, I find it distrurbing and embarrassing that those people find it ok to proceed to ask questions (and presumably think they deserve some sort of answer) without at least first giving some sort of apology. This forum has gone a long way downhill. I would like to offer my apologies to Qinghua Ding and other scientists for what they have to put up with.
Since I am one of those "certain people" that were quoted on the Stoat blog by a commenter who goes by the name of Kevin O'Neill there and I suspect is ktonine here on ASIF, I will just state for the record that I don't feel my phrase that ktonine/Kevin O'Neill cross posted requires an apology, and I certainly do not intend to apologize for it.
Here is the phrase that was quoted:
Quote
"And Rob, since you asked this question “I wonder what the authors were thinking when they drew their conclusions(?)”, my answer is that they already had the preposterous claim that the disappearance of sea ice is mostly due to natural variability in mind, and just found the models and performed the simulations (which they call “experiments”) that would somehow justify their a priori conclusion."
If you read the Ding et al 2014 paper, then read the Ding et al 2017 paper, it is quite obvious that both papers use a similar methodology, rely on similar or identical assumptions (for example, that geopotential height is representative of atmospheric circulation changes), and reach a similar if not identical conclusion: the attribution of up to 50% of the observed warming or up to 50% of observed Arctic sea ice decline, to "natural climate variability".

ktonine then misconstrued my phrase into an accusation of "rigging the results" or malfeasance or whatever went through his mind at the time. Perhaps then it is ktonine who should apologize for this, and not me? :P
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Sterks on April 03, 2017, 06:30:50 PM
Andrew, now that you insist, to insinuate of having preposterous claims and using tools that justify priori conclusions sound like some of the worst insults you can throw to a scientist or to anyone doing or pretending to do an investigative work with rigor.
I mean, isn't it obvious?
But yeah, don't apologize, you're behind, hidden in your desk, safe, Eric S. has shown really ugly arrogance too.
Dr. Ding and Rob Dekker keeping the level so high in contrast. Chapeau
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 03, 2017, 06:37:21 PM

Constructive criticism is great, no problem with that.

Hope so :-)


Ideally, it is possible to phrase constructive criticism or a question with appropriate respect where it is due. Phrasing as a question rather than stating as a clear certainty may help. For example: Perhaps I am missing something, but doesn't X imply Y?

I agree, but on online discussion we often forgott this, because we are in a distance of a face to face discussion. I therefore i think ist pretty normal..

The parts quoted on Stoat (see comment 107), are not constructive criticism, more like deliberate denigration. I don't have any problem with you or anyone else asking a question or providing constructive criticism. Deliberate disrespectful denigration is another matter.

We both on the same side, such comments as you referred, are always to ignor, its just a loos of lifetime..

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 03, 2017, 06:45:37 PM
As far as apologies go, there are only two options for characterization of this paper.  the first is CYA as described below:

Quote
an attempt to shift blame of the failure of the models that radically underestimated current (and rapidly growing) climate impacts with much earlier than projected tipping point feedback engagements, an attempt to "Cover Your Ass" (CYA).

or the second, caveat to the first, as quoted below

http://forum.arctic-sea-ice.net/index.php/topic,1920.msg106582.html#msg106582 (http://forum.arctic-sea-ice.net/index.php/topic,1920.msg106582.html#msg106582)

Quote
I guess you are right Neven, it is impossible to say if this is a CYA paper from entrenched arctic scientists who have dedicated their lives to learning and teaching about these things or if their unsubstantiated interpretations of global atmospheric circulations being 'natural' even though recent studies indicate a significant anthropogenic component (due to many feedbacks, ENSO impacts and aerosol impacts) are rather based on institutional thinking, bias toward confidence in their previous work (models), failure on the SLD (Side of Least Drama) and trying to find a reason an explanation why their models are so pathetically, horribly, dis-servingly off base.

In any event, I assert that, once the arctic melts out (and I have said very clearly that I expect this to happen in the next 2 to 6 years) I can guarantee you that we will hear this paper referenced by those who want to do little or nothing in the way of climate mitigation (as we already are).

I would also like to restate that:

http://forum.arctic-sea-ice.net/index.php/topic,1920.msg106582.html#msg106582 (http://forum.arctic-sea-ice.net/index.php/topic,1920.msg106582.html#msg106582)
Quote
I can guarantee you that this physical reality and the consequences of China shutting down its 30 most sulfur producing coal mines and installing scrubbers is NOT considered in their model as anthropogenic but is rather attributed to 'natural variability'.

quote below: not only are powerful dynamics NOT included in the models, the spacial resolution of the models and impacts on atmospheric circulation are not competent enough to accurately project the impacts that ARE included due to regional scale impacts on atmospheric circulation

Quote
Results from general circulation models show almost no
changes in the relative humidity in a changing climate (Held
and Soden, 2000; Soden et al., 2005). However, very few
general circulation models have so far begun to include the
effects of aerosols on deep convective clouds (Boucher et
al., 2013; Khain et al., 2015). Namely, as noted by Khain
et al. (2015), the only feasible option in current general circulation
models is to use bulk microphysics parameterisation
schemes. However, bulk microphysics schemes have trouble
producing the effects of aerosols on cloud cover and cloud
top height. As a result, the effect of aerosols on UTH is
not correctly included in the current projections of climate
change produced by general circulation models. Estimates
of climate sensitivity that combine temperature observations
with estimates of greenhouse gas and aerosol-induced radiative
forcing should also be reconsidered.

Note: as Dr. Ding stated these effects were not looked at by the paper since the rapid reduction of high-temp SO2 emissions were not included (not in the study period).

However, the flip-side of not including the rapid RAMP UP of these emissions (2003-2006) were also not included, AND their impacts are poorly represented in the GCM models shown.  Only very recently these components were identified as primary anthropogenic contributors to the 'natural variability' that is identified in the study.

---------------
frankly, I find the idea of apologies reprehensible. 

This is why:

If I am right, if we do achieve a summer ice free condition in the next 2-6 years, if, in the absence of aerosol emissions we have already locked in +2.3C with much more rapid warming in the arctic, leading to wide-scale boreal forest conflagration and massive permafrost destabilization far ahead of the models, then we have already locked in a 2100 globally averaged temperature of a~3.5C (and a 2200 temp of greater than +8C).

It is time to leave our egos behind and get to work, if we want to prevent >+4.0C and the total global destabilization of our interdependent modern economic system.

It is time to quit talking and acting like we are not.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: GeoffBeacon on April 03, 2017, 07:04:20 PM
Just found this from Francis and Vavrus in 2015

Quote
New metrics and evidence are presented that support a linkage between rapid Arctic warming, relative to Northern hemisphere mid-latitudes, and more frequent high-amplitude (wavy) jet-stream configurations that favor persistent weather patterns. We find robust relationships among seasonal and regional patterns of weaker poleward thickness gradients, weaker zonal upper-level winds, and a more meridional flow direction. These results suggest that as the Arctic continues to warm faster than elsewhere in response to rising greenhouse-gas concentrations, the frequency of extreme weather events caused by persistent jet-stream patterns will increase.

Link (http://iopscience.iop.org/article/10.1088/1748-9326/10/1/014005)

Does an increase in "extreme weather events caused by persistent jet-stream patterns" account for any of the "natural variability" of Ding et.al. ?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 03, 2017, 07:07:44 PM
... using tools that justify priori conclusions... sound like some of the worst insults you can throw to a scientist...

First, that's not what I wrote, and second, the standard procedure is for scientists to use whatever instruments can result in the best quality data available, so that they can be confident of whatever conclusion that can be drawn from the data.

And it's pretty obvious that Ding et al, for example, used an atmospheric circulation model (ECHAM) to examine atmospheric circulation changes in the period they considered (1979-2014): they say so themselves in the paper!

Check my posts again, I was criticizing the choice of models and the fact that the skill of the models used by Ding et al is not quantified. That is a valid criticism of their methodology and not intended as an insult whatsoever.

It is also the reason I asked Dr. Qinghua my question no. 1: how confident are the co-authors about the "natural climate variability" attribution numbers (30%-50%)?

By the way, also about the methodology: if the model you are using presents, let's say, a 25% uncertainty, and you run the model twice with different data and them subtract one result from the other (Exp6 - Exp5) in the Ding et al 2017 paper, you end up with a number with 50% uncertainty. Do you see the methodological problem or not?

I'll pass on the "hidden behind your desk" and other nonsense in your post, just as I ignored most of ktonine's/Kevin O'Neill posts that just misrepresent what I wrote.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: sidd on April 03, 2017, 08:00:18 PM
I agree that some here owe the authors of the subject paper an apology. Mr Dekker has already done so, and that reflects well on him. Not so for others.

I see that many have strong feelings about the paper. I suggest they write up their objections and submit them for publication.

I suspect, however, that no apologies will be forthcoming, and, nor will a publication. But if they do, I shall be pleasantly surprised.

sidd
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 03, 2017, 08:05:20 PM
early mortality projections, mainly in sub-sahara Africa  and SE Asia under a >2.0C warming scenario are in excess of 1 billion human beings.

think about that for a minute.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 03, 2017, 08:10:06 PM
Okay, enough about the apologies. Let's keep it to the science from now on, and if we have all said everything there is to say, we can always come back to this thread if some new papers or theories wrt natural variation vs human influence pop up.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 03, 2017, 08:17:55 PM
Here is a link to the paper referred to in my previous post.

 Recent radical shifts of atmospheric circulations and rapid changes in Arctic climate system (http://onlinelibrary.wiley.com/doi/10.1029/2008GL035607/full)


And a more recent paper on the Arctic Dipole:

The recent shift in early summer Arctic atmospheric circulation (http://shoni2.princeton.edu/ftp/lyo/journals/Overland-etal-ShiftArcticSummerAtmosCirc-GRL2012.pdf)


And the sensitivity to the location of regional ice loss:

The Impact of Regional Arctic Sea Ice Loss on Atmospheric Circulation and the NAO (http://journals.ametsoc.org/doi/10.1175/JCLI-D-15-0315.1)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 03, 2017, 08:57:26 PM
AndrewB

Quote
And it's pretty obvious that Ding et al, for example, used an atmospheric circulation model (ECHAM) to examine atmospheric circulation changes in the period they considered (1979-2014): they say so themselves in the paper!

Really? As refered in the Supplementary: http://www.nature.com/nclimate/journal/vaop/ncurrent/extref/nclimate3241-s1.pdf (http://www.nature.com/nclimate/journal/vaop/ncurrent/extref/nclimate3241-s1.pdf)

Quote
Supplementary Table 1:26 climate models in the CMIP5 historical experiment.Listof 26 CMIP5 CGCMs used in Fig. 4 to examine the forced response of the climate system to anthropogenic and natural external forcing, along with the number of atmospheric horizontal grids.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: GeoffBeacon on April 03, 2017, 09:09:58 PM
jai
Quote
early mortality projections, mainly in sub-sahara Africa  and SE Asia under a >2.0C warming scenario are in excess of 1 billion human beings.
I'd be interested in a source for that.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 03, 2017, 09:19:13 PM
AndrewB

Quote
And it's pretty obvious that Ding et al, for example, used an atmospheric circulation model (ECHAM) to examine atmospheric circulation changes in the period they considered (1979-2014): they say so themselves in the paper!

Really?
...

Really really!

From the Ding et al 2017 paper (as published):

lines 46-47:
"In this paper, we examine the contribution of the atmospheric circulation to Arctic sea ice variability by utilizing an atmospheric general circulation model (ECHAM5)..."

lines 120-125:
"To better understand the direction of causality, we conduct two model experiments to examine the influence of the observed high-latitude circulation trends on sea ice and other key variables. The first experiment (Exp-1) is a 36-year historical run with the ECHAM5 atmospheric model, in which the global atmospheric circulation (vorticity and divergence from the surface to the top of the atmosphere) is weakly nudged to the corresponding daily reanalysis data (see Methods)."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 03, 2017, 09:23:24 PM
Soory, my fault, ECHAM was used for atmosphere circulation, i do have read they used it for the forced response. Thanks for reply!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 03, 2017, 09:34:30 PM
Soory, my fault, ECHAM was used for atmosphere circulation, i do have read they used it for the forced response. Thanks for reply!
No problem.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 03, 2017, 09:41:44 PM
jai
Quote
early mortality projections, mainly in sub-sahara Africa  and SE Asia under a >2.0C warming scenario are in excess of 1 billion human beings.
I'd be interested in a source for that.

http://apps.who.int/iris/bitstream/10665/134014/1/9789241507691_eng.pdf (http://apps.who.int/iris/bitstream/10665/134014/1/9789241507691_eng.pdf)

Quote
Climate change is projected to have substantial adverse impacts on future mortality, even
under optimistic scenarios of future socioeconomic development. Under a base case
socioeconomic scenario, we estimate approximately 250 000 additional deaths due to climate
change per year between 2030 and 2050.

here is the temperature range they were looking at

(https://s24.postimg.org/3reo7nzgl/figure-spm-5-l.jpg)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 03, 2017, 09:59:39 PM
And that make it quit interresting, they used (as refered in the Supplementary) 26 Models for the forced response, which i has shown, only MPI-ESM-MR is good in Hindcast the sea ice also in forecast. Then they used ECHAM5 which is the amtosphere modul of MPI-ESM-MR to examine atmospheric circulation.

Well, if you look Exp(1) of the Paper, it show, that the Pattern from ECHAM5 is looking nearly like the observation. This would imply that most of change is not independent of ice decrease(this is likly because the mean of Models fail to reproduce the Pattern and also fail to decrease as much as in Observation)

Therfore,  to examine independent atmospheric circulation impacts on trends, it should not be used the mean of this 26 Models just only the divergence to ECHAM5
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 03, 2017, 10:23:44 PM
...
Then they used ECHAM5 which is the amtosphere modul of MPI-ESM-MR to examine atmospheric circulation.
...
was, actually. ECHAM6 is the new atmospheric circulation module of the Max Planck Institute for Meteorology's MPI-ESM model.
See attached figure.

But I agree with your remark.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 03, 2017, 10:31:32 PM
Okay, enough about the apologies. Let's keep it to the science from now on, and if we have all said everything there is to say, we can always come back to this thread if some new papers or theories wrt natural variation vs human influence pop up.

Not sure this qualifies as a new paper (it's from 2016), but it certainly suggests human influence on Arctic sea ice:

Notz, D. & Stroeve, J. (2016). Observed Arctic sea-ice loss directly follows anthropogenic CO2 emission. Science, 354, 747-750 , doi:10.1126/science.aag2345

Abstract

Arctic sea ice is retreating rapidly, raising prospects of a future ice-free Arctic Ocean during summer. Because climate-model simulations of the sea-ice loss differ substantially, we used a robust linear relationship between monthly-mean September sea-ice area and cumulative carbon dioxide (CO2) emissions to infer the future evolution of Arctic summer sea ice directly from the observational record. The observed linear relationship implies a sustained loss of 3 ± 0.3 square meters of September sea-ice area per metric ton of CO2 emission. On the basis of this sensitivity, Arctic sea ice will be lost throughout September for an additional 1000 gigatons of CO2 emissions. Most models show a lower sensitivity, which is possibly linked to an underestimation of the modeled increase in incoming longwave radiation and of the modeled transient climate response.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 03, 2017, 11:03:57 PM
That paper was raked over the coals at Stoat.

http://scienceblogs.com/stoat/2016/11/06/observed-arctic-sea-ice-loss-directly-follows-anthropogenic-co2-emission/ (http://scienceblogs.com/stoat/2016/11/06/observed-arctic-sea-ice-loss-directly-follows-anthropogenic-co2-emission/)


Here is a link to the actual paper:

http://sci-hub.bz/10.1126/science.aag2345 (http://sci-hub.bz/10.1126/science.aag2345)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 04, 2017, 12:03:37 AM
...
Here is a link to the actual paper:
http://sci-hub.bz/10.1126/science.aag2345 (http://sci-hub.bz/10.1126/science.aag2345)

Thanks for the link to the PDF.

Three suggested charts to go when reading the Notz & Stroeve quite short paper (3 pages + 1 page of mostly references).

Did I mention the paper suggests 100% attribution of Arctic sea ice decline to anthropogenic forcing? Actually it pretty much contradicts the Ding et al 2017 paper, here:

"Our  results  also  suggest  that  regional  differences  in  atmospheric  heat-flux  convergence  or  wind  forcing  do  not  significantly  affect  the  Arctic-wide  mean  energy  balance  on  the  time  scales that  we  consider  here.  On  the  other  hand this  also  explains  why  the  linear  relationship  does  not  hold  in  the  Antarctic,  where  dynamical  forcing  from  wind  and oceanic heat transport are key drivers of the large-scale sea-ice evolution."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 04, 2017, 12:26:07 AM

Published online:27 March 2017

Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events
Quote
Persistent episodes of extreme weather in the Northern Hemisphere summer have been shown to be associated with the presence of high-amplitude quasi-stationary atmospheric Rossby waves within a particular wavelength range (zonal wavenumber 6–8). The underlying mechanistic relationship involves the phenomenon of quasi-resonant amplification (QRA) of synoptic-scale waves with that wavenumber range becoming trapped within an effective mid-latitude atmospheric waveguide. Recent work suggests an increase in recent decades in the occurrence of QRA-favorable conditions and associated extreme weather, possibly linked to amplified Arctic warming and thus a climate change influence. Here, we isolate a specific fingerprint in the zonal mean surface temperature profile that is associated with QRA-favorable conditions. State-of-the-art (“CMIP5”) historical climate model simulations subject to anthropogenic forcing display an increase in the projection of this fingerprint that is mirrored in multiple observational surface temperature datasets. Both the models and observations suggest this signal has only recently emerged from the background noise of natural variability.
Full Text (http://www.nature.com/articles/srep45242)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 04, 2017, 12:41:50 AM

Published online:27 March 2017

Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events
Quote
Persistent episodes of extreme weather in the Northern Hemisphere summer have been shown to be associated with the presence of high-amplitude quasi-stationary atmospheric Rossby waves within a particular wavelength range (zonal wavenumber 6–8). The underlying mechanistic relationship involves the phenomenon of quasi-resonant amplification (QRA) of synoptic-scale waves with that wavenumber range becoming trapped within an effective mid-latitude atmospheric waveguide. Recent work suggests an increase in recent decades in the occurrence of QRA-favorable conditions and associated extreme weather, possibly linked to amplified Arctic warming and thus a climate change influence. Here, we isolate a specific fingerprint in the zonal mean surface temperature profile that is associated with QRA-favorable conditions. State-of-the-art (“CMIP5”) historical climate model simulations subject to anthropogenic forcing display an increase in the projection of this fingerprint that is mirrored in multiple observational surface temperature datasets. Both the models and observations suggest this signal has only recently emerged from the background noise of natural variability.
Full Text (http://www.nature.com/articles/srep45242)

Convenient pdf
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 04, 2017, 10:21:23 AM
Thanks, StevenB for pointing to Notz & Stroeve 2016.

They say:
“during the transition to a seasonally ice-free Arctic Ocean, the 30-year running mean of monthly mean September Arctic sea-ice area is almost linearly related to cumulative anthropogenic CO2 emissions… In the model simulations, the linear relationship holds until the 30-year running mean, which we analyze to reduce internal variability, samples more and more years of a seasonally ice-free Arctic Ocean, at which point the rela-tionship levels off toward zero…

the observed linear relationship allows us to estimate a sensitivity of 3.0 ± 0.1 m2 of September Arctic sea-ice loss per ton of anthropogenic CO2 emissions during the observational period 1953–2015… the linear relationship allows for a robust evaluation of climate-model simulations. While a number of previous studies have found that the observed sea-ice retreat has been faster than projected by most climate-model simulations, it has remained unclear whether these differences are primarily a manifestation of internal variability. The sensitivity that we estimate here is, in contrast, based on the average evolution over many decades, thus eliminating internal variability to a substantial degree. A mismatch between the observed and the simulated sensitivity hence robustly indicates a shortcoming either in the model or in the external forcing fields used for a simulation…

On a more regional scale, our conceptual explanation allows us to ascribe a minor role for the overall evolution of sea ice to processes that are unrelated to the large-scale change in atmospheric forcing. This includes a minor role of oceanic heat transport on the time scales that we consider here, since we can derive a linear relationship without considering these transports. While it might alternatively be possible that the oceanic heat transports have changed monotonously in recent decades, we have no indication that this is the case from either observations or model simulations.

The current minor role of oceanic heat transports implies that on time scales of several centuries, the linearity will most likely no longer hold, since sensitivity will increase once changes in oceanic heat content start measurably affecting Arctic sea-ice coverage. Our results also suggest that regional differences in atmospheric heat-flux convergence or wind forcing do not significantly affect the Arctic-wide mean energy balance on the time scales that we consider here.”

This indeed seems to be a quite different conclusion from Ding et al. So, of course, I would be very interested to hear what Dr. Ding thinks of Notz & Stroeve 2016.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 04, 2017, 11:47:13 AM
If you are interested in the Notz & Stroeve paper but can't be bothered with reading it, there is a short YouTube video (< 5 minutes) with Dr. Notz presenting essentially the same ideas during the COP21, with various charts, etc.
Here: https://www.youtube.com/watch?v=kHXg6ucTM1o (https://www.youtube.com/watch?v=kHXg6ucTM1o)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Sterks on April 04, 2017, 02:16:31 PM

I'll pass on the "hidden behind your desk" and other nonsense in your post, just as I ignored most of ktonine's/Kevin O'Neill posts that just misrepresent what I wrote.

Ok, it was not fair from me to write that (behind my own desk), I am sorry.


If you are interested in the Notz & Stroeve paper but can't be bothered with reading it, there is a short YouTube video (< 5 minutes) with Dr. Notz presenting essentially the same ideas during the COP21, with various charts, etc.
Here: https://www.youtube.com/watch?v=kHXg6ucTM1o (https://www.youtube.com/watch?v=kHXg6ucTM1o)

The example of scientific paper that contradicts Ding et al that you bring about is not that good. I think they directly assume no internal variability. How's that for a model? They could have used something fancier. In fact, they could have used some model.
But no, it is sort of a direct ad-hoc linear correlation C02 -> ice loss only meant to work for the NH with kind of a moral intention (you burn this? then you are responsible of the loss of that amount of ice). And as a side, projecting their correlation into the future we can keep our party and our burning rates until 2040 or 2050, that the Arctic will keep some ice in September, then we stop, and fix it. It is just linear, isn't it?

Bad example really.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 04, 2017, 03:18:44 PM
Appears to be not based on a model but on past observations.

Quote
...the observed linear relationship allows us to estimate a sensitivity of 3.0 ± 0.1 m2 of September Arctic sea-ice loss per ton of anthropogenic CO2 emissions during the observational period 1953–2015.

The sensitivity that we estimate here is, in contrast, based on the average evolution over many decades...

So what they are stating is limited to past observations during the period examined.  And they say as much, merely stating that current models do not reflect past observations, but that their observations of a linear relationship will not hold under future conditions.

Fair enough.  But then they go on to project into the future based on past observations, where they already stated in essence, "past observations are not an indication of future performance".

 

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 04, 2017, 04:42:30 PM
I think they directly assume no internal variability. How's that for a model? They could have used something fancier. In fact, they could have used some model.

Notz & Stroeve start with analysing the models and find a linear relationship between cumulative CO2-emissions and Arctic sea ice extent over 30-yrs periods (running mean). Then they analyse the observations over the past six decades and also find a linear relationship, but on average almost twice as strong as in the models (which probably underestimate the negative aerosol forcing).

They say:
“Evaluating the simulated sensitivity, we find that most CMIP5 models systematically underestimate the observed sensitivity of Arctic sea ice relative to anthropogenic CO2 emissions of 3.0 ± 0.3 m2. Across the full transition range to near ice-free conditions, the multimodel mean sensitivity is only 1.75 ± 0.67 m2 loss of Arctic sea ice per metric ton of anthropogenic CO2 emissions. Because of the linear response, a similar sensitivity is obtained for subperiods of the transition period that have the same length as our observational record, with overall maximum sensitivities over such 61-year-long time periods from individual simulations of 1.95 ± 0.70 m2/ton. Note that these estimates of the models’ sensitivity might be biased somewhat high, as previous studies found that the aerosol forcing of CMIP5 simulations might have been too weak in recent decades. This would give rise to artificially amplified warming and thus amplified sea-ice loss in these simulations, rendering the true sensitivity of the models to be even lower than the values we estimate here.”

They also say:
"While a number of previous studies have found that the observed sea-ice retreat has been faster than projected by most climate-model simulations, it has remained unclear whether these differences are primarily a manifestation of internal variability. The sensitivity that we estimate here is, in contrast, based on the average evolution over many decades, thus eliminating internal variability to a substantial degree. A mismatch between the observed and the simulated sensitivity hence robustly indicates a shortcoming either in the model or in the external forcing fields used for a simulation"

So the question is how much natural variability remains after averaging over six decades? Maybe some, but probably less than by averaging over 3-4 decades as Ding et al do. So maybe the model Ding et al use is not yet fit enough for the job (assuming the observations are basically correct)?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 05, 2017, 04:41:29 AM
...
So maybe the model Ding et al use is not yet fit enough for the job (assuming the observations are basically correct)?
A climate model is a mathematical tool, you can't blame the tool for any deficiencies in a climate science paper.
Again, if the Ding et al paper had quantified the skill of the POP2+CICE4 sea ice model they used for Exp5 and Exp6, from which they derive their preposterous natural variability attribution claim, I personally would be much less critical about it.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 05, 2017, 07:48:36 AM
Again, if the Ding et al paper had quantified the skill of the POP2+CICE4 sea ice model they used for Exp5 and Exp6, from which they derive their preposterous natural variability attribution claim, I personally would be much less critical about it.

I suppose that's a better way of putting it, yes...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 05, 2017, 09:24:44 PM
Pre-publish presentation by Dr. Kim Cobb and her expanded series of ENSO variability trends over the last 7,000 years.  Her preliminary results show a much greater rate of ENSO intensity during the industrial period as compared to all pre-industrial samples.

https://www.youtube.com/watch?v=991fXJfQqms (https://www.youtube.com/watch?v=991fXJfQqms)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 07, 2017, 10:03:51 PM
Another part of the puzzle maybe, Polyakov et al 2017, Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean:
http://science.sciencemag.org/content/early/2017/04/05/science.aai8204 (http://science.sciencemag.org/content/early/2017/04/05/science.aai8204)

With coverage by Chris Mooney in Washington Post:
https://www.washingtonpost.com/news/energy-environment/wp/2017/04/06/scientists-say-the-unique-arctic-ocean-is-being-transformed-before-our-eyes/?tid=ss_tw&utm_term=.b76837f8095d (https://www.washingtonpost.com/news/energy-environment/wp/2017/04/06/scientists-say-the-unique-arctic-ocean-is-being-transformed-before-our-eyes/?tid=ss_tw&utm_term=.b76837f8095d)

Abstract
Arctic sea-ice loss is a leading indicator of climate change and can be attributed, in large part, to atmospheric forcing. Here, we show that recent ice reductions, weakening of the halocline, and shoaling of intermediate-depth Atlantic Water layer in the eastern Eurasian Basin have increased winter ventilation in the ocean interior, making this region structurally similar to that of the western Eurasian Basin. The associated enhanced release of oceanic heat has reduced winter sea-ice formation at a rate now comparable to losses from atmospheric thermodynamic forcing, thus explaining the recent reduction in sea-ice cover in the eastern Eurasian Basin. This encroaching “atlantification” of the Eurasian Basin represents an essential step toward a new Arctic climate state, with a substantially greater role for Atlantic inflows.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 11, 2017, 07:01:57 AM
I know that I've burned up much of my credibility during the recent exchange with Qinghua Ding and Eric Steig.

So I don't expect anyone to take the following notes seriously.

First of all, the subject is important.

If Arctic sea ice declines to record levels, this paper suggests that 30-50% is due to natural variability, and thus that it could revert if the "weather" changes.

However, I can't deny that I believe Ding et al 2017 still may have some serious flaws which were summarized best by Michael Mann :

https://twitter.com/MichaelEMann/status/841362467603255298
"study doesn't support that conclusion. Atmospheric circulation changes may have anthropogenic component."

Let's take this one step at a time.
Ding et al 2017 has a claim that :

Quote
Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30–50% of the overall decline in September sea ice since 1979.

This claim consists of two parts :

1) Cause :
Quote
Here, we present evidence that trends in summertime atmospheric circulation may have contributed as much as 60% to the September sea-ice extent decline since 1979.
Now, this claim is based on the Exp.5. and Exp.6. differences.
Here, Ding et al 2017 runs a model between two 'climate' regimes : One with the ERA climate data, and one with ERA data adjusted to exclude the Z200 geopotential height trend since 1979, and also adjusted 'temperature' and 'LW downwelling radiation' and 'humidity' variables, which are adjusted to the extent that Z200 changed. Their regression method causes these variables to knock out 65% of the long term trend. This all suggests that Z200 long term changes are the "cause" of the trend in temperature, humidity and LW downwelling radiation. But it may very well be that the "cause" is the long term trend in 'temperature' which may very well be (entirely or partially) anthropogenic (see Mann's note).

Which brings us to 'attribution' :

2) Attribution :
Ding et al 2017 suggests that 70% of the 60% ice loss from (1) is caused by natural forcing, leading to their final conclusion of some 40% natural cause for ice loss in the Arctic.
This (70%) is based on their experiment 7 and 8.
There, they took out the long term trend in 'high latitude wind', assuming that (30%) was anthropogenic.
However, the 'high latitude winds' may very well be caused by increase in Z200GL geopotential height increase. After all, increase in geopotential height over the Arctic leads to reduced cyclonic winds. If you assume that Z200GL increase is largely (or half, according to Ding et al 2014) caused by natural variability, then these long term changes in 'high latitude winds' that cause 30% ice loss may be caused by 'natural variability' and the remaining 70% may be caused by anthropogenic forcings.

Which turns the tables around since now 'natural variability' only causes 30% of the 60% (from point (1)) and thus only 18 % could be caused by 'natural variability', and only 9 % if half of Z200GL is caused by natural forcing.

Needless to say that there is much to argue about this paper's findings.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 11, 2017, 08:59:54 AM
Needless to say that there is much to argue about this paper's findings.

Rob, I think you're still missing the larger point; the models simply don't show transpiring what you claim.  If there's an AGW forcing for the magnitude of sea ice loss, then what is the physical flaw in the models? 

Obviously they've gone over the models dozens of times trying to figure out why they don't match observations.  At some point (Ding et al) someone was bound to come up with the rational idea that maybe it's not being entirely forced, but simply natural variation.

We always hesitate to put anything down to cycles because they're generally the first refuge of deniers like the denizens at WUWT.  But occasionally there *are* cycles that need to be taken into account.  If I recall iceberg recordss in the north Atlantic do tend to  show a 60 year cycle and this could be part of that natural variation.

Saying "it could still be AGW" without actually having any proof is really nothing more than saying I don't like the result.  It really brings to mind many peoples reaction to the Tietsche paper.  Just because Ding et al is out there doesn't for a moment mean it's accepted gospel, but better silence on the subject until something definitive is in hand to rebut it.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 11, 2017, 01:25:07 PM
I think that the forcing they choose to call natural variation is just the "momentum" accumulated in the atmosphere after 200 years of AGW. This paper is really bad news because if we could magically reduce CO2 in the atmosphere to pre industrial times in a day,  the atmosphere will probably still melt the ice for some years.

Honestly, how can they call "natural variation" from a data set that is only 37 years old? DO they expect me to believe that the natural variation over the last 37 years was the same as 200 years ago or 10,000 years ago.

No, sorry. Their use of the term natural variation is wrong for an attribution study. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Gray-Wolf on April 11, 2017, 01:35:38 PM

Honestly, how can they call "natural variation" from a data set that is only 37 years old? DO they expect me to believe that the natural variation over the last 37 years was the same as 200 years ago or 10,000 years ago.

No, sorry. Their use of the term natural variation is wrong for an attribution study.

I have to agree and the changes over the last 5 years, across the Arctic, has taken us well beyond the 'old' workings of the basin. Most every paper we read has a fat tail of data in the 'old' basin and so tends to not provide a satisfactory view of the basin that is. I have not read any 'transition' papers but surely this is where we are with a new seasonal basin in the offing and the old , myi crammed full basin, is now lost!

Though changes to the weather (WACCy impacts) are easy for us to accept we are still in 'hot debate' ,as to whether these changes are driven by low ice across the basin, in meteorology generally and so to talk of such in weather forums is still difficult if you are not ready to face abuse.....

This is not the basin that was there when I entered this life back in 63'!!!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 11, 2017, 01:49:00 PM
In their study they make the following simplification:

CO2 forcing = AGW
Everything Else = Natural variation.

In reality  AGW is much more than just CO2 forcing. For example, AGW may be the culprit behind the cold blob to the south of Greenland. I don't need to be an expert to understand that cold blob must be having effect on the atmosphere above. In the study, the changes to the sst's to the south of Greenland and their effect on the atmosphere are counted as Natural Variation, but it was CO2 induced warming that melted the ice, that changed the sst, that changed the atmosphere.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 11, 2017, 03:32:06 PM
In their study they make the following simplification:

CO2 forcing = AGW
Everything Else = Natural variation.


No, this is NOT what scientists think.  They look for patterns that emerge in the model ensembles with and without AGW (CO2) forcing and compare to observations.  Those observations that do NOT emerge with AGW forcing either indicate a flaw in the model or natural variation.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 11, 2017, 05:23:34 PM
And they failed to take into account warming oceans and warm water incursions.  They also didn't include other greenhouse gases like methane and nitrous oxide, all of it anthropogenic.

So you can stuff your natural variability.

Occam's Razor.  The IPCC climate models didn't include any of these things, so they underestimated the melting. Simple as that.

All Ding's paper did was demonstrate the IPCC models were deficient.  Duh.  Their conclusions were not satisfied by their argument.   All they could really demonstrate was that 30% of the melting was unaccounted for by CO2 forcing in the IPCC models.

But we already knew what had been left out.  Not as if the IPCC models were the core dragon of the AGW argument which they had finally slain. 

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 11, 2017, 06:43:25 PM
Effect of methane emission increases in East Asia on atmospheric circulation and ozone
Quote
Abstract

We used a fully coupled chemistry–climate model (version 3 of the Whole Atmosphere Community Climate Model, WACCM3) to investigate the effect of methane (CH4) emission increases, especially in East Asia and North America, on atmospheric temperature, circulation and ozone (O3). We show that CH4 emission increases strengthen westerly winds in the Northern Hemisphere midlatitudes, accelerate the Brewer–Dobson (BD) circulation, and cause an increase in the mass flux across the tropopause. However, the BD circulation in the tropics between 10°S and 10°N at 100 hPa weakens as CH4 emissions increase in East Asia and strengthens when CH4 emissions increase in North America. When CH4 emissions are increased by 50% in East Asia and 15% globally, the stratospheric temperature cools by up to 0.15 K, and the stratospheric O3 increases by 45 ppbv and 60 ppbv, respectively. A 50% increase of CH4 emissions in North America (with an amplitude of stratospheric O3 increases by 60 ppbv) has a greater influence on the stratospheric O3 than the same CH4 emissions increase in East Asia. CH4 emission increases in East Asia and North America reduce the concentration of tropospheric hydroxyl radicals (4% and 2%, respectively) and increase the concentration of mid-tropospheric O3 (5% and 4%, respectively) in the Northern Hemisphere midlatitudes. When CH4 emissions increase in East Asia, the increase in the tropospheric O3 concentration is largest in August. When CH4 emissions increase in North America, the increase in the O3 concentration is largest in July in the mid-troposphere, and in April in the upper troposphere.
https://link.springer.com/article/10.1007/s00376-015-5028-4


What most people don't get is it isn't just the warming.  It's also changes in atmospheric chemistry which have knock-on effects. 

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 11, 2017, 06:45:53 PM
@  Archimid @ Cid_Yama

Why you are talking Bullshit? There is nothing wrong with the paper and all what you both said is totally wrong, they used the forced response of the models, this include not just co2, its also include ch4, sox, landuse, black-carbon... they also say, that some part of unforced atmosphere pattern could be a result of feedback to the ice loose itself, but they claim more to natural impact, as i shown here, it could be also not natural (in context of most) and this is the only point for critics to the paper, or in other words, there conclusion is not so confident that the last word would be spoken about it.

So, you both making the same shit, as the denials of global warming, you are also trapped in your own world, without any kind of open mind
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 11, 2017, 06:53:01 PM
Here is a back of the envelope uncertainty analysis of the attribution claim in the 2017 Ding et al paper, for your comments.

From the abstract of the 2017 Ding et al paper: “Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30-50% of the overall decline in September sea ice since 1979.” (lines 28-29)

By “internal variability” it is assumed the authors mean “natural climate variability”, in other words, non-anthropogenic forcing.

This preposterous (i.e. against logic and common sense) claim contradicts previously published papers on Arctic sea ice decline, for example the previously mentioned 2016 Notz and Stroeve paper that evidences a linear relationship between the rise in cumulative CO2 emissions from the burning of underground fossil carbon and the decline in Arctic sea ice volume (see my previous posts).

The claim that the unprecedented decline in Arctic sea ice may be in a large part attributable to natural climate variability defies logic and common sense when we take a look at the exponential trend in Arctic sea ice volume loss evidenced by 38 years or so of satellite data. Note that not only September sea ice follows an exponential trend; all months do so, indicating that the Arctic will be essentially ice free all year round, and this probably decades before the end of the century.

As someone put it in the Stoat blog, nearly 40 years of one-sided “natural variability” seems unlikely.

I asked Dr Ding how confident he was about this claim, in other words, would he be willing to quantify the “may” in “… may be responsible...” in the attribution claim in the abstract. In other words, is there a 90% chance that “30-50% of the overall decline in September sea ice since 1979” is attributable to natural climate variability, in which case the apparently preposterous claim should be taken seriously by policy makers that previously were concerned about the disappearance of Arctic sea ice as a serious indicator that radical emissions reduction policies should be put in place ASAP? Or is it the case that the authors are only 10% confident about this particular claim (and so it should not be found in the abstract in the first place)?

The problem is that the 2017 Ding et al paper lacks any uncertainty analysis of this particular claim. The “30-50%” range in attribution to natural variability is derived in the paper from two different sets of reanalysis products (NCEP2 and MERRA2) that indicate very different trends in GL-Z200. This in detailed in lines 253-261 of the paper:
“The impact of observational uncertainties on our conclusions can be estimated by linearly scaling the results from Exp-6 by the GL-Z00 trends extracted from different reanalyses products. The atmospheric circulation contribution to sea ice loss ranges from 48% (NCEP-2) to 75% (MERRA-2). Using the 70% contribution of internal forcing to the circulation variability established above, we can attribute 30-50% of sea ice loss to internal variability.
Reanalysis products are reliable representations of the observed circulation, humidity and temperature. The reanalysis data probably also reliably represent the variability in total cloud cover in the satellite era, particularly in summer.”

As we can see, the “30-50%” range already relies on a series of mostly unwarranted assumptions, even before we question the skill of the model used in Exp-6.
Let’s list just a couple of these assumptions:
1) It is assumed that the two different sets of reanalysis products (NCEP2 and MERRA2) represent the extremes for the range of atmospheric circulation contribution to sea ice loss ranges. This is an extremely important assumption and yet there is absolutely no reason for this to be true.
2) The assumption that reanalysis data for the period 1979-2014 for GL-Z200 closely represents the reality of atmospheric circulation over the entire Arctic region. This is an essential assumption in the paper and yet it is inherently questionable, specially when we know that reanalysis data for GL-Z200 is derived from observations from a limited number of meteorological stations along the coast of Greenland. Just looking at a map of the Arctic one realizes that generalizing the weather or atmospheric circulation over the southern coast of Greenland to the whole Arctic region is more of a leap of faith than a scientifically justifiable assumption (see attached map).

If we roughly estimate the uncertainty in the reanalysis product data at +/- 15% (with 95% confidence), and the uncertainty over the generalization of GL-Z200 to the entire Arctic region at +/- 25% (again with 95% confidence), we can rewrite the original attribution claim as follows:

“Internal variability dominates the Arctic summer circulation trend and may be responsible (with 95% confidence) for about 0-80% of the overall decline in September sea ice since 1979.”

Now, of course this still assumes the sea ice model (POP2+CICE4) used by Ding et al in Exp-5 and Exp-6 to be perfectly skillful, but we know this is not the case since none of the existing sea ice models correctly predict the decline of Arctic sea ice, as indicated in the Notz and Stroeve paper.
And also note that whatever error/uncertainty added by the POP2+CICE4 model used by Ding et al must be doubled when stating the attribution claim, which is derived from the difference between two model runs with different sets of data.

Let’s roughly estimate the uncertainty in the POP2+CICE4 model at +/- 20% (with 95% confidence). We must now rewrite the original attribution claim in a final form:

“Internal variability dominates the Arctic summer circulation trend and may be responsible (with 95% confidence) for about -40 to +120% of the overall decline in September sea ice since 1979.”

Which of course it is a totally meaningless claim, and would expose the eleven co-authors, including Ding himself, to ridicule.

I am not claiming my back of the envelope uncertainty analysis is correct, but unfortunately the Ding et al is lacking in this area (despite the numerous caveats), which makes it quite useless as a basis for policy makers, and in my not so humble opinion, of little if any scientific value.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 11, 2017, 07:20:41 PM
@  Archimid @ Cid_Yama

Why you are talking Bullshit? There is nothing wrong with the paper and all what you both said is totally wrong, they used the forced response of the models, this include not just co2, its also include ch4, sox, landuse, black-carbon... they also say, that some part of unforced atmosphere pattern could be a result of feedback to the ice loose itself, but they claim more to natural impact, as i shown here, it could be also not natural (in context of most) and this is the only point for critics to the paper, or in other words, there conclusion is not so confident that the last word would be spoken about it.

So, you both making the same shit, as the denials of global warming, you are also trapped in your own world, without any kind of open mind


1.  The term 'natural variability' is assigned to global atmospheric circulation patterns that are largely driven by the tropical pacific surface water temperature cycles (ENSO)

2.  Recent studies have confirmed that the REGIONAL impacts of point-source SOx emissions (and volcanoes) drove the 'natural variability' cycles in the tropical pacific.  see:  http://www.nature.com/nclimate/journal/v6/n10/full/nclimate3058.html (http://www.nature.com/nclimate/journal/v6/n10/full/nclimate3058.html)

Quote
Our results suggest that a slowdown in GMST trends could have been predicted in advance, and that future reduction of anthropogenic aerosol emissions, particularly from China, would promote a positive PDO and increased GMST trends over the coming years.

3. The key period identified in the Ding et al paper was the shift to +IPO in the period between 2003 and 2005 (prior to the 2007 'black swan' ice loss and then again in 2012.  In their analysis they DID NOT INCLUDE REGIONAL SO2 FORCING AS A DRIVER.

The key point of the problem is revealed when one looks at the actual chinese rampup and drawdown of SO2 emissions for power generation during this period. 

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fiopscience.iop.org%2F1748-9326%2F8%2F1%2F014003%2FdownloadFigure%2Ffigure%2Ferl441620f1&hash=a5d92767564d379beab424b888e8d611)

now that china has shut down its high-sulfur coal production and shifting to cleaner sources of power generation, we are now seeing the wider impacts of these aerosol emissions in ways that are apart from global forcing and directly impact atmospheric circulation patterns that have previously been ascribed as 'natural variability'.

1.  The sea ice is melting out 40 years ahead of the models
2.  slightly more than 1/2 of the total GMST warming since the industrial era is currently being offset by SOx emissions
3.  When the Arctic melts out changes in albedo alone will increase GMST by over 0.5C
4.  the IPCC did not include permafrost emissions in their RCP emission scenarios.
5.  Without a national (U.S.) mobilization utilizing non-market forces to transform our economy away from fossil fuels on a single decade timescale, we will be unable to prevent +4C and global warming will kill your children.
6.  We need to stop allowing our scientific body to act like these things are not real and currently happening.  we need to address this technical issue now and not dilly-dally about magical +1.5C emission scenarios as though they exist.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: seaicesailor on April 11, 2017, 07:38:57 PM
6.  We need to stop allowing our scientific body to...
Didn't the last POTUS tweet start along similar phrasing?
Why don't we let the scientists alone do their fine good job?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: seaicesailor on April 11, 2017, 07:43:20 PM
Actually, why don-'t we LEAVE SCIENTISTS ALONE now that they are being actively prosecuted, buried, insulted by Trump????????????????????????????????????????
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 11, 2017, 07:47:16 PM
6.  We need to stop allowing our scientific body to...
Didn't the last POTUS tweet start along similar phrasing?
Why don't we let the scientists alone do their fine good job?

Individual science work is vital and necessary and good.  As a collective body, working within political frameworks, the IPCC has done a great disservice to humanity and there should be selection for lead author contribution to a mea culpa that will act as the preamble to the IPCC 2017 Summary for Policymakers.

https://www.theguardian.com/environment/earth-insight/2014/may/15/ipcc-un-climate-reports-diluted-protect-fossil-fuel-interests (https://www.theguardian.com/environment/earth-insight/2014/may/15/ipcc-un-climate-reports-diluted-protect-fossil-fuel-interests)

IPCC reports 'diluted' under 'political pressure' to protect fossil fuel interests
Saudi-led coalition sought to make policy summaries as vague as possible to minimise climate action
Quote
Far from being too alarmist, these criticisms suggest that the IPCC's summary reports are too conservative. Like Wasdell, Broome describes how "a coalition of countries led by Saudi Arabia" at the April approval session in Berlin "insisted" that all "figures" depicting increases of greenhouse gas emissions in countries classified by 'income group' "should be deleted."

Saudi Arabia, he said, also "wanted to delete all references to any part of the main report that mentioned income groups… in the end Saudi Arabia got its way completely."

Quote
Global Warming will kill your children
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 11, 2017, 08:06:40 PM

No, this is NOT what scientists think.  They look for patterns that emerge in the model ensembles with and without AGW (CO2) forcing and compare to observations.  Those observations that do NOT emerge with AGW forcing either indicate a flaw in the model or natural variation.

I believe that what you said is exactly what they think. There is a good logic to it. Their elaborate and continuously updated and tested models can predict with very good accuracy certain aspect the climate system. They can be very insightful tools.  I can agree that withing the limits of the models, attributing up to 60% of Arctic sea ice loss to the natural variation of the models maybe acceptable.

However, when seen under other lines of evidence the claim that what they found is due to natural variability does not hold.

First, Arctic recent history. The evidence I have seen clearly indicate that the arctic was pretty much a constant size since 1850. See the first image , taken from what I think is the best article on Arctic Recent history here:
https://www.carbonbrief.org/guest-post-piecing-together-arctic-sea-ice-history-1850 (https://www.carbonbrief.org/guest-post-piecing-together-arctic-sea-ice-history-1850)


I see no 60 year / 100 year or any type of cycle visible that would account for 60% sea ice loss.


Then when I look at the 20,000 year temperature record, (second image) it is obvious that for the last 500 years the world was much colder than the 20th century, so it is not a stretch to assume that the Arctic was as nice and healthy as it was during the 20th century.

image URL: https://tamino.files.wordpress.com/2013/03/shakun_marcott_hadcrut4_a1b_eng.png (https://tamino.files.wordpress.com/2013/03/shakun_marcott_hadcrut4_a1b_eng.png)

Then there is the beginning of the Holocene which was about as warm as it is now but for thousands of years. That's the only time there could have been and ice free arctic that I would attribute to natural variation.

So the evidence points at something other than natural variation for the Arctic sea ice loss. The evidence clearly points at anthropogenic forces being responsible for not only the 40 % due to CO2 forcing and other modeled phenomena, but also for much of the 60% forcing that the random noise of the models point to.

That is the reason I attack the conclusion that up to 60% of Arctic sea ice loss is due to natural variability. It is 100% due to human influence. That the Atmosphere may be a bigger driver than other AGW attributable things, I don't doubt it for a second. That the atmospheric variations are due to natural variation? I don't believe it for a second.



Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 11, 2017, 09:18:40 PM
Folks, let's not do the re-run of this show, okay?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Blizzard92 on April 11, 2017, 09:22:03 PM
Commentary in response to the Ding et al. [2017] paper:

Climate variability: Natural causes of Arctic sea-ice loss [Swart N., 2017]
http://www.nature.com/nclimate/journal/v7/n4/full/nclimate3254.html (http://www.nature.com/nclimate/journal/v7/n4/full/nclimate3254.html)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 11, 2017, 09:23:27 PM
Archimid,

"1.  The sea ice is melting out 40 years ahead of the models"

Not correct at all, because as i shown, the models had different model sea ice states, the model with the most realistic model sea ice state, has no problem to loose much ice as we saw in observation

"2.  slightly more than 1/2 of the total GMST warming since the industrial era is currently being offset by SOx emissions"

Speculation on the upper Band, its not clear yet  how much, its arround -0.2K up to-0.8K

"3.  When the Arctic melts out changes in albedo alone will increase GMST by over 0.5C"

And deep water formation also change, which cools, never foreget, the atlatic site is always warmer because of MOC, would ice be gone, melt of Greenland intens, MOC would slow down and cancel some warming out.. what about increase of albedo on landside in the arctic, more greening means more albedo also increase in cloudcover and and and

"4.  the IPCC did not include permafrost emissions in their RCP emission scenarios."

Why should, dont you understand that this is a model output, not a imput, the model physics make it up how much is released

"5.  Without a national (U.S.) mobilization utilizing non-market forces to transform our economy away from fossil fuels on a single decade timescale, we will be unable to prevent +4C and global warming will kill your children."

Yeah, sounds confident by someone who is not knowing about imputs and outputs in models :-)

"6.  We need to stop allowing our scientific body to act like these things are not real and currently happening.  we need to address this technical issue now and not dilly-dally about magical +1.5C emission scenarios as though they exist."

The really first thing to do is, tpo wipe out people who deny climate change is real and people who always say we unable to prevent it (as you)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 11, 2017, 10:41:07 PM
Neven,

"Folks, let's not do the re-run of this show, okay?"

Soory, cant let this stand so, some claims here about the paper are so far away from reality that it hurts
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: sidd on April 11, 2017, 11:35:15 PM
Heres a paper that may be relevant: doi:10.5194/tc-2017-39

From the abstract:

" Downward longwave radiation is an essential element for sea ice reduction, but can only be sustained by excessive upward heat flux from the sea surface exposed to air in the region of sea ice loss. The increased turbulent heat flux is used to increase air temperature and specific humidity in the lower troposphere, which in turn increases downward longwave radiation ... A quantitative assessment reveals that this feedback process is amplifying at the rate of ~ 8.9 % every year during 1979–2016. Based on this estimate, sea ice will completely disappear in the Barents and Kara Seas by around 2025. Availability of excessive heat flux is necessary for the maintenance of this feedback process; a similar mechanism of sea ice loss is expected to take place over the sea-ice covered polar region when sea ice is not fully recovered in winter."

Open access. Read all about it:

http://www.the-cryosphere-discuss.net/tc-2017-39/ (http://www.the-cryosphere-discuss.net/tc-2017-39/)

sidd
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 11, 2017, 11:45:53 PM
Neven,

"Folks, let's not do the re-run of this show, okay?"

Sorry, cant let this stand so, some claims here about the paper are so far away from reality that it hurts

Random_Weather    +1

Zach Labe - thanks for the link to the Neil Swart comment that appeared in NATURE CLIMATE CHANGE.  Here are the paragraphs that matter:

Quote
The challenge, until now, is that there has been no clear understanding of the relative contributions of human-induced warming versus internal variability to the observed long-term decline in Arctic sea ice.

Ding et al. make a significant advance in this area by estimating the contribution of internal variability to the observed long-term sea-ice decline. Beginning with a statistical analysis, they show that observed September near-surface warming and seaice loss are strongly correlated with changes in the upper-level atmospheric circulation centered over Greenland. To determine the causality of these changes, the authors conduct a novel series of model simulations that show that the circulation change is indeed a driver of, not a response to, the sea-ice loss. Remarkably, their simulations suggest that the large-scale atmospheric circulation changes could be responsible for up to 60% of observed summer-time Arctic sea-ice loss since 1979.

If the circulation changes are caused by anthropogenic greenhouse warming (or other human or natural external forcings such as ozone depletion, aerosol emissions, or solar activity) this pattern of atmospheric change should emerge as a clear signature when averaging together many climate model simulations of this period. Averaging together many simulations effectively cancels out all random internally generated fluctuations seen in individual climate simulations, leaving behind the model response to external forcings, such as increasing greenhouse gases. Using this approach, Ding et al. find that external forcing accounts for very little of the observed circulation changes, and therefore attribute the changes predominantly to internally generated variability. The result is surprising, in that it attributes a multidecadal atmospheric circulation anomaly to internal variability. Typically, internal variability is most prominent at shorter timescales — from months to years — and accounts for less of the observed variability as one extends to longer and longer timescales. The simulation-averaging approach they use to make this attribution is common, but it relies on the assumptions that the models have been supplied with the correct forcing, and are faithfully replicating the real world response to that forcing — assumptions that are always open to question. Nonetheless,multi-decadal-scale internal variability does exist, most often relying on the longerterm memory of the ocean. For example, tropical Pacific sea surface temperature(SST) variability has been shown to have a strong connection with atmospheric circulation anomalies over Greenland and Arctic sea ice . Thus, there is a plausible link between tropical SST variability and Arctic sea-ice decline, but firmly establishing this relationship would require further work. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on April 11, 2017, 11:49:18 PM
My only complaint about the "alarmists" viewpoint is the claim that we need to do anything.  First I think it is too late to do anything, and second I think that trying to do anything is likely to lead to an even worse result.

We screwed up the climate with the Industrial Revolution.  End of story.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 12, 2017, 12:36:47 AM
A quick commentary on the commentary by Neil Swart.
Quote from: Neil Swart
The challenge, until now, is that there has been no clear understanding of the relative contributions of human-induced warming versus internal variability to the observed long-term decline in Arctic sea ice.

I don't think this has been the challenge. I think the challenge is that sea ice models until now have failed to explain the rapid decline in Arctic sea ice, as stated in the Notz and Stroeve 2016 article which I have mentioned in one of my previous comments.

Quote from: Neil Swart
Ding et al. make a significant advance in this area by estimating the contribution of internal variability to the observed long-term sea-ice decline. Beginning with a statistical analysis, they show that observed September near-surface warming and sea ice loss are strongly correlated with changes in the upper-level atmospheric circulation centered over Greenland. To determine the causality of these changes, the authors conduct a novel series of model simulations that show that the circulation change is indeed a driver of, not a response to, the sea-ice loss. Remarkably, their simulations suggest that the large-scale atmospheric circulation changes could be responsible for up to 60% of observed summer-time Arctic sea-ice loss since 1979.

Is that really that remarkable? There are only two physical mechanisms by which heat from the tropics can be carried to the Arctic, namely atmospheric circulation or oceanic currents. And we know already that intrusions of warm, moist air from the tropics in the Arctic during summer will result in extra melt and lower sea ice extent in September.

The fact is that these intrusions of warm, moist air from the tropics did not seem to occur before, and now they do. And that's where the attribution question arises.

Quote from: Neil Swart
If the circulation changes are caused by anthropogenic greenhouse warming (or other human or natural external forcings such as ozone depletion, aerosol emissions, or solar activity) this pattern of atmospheric change should emerge as a clear signature when averaging together many climate model simulations of this period. Averaging together many simulations effectively cancels out all random internally generated fluctuations seen in individual climate simulations, leaving behind the model response to external forcings, such as increasing greenhouse gases. Using this approach, Ding et al. find ...

There is no mention in the Ding et al paper that they "average together many simulations". They don't use this method, actually what they do is run the POP2+CICE4 model with two sets of data, and subtract the results from one run from the results from the other run.

Quote from: Neil Swart
...
that external forcing accounts for very little of the observed circulation changes, and therefore attribute the changes predominantly to internally generated variability. The result is surprising, in that it attributes a multidecadal atmospheric circulation anomaly to internal variability. Typically, internal variability is most prominent at shorter timescales — from months to years — and accounts for less of the observed variability as one extends to longer and longer timescales.
(emphasis mine) That's the objection that many have stated here in many different ways, but in a few words: nearly 40 years of one-sided variability seems unlikely.

Quote from: Neil Swart
...
The simulation-averaging approach they use to make this attribution is common,...

Again, Ding et al don't use a simulation-averaging approach.

Quote from: Neil Swart
...
but it relies on the assumptions that the models have been supplied with the correct forcing, and are faithfully replicating the real world response to that forcing — assumptions that are always open to question.

That is exactly my objection above that they didn't properly quantify the uncertainties associated with the reanalysis data that they fed their POP2+CICE4 model in Exp-5 and Exp-6.

Quote from: Neil Swart
...
Nonetheless,multi-decadal-scale internal variability does exist, most often relying on the longer term memory of the ocean. For example, tropical Pacific sea surface temperature(SST) variability has been shown to have a strong connection with atmospheric circulation anomalies over Greenland and Arctic sea ice . Thus, there is a plausible link between tropical SST variability and Arctic sea-ice decline, but firmly establishing this relationship would require further work. 

This latter question is purely of academic interest.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 12, 2017, 01:51:22 AM
Quote
If the circulation changes are caused by anthropogenic greenhouse warming (or other human or natural external forcings such as ozone depletion, aerosol emissions, or solar activity) this pattern of atmospheric change should emerge as a clear signature when averaging together many climate model simulations of this period.

Unfortunately. . .

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0362.1 (http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0362.1)

Indirect Aerosol Effect Increases CMIP5 Models’ Projected Arctic Warming

Petr Chylek et al.

Abstract:  Phase 5 of the Coupled Model Intercomparison Project (CMIP5) climate models’ projections of the 2014–2100 Arctic warming under radiative forcing from representative concentration pathway 4.5 (RCP4.5) vary from 0.9° to 6.7°C. Climate models with or without a full indirect aerosol effect are both equally successful in reproducing the observed (1900–2014) Arctic warming and its trends. However, the 2014–2100 Arctic warming and the warming trends projected by models that include a full indirect aerosol effect (denoted here as AA models) are significantly higher (mean projected Arctic warming is about 1.5°C higher) than those projected by models without a full indirect aerosol effect (denoted here as NAA models). The suggestion is that, within models including full indirect aerosol effects, those projecting stronger future changes are not necessarily distinguishable historically because any stronger past warming may have been partially offset by stronger historical aerosol cooling. The CMIP5 models that include a full indirect aerosol effect follow an inverse radiative forcing to equilibrium climate sensitivity relationship, while models without it do not.

----------------------------

even IF they used an average, the average between the models shows inherent internal bias AGAINST exposing the new apparent mechanism of tropical SST impacts from SE Asian aerosols since this effect is NOT represented in most of the CMIP5 models.

. . .so it must be 'natural variability'.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 12, 2017, 04:25:40 AM
Thanks Ktonine, for quoting from the Swart paper.
Swart also adds :
Quote
Robustly establishing that such a large fraction of observed Arctic summer-time sea-ice loss can be attributed to internal variability will need independent observational corroboration.
Can’t argue with that…:o)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 12, 2017, 04:29:23 AM
ktonine wrote :
Quote
Obviously they've gone over the models dozens of times trying to figure out why they don't match observations.  At some point (Ding et al) someone was bound to come up with the rational idea that maybe it's not being entirely forced, but simply natural variation.

Interesting is Swart’s graph from the Canadian Earth System Model version 2 model runs, which pretty nicely match observations.
So your argument may not hold ground.

The point is, some CMIP5 models are bad and some CMIP5 models are good.
You can't use the bad models (or the mean) as an argument that the lack of match with observations is caused by 'internal variability'.

As Michael Mann wrote :
https://twitter.com/MichaelEMann/status/841362467603255298
Quote
But misfit relative to CMIP5 mean doesn't imply internal variability!
CMIP5 mean likely does NOT capture true forced trend.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 12, 2017, 04:32:33 AM
Archimid,

"1.  The sea ice is melting out 40 years ahead of the models"

. . .

That was my post, not archimids,

1.  I was referring to the current CMIP5 ensemble used in the IPCC projections for future arctic sea ice loss.  The most aggressive model does show sea ice loss (effective september minimum) at about the right time (next 2-5 years).

2. Even the band of 0.2K to 0.8K produced by the CMIP5 model ensemble is understating since they do not include water vapor and lapse rate feedbacks produced by SOx emissions reductions.  In addition, the known issue of indirect cloud effects being poorly modeled (and even absent from about 1/2 of the CMIP5 ensemble) shows that the actual range is 0.5K to 1.3K being currently offset by anthropogenic SO2 emissions

3.  The albedo effect of an ice-free arctic is well studied and a 0.5K increase in GMST is actually a conservative figure.  I assert that we are actually well on our way to have JUNE 21st ice free conditions in the total absence of SO2 emissions and BAU global carbon emissions for the next 10 years.  (I project this summer solstice ice free state to occur sometime around 2065).  This will produce over 1.5C of GMST warming in pure albedo with over 70w/m^2 annual shortwave additional forcing over the Arctic ocean - this is verified by NASA satellite analysis of the Bearing Sea published in 2014.

4.  The IPCC included other carbon cycle feedbacks in their CMIP5 ensemble, including a projection of Atmospheric Fraction.  To not include this massive feedback is to severely understate our current climate crisis.   Leading to policy directions that do not serve to meet the existential crisis that is global warming.

5.  I know that even with a WWII mobilization effort we may not be able to prevent +4C in globally averaged warming and we will likely be forced to engage in global dimming geoengineering.

6.  I do not say we are unable to prevent it, I am saying that we have already surpassed the +3.5C CO2e abundance levels if we include the following feedbacks that are not included in the CMIP5 model ensemble.

Quote
early sea ice loss albedo
increase in arctic algae bloom further increasing albedo loss
Near persistent +IPO leading to collapse of the Amazon Rainforest
Rapid collapse of arctic permafrost
collapse of the boreal forest system due to heat stress/drought
ocean acidification causing a long-term loss of the production of Dimethyl Sulfide
reduction in far-infrared emission from the Arctic ocean as sea ice is lost
much greater warming soils carbon feedback (not frozen soils) than contained in the current model ensemble


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 12, 2017, 05:30:41 AM
Qinghua Ding was kind enough to reply to my post regarding the 'attribution' experiment (Exp 7/8), in a private email, explaining this experiment in more detail :
Quote
In our Exp7 and 8, we repeated our exp2 ( in which we specified the observed winds everywhere in the model)  but removed the CO2 forced wind changes (1979 to 2014) from the observed winds. The CO2 forced winds were derived from CMIP5/LENS runs that were only forced by anthropogenic forcing. In other words, we wanted to see how much atmospheric warming would be left in the Arctic if we could remove any winds that is due to CO2 forcing. We found that there are still 70% to 90% of atmospheric warming left in Exp7 and 8 ( compared with Exp2).  This is how we dealt with that attribution. I don't think the method you described is similar to what we did in Exp7 and 8. 
It seems to me that if you want to tease out the 'anthropogenic' part of the warming trend, that you should not just eliminate the "CO2 forced wind changes", but you should also include the much more obvious "CO2 forced" factor : Temperature !

This is my main criticism of the Ding et al 2017 paper : At no point (neither in the 'causation' (Exp.5/6) nor in the 'attribution' part (Exp 7/8) did they even attempt to address the influence of AGW, the KEY 'anthropogenic' factor in this game.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 12, 2017, 05:41:22 AM
Interesting is Swart’s graph from the Canadian Earth System Model version 2 model runs, which pretty nicely match observations.
So your argument may not hold ground.

The point is, some CMIP5 models are bad and some CMIP5 models are good.
You can't use the bad models (or the mean) as an argument that the lack of match with observations is caused by 'internal variability'.

Rob - don't get blinded again.  Whether a particular model does or does not "match observations" isn't the key point. The key point is does it match observations *because* the AGW forcing also creates the key atmospheric pattern?  If it matches observations but doesn't match the circulation pattern, then it's probably just coincidence or particular attention was paid to "tuning" parameters where possible to better match observations.

I think it highly, highly unlikely that Ding or Swart haven't already considered and evaluated this to some degree.  You'd expect Swart as a noted climate modeler, and of a model that *does* reproduce observations well, to take the *opposite* view of Ding et al.

The ensemble mean is still the best guess unless it can be shown that excluded models all suffer some physical flaw.  Hansen's tour de force "Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous" was impressive because they *did* find and fix several flaws they found in the model they were using - notably I recall they were able to fix the model so that Antarctic Bottom Water formation took place in the correct geographical location.

In any event, believing a paper is or isn't completely correct isn't what I objected to - I'm agnostic on Ding et al.   The rude, asinine, and flatout character assassination of the Ding et al authors by some here (not you) is what riled me up. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 12, 2017, 05:50:52 AM
This is my main criticism of the Ding et al 2017 paper : At no point (neither in the 'causation' (Exp.5/6) nor in the 'attribution' part (Exp 7/8) did they even attempt to address the influence of AGW, the KEY 'anthropogenic' factor in this game.

We're going down the rabbit hole again. From Ding et al, METHODS Exp-6: "Given a strong correlation between circulation and surface winds, temperature, specific humidity, sea-level pressure, and downwelling long wave radiation in the Arctic,variability and trends in these six variables that are associated with Z200GL are processed and removed from the forcing.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Darvince on April 12, 2017, 07:01:30 AM
A quick commentary on the commentary by Neil Swart.
Quote from: Neil Swart
The challenge, until now, is that there has been no clear understanding of the relative contributions of human-induced warming versus internal variability to the observed long-term decline in Arctic sea ice.

I don't think this has been the challenge. I think the challenge is that sea ice models until now have failed to explain the rapid decline in Arctic sea ice, as stated in the Notz and Stroeve 2016 article which I have mentioned in one of my previous comments.
Um, both are completely connected and interdependent on one another. If 30-60% of the sea ice loss trend is naturally forced, then wouldn't the model mean fail to show the sea ice loss trend that was observed? This directly happened with the small rise in Antarctic sea ice when models predicted a small loss over the past 40 years. Does this mean the models were bad? No, it means that trends elsewhere in the world unconnected to climate warming caused the sea ice gain in the south. In fact, posted in two placed by AbruptSLR he links papers which show that the gain in Antarctic sea ice over the last decade and a half was due to the IPO climate oscillation (and, apparently, the more rapid loss of Arctic sea ice since ~2000):

http://forum.arctic-sea-ice.net/index.php/topic,1053.msg94192.html#msg94192 (http://forum.arctic-sea-ice.net/index.php/topic,1053.msg94192.html#msg94192)
http://forum.arctic-sea-ice.net/index.php/topic,724.msg82561.html#msg82561 (http://forum.arctic-sea-ice.net/index.php/topic,724.msg82561.html#msg82561)

Now, what can actually make the finding by Ding et al. irrelevant would be showing that the recent negative phase of the IPO was directly due to anthropogenic sources.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 12, 2017, 07:23:16 AM
Now, what can actually make the finding by Ding et al. irrelevant would be showing that the recent negative phase of the IPO was directly due to anthropogenic sources.

http://www.nature.com/nclimate/journal/v6/n10/full/nclimate3058.html (http://www.nature.com/nclimate/journal/v6/n10/full/nclimate3058.html)

Role of volcanic and anthropogenic aerosols in the recent global surface warming slowdown

Doug M. Smith et al.

The rate of global mean surface temperature (GMST) warming has slowed this century despite the increasing concentrations of greenhouse gases. Climate model experiments1, 2, 3, 4 show that this slowdown was largely driven by a negative phase of the Pacific Decadal Oscillation (PDO), with a smaller external contribution from solar variability, and volcanic and anthropogenic aerosols5, 6. The prevailing view is that this negative PDO occurred through internal variability7, 8, 9, 10, 11. However, here we show that coupled models from the Fifth Coupled Model Intercomparison Project robustly simulate a negative PDO in response to anthropogenic aerosols implying a potentially important role for external human influences. The recovery from the eruption of Mount Pinatubo in 1991 also contributed to the slowdown in GMST trends. Our results suggest that a slowdown in GMST trends could have been predicted in advance, and that future reduction of anthropogenic aerosol emissions, particularly from China, would promote a positive PDO and increased GMST trends over the coming years. Furthermore, the overestimation of the magnitude of recent warming by models is substantially reduced by using detection and attribution analysis to rescale their response to external factors, especially cooling following volcanic eruptions. Improved understanding of external influences on climate is therefore crucial to constrain near-term climate predictions.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 12, 2017, 08:00:12 AM
This is my main criticism of the Ding et al 2017 paper : At no point (neither in the 'causation' (Exp.5/6) nor in the 'attribution' part (Exp 7/8) did they even attempt to address the influence of AGW, the KEY 'anthropogenic' factor in this game.

We're going down the rabbit hole again. From Ding et al, METHODS Exp-6: "Given a strong correlation between circulation and surface winds, temperature, specific humidity, sea-level pressure, and downwelling long wave radiation in the Arctic,variability and trends in these six variables that are associated with Z200GL are processed and removed from the forcing.

My point exactly.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 12, 2017, 08:11:06 AM
Interesting is Swart’s graph from the Canadian Earth System Model version 2 model runs, which pretty nicely match observations.
So your argument may not hold ground.

The point is, some CMIP5 models are bad and some CMIP5 models are good.
You can't use the bad models (or the mean) as an argument that the lack of match with observations is caused by 'internal variability'.

Rob - don't get blinded again.  Whether a particular model does or does not "match observations" isn't the key point. The key point is does it match observations *because* the AGW forcing also creates the key atmospheric pattern?  If it matches observations but doesn't match the circulation pattern, then it's probably just coincidence or particular attention was paid to "tuning" parameters where possible to better match observations.

Mmm. Are you suggesting that Swart's Canadian Earth System Model version 2 model was " "tuning" parameters where possible to better match observations" ?
Or could it just be a better model ?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 12, 2017, 10:39:19 AM
A quick commentary on the commentary by Neil Swart.
Quote from: Neil Swart
The challenge, until now, is that there has been no clear understanding of the relative contributions of human-induced warming versus internal variability to the observed long-term decline in Arctic sea ice.

I don't think this has been the challenge. I think the challenge is that sea ice models until now have failed to explain the rapid decline in Arctic sea ice, as stated in the Notz and Stroeve 2016 article which I have mentioned in one of my previous comments.
Um, both are completely connected and interdependent on one another. If 30-60% of the sea ice loss trend is naturally forced, then wouldn't the model mean fail to show the sea ice loss trend that was observed?
There are many possible reasons why the model mean could fail to explain the observed Arctic sea ice decline. For example:
- Lack of sufficiently accurate weather data over the Arctic ocean during the period considered.
- Most models not including some positive or negative feedbacks that have only recently been uncovered.
- The particular complexity of the Arctic climate system and how it interacts with the global climate system may not be captured by the model mean.

Ding et al instead chose to stroll down "natural climate variability" argument path, but that was because they had already done so in their 2014 paper about warming in the eastern Canada and Greenland region. As I wrote in one of my previous comments, the 2017 Ding et al paper makes similar assumptions, uses a similar methodology and reaches a similar conclusion, as the Ding et al 2014 paper. It doesn't mean that both papers are correct.

Quote from: Darvince
This directly happened with the small rise in Antarctic sea ice when models predicted a small loss over the past 40 years. Does this mean the models were bad? No, it means that trends elsewhere in the world unconnected to climate warming caused the sea ice gain in the south. In fact, posted in two placed by AbruptSLR he links papers which show that the gain in Antarctic sea ice over the last decade and a half was due to the IPO climate oscillation (and, apparently, the more rapid loss of Arctic sea ice since ~2000):

http://forum.arctic-sea-ice.net/index.php/topic,1053.msg94192.html#msg94192 (http://forum.arctic-sea-ice.net/index.php/topic,1053.msg94192.html#msg94192)
http://forum.arctic-sea-ice.net/index.php/topic,724.msg82561.html#msg82561 (http://forum.arctic-sea-ice.net/index.php/topic,724.msg82561.html#msg82561)

Now, what can actually make the finding by Ding et al. irrelevant would be showing that the recent negative phase of the IPO was directly due to anthropogenic sources.

In the second part of my first question to Dr. Ding, I asked him exactly that: what scientific experiment or physical evidence would prove his "natural variability" attribution claim wrong.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 12, 2017, 06:13:59 PM
My point exactly.
Rob - you're not making sense.  When they ran the same simulations with and without AGW influence how can that possibly be characterized as not trying to determine the effects of AGW?  That's what Exp-5/6 were about. 

You may not like the specific design. OK, all that sounds like is I'm smarter than them and would have designed the experiment differently.

Mmm. Are you suggesting that Swart's Canadian Earth System Model version 2 model was " "tuning" parameters where possible to better match observations" ?
Or could it just be a better model ?
[/quote]

Of course it *could* just be a better model. Assume that it is.  Then Dr Swart should be critical of the Ding et al results if he bought into your objections - not complimenting them.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 12, 2017, 06:24:55 PM
So many interesting discussions!
 
Just a quick answer to AndrewB. I will have more to add this weekend.

If you can show me an ensemble mean ( more than 10 to 20+ realizations) of multiple models forced by anthropogenic forcing ( whatever you like to add in the models, Co2, aerosol, land surface use and ozone etc ) that can well capture the observed circulation change in the past 40 years. I think this would be a good evidence that my argument is wrong. If not, we have to say that a portion of observed circulation change is due to a natural source and this part of natural source can melt sea ice through a dynamical impact rather than the greenhouse effect.
 
Please read our papers in 2014 (fig. 4) and 2017(fig.4) . We checked all available models to do this analysis and we couldn't find a similarity. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 12, 2017, 06:29:21 PM
This is also a very interesting article from Dr. Swart published in 2015.

Swart, N. C., Fyfe, J. C., Hawkins, E., Kay, J. E. & Jahn, A. Influence of internal variability on Arctic sea-ice trends. Nat. Clim. Change 5, 86–89 (2015).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 12, 2017, 08:08:39 PM
Dr. Ding

So many interesting discussions!
 
If you can show me an ensemble mean ( more than 10 to 20+ realizations) of multiple models forced by anthropogenic forcing ( whatever you like to add in the models, Co2, aerosol, land surface use and ozone etc ) that can well capture the observed circulation change in the past 40 years.

In my opinion this is overconfidence in models, on global scale i would agree but in arctic i would be carefully and it seem not to be a problem of forcing representation, but more in the models(the mean of it) state of cyrosphere. In fact, if we looking for september sea ice concentration we get this: (SIC for 70-90N)

http://fs5.directupload.net/images/170328/hq2ruz53.png (http://fs5.directupload.net/images/170328/hq2ruz53.png)

Over the complete Hindcast, the mean of models have to less ice concentration in september against observation, also lower trend, this is a result (look also Q. Shu 2015: Assessment of sea ice simulations in the CMIP5) of that the models have complete different states of sea ice Annual Extent, Aplitude and Trend, as shown above the mean of the models is totaly different to the observation, also shown is MPI-ESM-MR and it works well with observation. So whats different,  MPI-ESM-MR has the most realitic sea ice state untill 2005(Annual-Extent, Aplitude and Trend) and therefore in forecast also the best. In forecast, we see that the ups and downs are different, which imply a different phase of internal variability. So i would tend to say, still if physics of models were perfect, they are not able the produce the real world aplification of regional climate system because of the lack of representation of cyrosphere state in the hindcast.

Under the line, it seem not confident to me to claim it would be more natural source, because of the lack of cyrosphere representation in models. Also to say, if you test z200 JJA CIMP5 and JJA SIC CIMP5 you will get R^2= 0.925 (1979 to 2016), which imply that SIC in JJA and z200 JJA are strongly connected, since the models undereastimate the Trend, they will also undereastimate z200 Trend for JJA


To make a clear point:
I would not say your Paper is wrong or any kind of it, but the results(in magnitude) seem to me not so confident and there is more research needed

Edit:
Sources:
KMNI-Explorer SIC NSIDC between 70-90N
KMNI-Explorer SIC CMIP5 mean between 70-90N
KMNI-Explorer SIC MPI-ESM-MR between 70-90N
KMNI-Explorer z200 CMIP5 mean between 70-90N (JJA)
KMNI-Explorer SIC CMIP5 mean between 70-90N (JJA)

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 12, 2017, 08:33:32 PM
Thanks. My quick answer to Random_Weather is that I realize many people here really like to use a domain mean or a global mean plot. In my view, that could be misleading to some extents. Some models could get the correct sign of a change due to a wrong reason. So I believe I need to see the spatial pattern first ( not only sea ice ) and then make a conclusion.  I will show you more evidences why I say so this weekend once I find some time.
 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 12, 2017, 08:49:02 PM
Dr. Ding, Thanks for fast reply

"So I believe I need to see the spatial pattern first"

This would also change the spatial pattern, in your Paper you show CIMP5 in average and the atmosphere modul of MPI-ESM-MR and it show clear the same spatial pattern like in observation just a bit weaker, but CIMP5-mean is fail to reproduce the pattern. It brings me to the question, why the model MPI-ESM-MR can produce it and have one of the best representations in Hindcast of cyrosphere state (Annual-Extent, Trend and Aplitude). A coincidence? I dont belive in it, so i looking for reasons.

So again, i am unwillig to say there is something wrong, but i also unwillig to see a coincidence that the model with near observed sea ice state in Hindcast, produce nearly same spatial pattern and sea ice concentration in September in forecast

PS:
I do test the domains Greenland(as decribed in your Paper) vs. Arctic (70-90N) MPI-ESM-MR and found for 200z Trend-Conditions: JJA in 1979-2016

MPI-ESM-MR
(Arctic:Greenland)
1.00:1.34

NCEP-Reanalysis
1.00:1.73
This would imply that they both do have a stronger trend in z200 on Greenland which is in contrast to CMIP5-mean

PPS: On Tropical domain, MPI-ESM-MR increase (T2m) near double strong as in Observation
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 12, 2017, 09:51:53 PM
-- why the model MPI-ESM-MR can produce it and have one of the best representations in Hindcast of cyrosphere state (Annual-Extent, Trend and Aplitude). --

good question,

my reading of it is that they do not have aerosol-cloud interactions but they do have a strong cloud-effect positive forcing parameter and just happen to under represent tropical upper troposphere temps by about 1K.

in effect, while indirect cloud aerosol interactions are not expressly described, increases in upper troposphere humidity and cooling under aerosol loading and cloud expansion under a reduction in aerosols as well as observed Tropical variability are represented well which happens to work as a good proxy for the interactive effects of high-troposphere aerosols - though again, it appears to be an artifact of the model and not directly aerosol-forced paramaterization.

though this is not strictly expressed in the model description.  it fits.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 13, 2017, 06:02:49 AM
My point exactly.
Rob - you're not making sense.  When they ran the same simulations with and without AGW influence how can that possibly be characterized as not trying to determine the effects of AGW?  That's what Exp-5/6 were about. 

ktonine, you misunderstand Exp-5/6.
These experiments do NOT try to determine the effects of AGW.
They try to determine the effect of 'atmospheric circulation' and specifically the effect of Z200GL (geopotential height over Greenland). Ding et al 2017 uses a regression method to find out how much the other variables (including the most important one : temperature) may have been affected by Z200GL. As a result, the method knocks out 2/3rd of the Arctic temperature trend, effectively assigning it to 'atmospheric circulation' as the cause.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Michael Hauber on April 13, 2017, 06:43:49 AM

If you can show me an ensemble mean ( more than 10 to 20+ realizations) of multiple models forced by anthropogenic forcing ( whatever you like to add in the models, Co2, aerosol, land surface use and ozone etc ) that can well capture the observed circulation change in the past 40 years. I think this would be a good evidence that my argument is wrong. If not, we have to say that a portion of observed circulation change is due to a natural source and this part of natural source can melt sea ice through a dynamical impact rather than the greenhouse effect.
 
Please read our papers in 2014 (fig. 4) and 2017(fig.4) . We checked all available models to do this analysis and we couldn't find a similarity.

(I added emphasis to quotation)

As far as I can understand should the statement be:

The circulation change is due to an unknown cause.  Modelling cannot find a link between Co2 and this circulation change, which is evidence that it is not Co2.  But until this circulation change is better understood it is not really known whether it is purely random natural variation, an alternative external forcing such as aerosols etc, or whether there is an important influence of Co2 on the climate that models cannot yet capture.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on April 13, 2017, 07:09:32 AM

If you can show me an ensemble mean ( more than 10 to 20+ realizations) of multiple models forced by anthropogenic forcing ( whatever you like to add in the models, Co2, aerosol, land surface use and ozone etc ) that can well capture the observed circulation change in the past 40 years. I think this would be a good evidence that my argument is wrong. If not, we have to say that a portion of observed circulation change is due to a natural source and this part of natural source can melt sea ice through a dynamical impact rather than the greenhouse effect.
 
Please read our papers in 2014 (fig. 4) and 2017(fig.4) . We checked all available models to do this analysis and we couldn't find a similarity.

(I added emphasis to quotation)

As far as I can understand should the statement be:

The circulation change is due to an unknown cause.  Modelling cannot find a link between Co2 and this circulation change, which is evidence that it is not Co2.  But until this circulation change is better understood it is not really known whether it is purely random natural variation, an alternative external forcing such as aerosols etc, or whether there is an important influence of Co2 on the climate that models cannot yet capture.
Thanks Michael, good summary of my thinking in better terms than I could articulate.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 13, 2017, 07:19:21 AM
ktonine, you misunderstand Exp-5/6.
These experiments do NOT try to determine the effects of AGW.
They try to determine the effect of 'atmospheric circulation' and specifically the effect of Z200GL (geopotential height over Greenland). Ding et al 2017 uses a regression method to find out how much the other variables (including the most important one : temperature) may have been affected by Z200GL. As a result, the method knocks out 2/3rd of the Arctic temperature trend, effectively assigning it to 'atmospheric circulation' as the cause.

Rob one set has the AGW trend (or most of it) removed - the other does not.  No?  Looking at the difference is a comparison or an attempt to judge the influence of AGW.  Characteriizing it otherwise is incorrect.  Yes, they're looking at the influence on the atmospheric pattern because that's what they judge as significant.  Again, you're just chasing down the same rabbit hole.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 13, 2017, 10:41:42 AM

If you can show me an ensemble mean ( more than 10 to 20+ realizations) of multiple models forced by anthropogenic forcing ( whatever you like to add in the models, Co2, aerosol, land surface use and ozone etc ) that can well capture the observed circulation change in the past 40 years. I think this would be a good evidence that my argument is wrong. If not, we have to say that a portion of observed circulation change is due to a natural source and this part of natural source can melt sea ice through a dynamical impact rather than the greenhouse effect.
 
Please read our papers in 2014 (fig. 4) and 2017(fig.4) . We checked all available models to do this analysis and we couldn't find a similarity.

(I added emphasis to quotation)

As far as I can understand should the statement be:

The circulation change is due to an unknown cause.  Modelling cannot find a link between Co2 and this circulation change, which is evidence that it is not Co2.  But until this circulation change is better understood it is not really known whether it is purely random natural variation, an alternative external forcing such as aerosols etc, or whether there is an important influence of Co2 on the climate that models cannot yet capture.

Hi Michael, thanks for your comment, however it slightly distorts what Dr Ding wrote. Note that Dr Ding does mention various anthropogenic forcings: "CO2, aerosol, land surface use and ozone etc", not just CO2.

If you can show me an ensemble mean ( more than 10 to 20+ realizations) of multiple models forced by anthropogenic forcing ( whatever you like to add in the models, Co2, aerosol, land surface use and ozone etc ) that can well capture the observed circulation change in the past 40 years. I think this would be a good evidence that my argument is wrong.
(emphasis mine)

But this amounts to blaming the CMIP5 model ensemble for not correctly capturing the observed circulation change over the Arctic, something they have not been specifically designed for.
Again, don't blame the models, they are just tools.

And again, there are no "good" or "bad", "right" or "wrong" models. Models can be useful to evidence mechanisms or other phenomena in the chaotic global climate system, and they are an essential tool not only in climate science but in many other areas of human knowledge.
So (imo) it is not a question of finding "better" models here.

Last but not least, I would like to thank Dr. Ding, for taking note of the second part of my question no.1 (*) in one of my previous comments, and for continuing to engage in an open and vigorous discussion of his paper here on ASIF.

* (the full question was:
"1. In the abstract of your 2017 paper, one can read: "Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30-50% of the overall decline in September sea ice since 1979." My question (in two parts) is: how confident are you and your co-authors about these numbers, and what scientific experiment could be made, or physical evidence would be required, if any, to invalidate this claim?")

Dr Ding's most interesting answer is food for thought, and I'll probably spend a few many hours this weekend thinking about it.


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 13, 2017, 10:51:16 AM
Quote
But this amounts to blaming the CMIP5 model ensemble for not correctly capturing the observed circulation change over the Arctic, something they have not been specifically designed for.
Again, don't blame the models, they are just tools.

+1  Although my complaint is the assigning of 'natural variability' to unaccounted for melting.  We know that atmospheric circulation and composition only account for a portion of the melting and that ocean circulation, i.e. warm water incursions, and general warming, as well as ocean (and ice) atmospheric interactions have a major role.

These are all influenced by anthropogenic factors.  And also global circulation changes, as a result of atmospheric chemistry changes and warming.

We are dealing with a badly designed research paradigm.  One that provides no useful information and makes claims not supported but merely conjectured.

   
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 13, 2017, 11:38:19 AM
...
We are dealing with a badly designed research paradigm.  One that provides no useful information and makes claims not supported but merely conjectured.
(emphasis mine)
I couldn't agree more.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 13, 2017, 11:55:12 AM
So, if you would want to tease out the contributions of AGW and natural variation to Arctic sea ice loss, what would your "designed research paradigm" be? How would you go about it?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Cid_Yama on April 13, 2017, 12:27:23 PM
Why would I want to do that and what does that mean?  It is clear that human activities have caused both atmospheric chemical and circulation changes that threaten our very existence.

What IS natural variation after a century and a half of our dramatically changing the chemistry of the atmosphere?

Your question, to me seems meaningless.  There is no longer anything natural about what's going on.

Paintings from the 16th to the 19th century show a sky that was robin egg blue.  It's not anymore.

CO2 levels are beyond anything we have experienced throughout our evolution and may already be doing physiological harm.

What would I be parsing out and why?  Would it provide us with anything useful?

All this paper shows is unaccounted for melting in the various climate models.  Then provides unwarranted conclusions.

We already know a slew of factors affecting the ice that is not included in the climate models.

Explain to me how this paper provides me with any information of value.   

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 13, 2017, 12:40:10 PM
You're mixing up two issues here, namely the science and the societal debate. We've talked about how this research had a high likelihood of being spun, and how that perhaps could've been spun prevented (edit N.). And we've talked about the science. I understand that people don't like how it was spun (neither do I) and that they then try to find issue with the science. That's all understandable, and I'm not even taking issue with that.

But the way you criticize the research, implies that you know how it could've been done better. If not, you are saying that the research shouldn't have been done in the first place. But don't we want to know the respective contributions of AGW and natural variation to Arctic sea ice loss? That's a legitimate and interesting scientific question, right?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 13, 2017, 12:59:51 PM
...
We are dealing with a badly designed research paradigm.  One that provides no useful information and makes claims not supported but merely conjectured.
(emphasis mine)
I couldn't agree more.

Some times science moves forward by posing mere conjectures, for others to prove or disprove....research is not always clean and perfect and accurate....
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: FredBear on April 13, 2017, 01:12:40 PM
I feared the word "Natural" in the Dr Ding paper would become a focus for BAU merchants selling carbon for energy but has this happened? It may be a good attempt find features that are causing ice loss but sadly the "N" word in this particular paper has generated much more heat than light in this forum. There may be factors that can now be watched more closely  .  .   .

I have felt like:-
https://www.youtube.com/watch?v=-myUNjYjhIA (https://www.youtube.com/watch?v=-myUNjYjhIA)
as arguments beyond me whistled by!

Surely the arguments are going to become more & more academic as the  40%+ of anthropogenic factors increasingly tilts the balance against the ice? The coming melt season may well prove to be more interesting  .   .   .   (and provide more useful data?)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: crandles on April 13, 2017, 01:26:42 PM
You're mixing up two issues here, namely the science and the societal debate. We've talked about how this research had a high likelihood of being spun, and how that perhaps could've been spun. And we've talked about the science. I understand that people don't like how it was spun (neither do I) and that they then try to find issue with the science. That's all understandable, and I'm not even taking issue with that.

But the way you criticize the research, implies that you know how it could've been done better. If not, ou are saying that the research shouldn't have been done in the first place. But don't we want to know the respective contributions of AGW and natural variation to Arctic sea ice loss? That's a legitimate and interesting scientific question, right?

+1
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on April 13, 2017, 02:19:57 PM
But the way you criticize the research, implies that you know how it could've been done better. If not, you are saying that the research shouldn't have been done in the first place. But don't we want to know the respective contributions of AGW and natural variation to Arctic sea ice loss? That's a legitimate and interesting scientific question, right?

I can think of better ways to spend our soon to be very limited research dollars.  More satellites would be nice.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 13, 2017, 02:48:58 PM
Why would I want to do that and what does that mean?  It is clear that human activities have caused both atmospheric chemical and circulation changes that threaten our very existence.

What IS natural variation after a century and a half of our dramatically changing the chemistry of the atmosphere?

Your question, to me seems meaningless.  There is no longer anything natural about what's going on.

Paintings from the 16th to the 19th century show a sky that was robin egg blue.  It's not anymore.

CO2 levels are beyond anything we have experienced throughout our evolution and may already be doing physiological harm.

What would I be parsing out and why?  Would it provide us with anything useful?

All this paper shows is unaccounted for melting in the various climate models.  Then provides unwarranted conclusions.

We already know a slew of factors affecting the ice that is not included in the climate models.

Explain to me how this paper provides me with any information of value.

Best post in this entire thread.

Richard hesitated and looked at Rieux:

- Sincerely, tell me your thoughts, do you have the certainty that this is the plague?

- You are not asking the right question. It's not a matter of vocabulary, it's a matter of time.

"Your opinion on the matter," said the Prefect, "would be that, even if it were not plague, the prophylactic measures indicated in cases of plague should, however, be applied.

- If it is absolutely necessary that I have an opinion on the matter, it is indeed this one.

The doctors consulted and Richard finally said,

- So we have to take responsibility for acting as if the disease was the plague.

The formula was warmly approved:

"Is that your opinion, my dear colleague?" asked Richard.

"The wording is indifferent to me," said Rieux. "Let's just say that we should not act as if half the city would not be killed because then it would be."


Albert Camus, The Plague. (1947)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 13, 2017, 03:43:28 PM
That's a great novel by Camus, but the analogy is false. No one is saying there isn't a plague.

Does anyone wonder why climate risk deniers got so little traction out of this? Because they indirectly admit there is a plague.  That's why Arctic sea ice is such an incredible PITA for them. It's the whole reason the ASIB and then this Forum was set up. So, not too much of a worry there.

Which brings us safely back to the science. First of all, no one has ever claimed that all of Arctic sea ice loss was because of AGW (that's the strawman climate risk deniers use). For scientists and those in the know, it's clear that there may be a natural component causing part of the loss. If there is a natural component, I think it would be extremely useful to know about it. We're not finding out if no one is researching it.

Secondly, it's not just that we want to know this, so we can pinpoint when the Arctic will go ice-free. This is irrelevant, as it is almost certain that is going to happen in 0-15 years from now. We need to increase our understanding of how it all works, and what the contributions from AGW and natural variation (if any) are, if we want to have a good understanding while monitoring the comeback of Arctic sea ice. Either because of some geoengineering, or because we manage to quickly reduce CO2 emissions and then take it out of the atmosphere.

So, attack the science because there are flaws. That's how science advances.

But don't attack the science because you perceive it as some social threat. That energy is better spent elsewhere. In your garden, for instance. And in efforts to change the system.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 13, 2017, 03:51:57 PM
So, if you would want to tease out the contributions of AGW and natural variation to Arctic sea ice loss, what would your "designed research paradigm" be? How would you go about it?

why would you intentionally attempt to assign a value of 'natural variability' to a dynamic system that is in the process of catastrophic collapse?  Is it because the collapse is not what you expected?

This is hubris. 

The aerosol cooling component in the Arctic is extremely well documented, as is the poor representation by current models of the full effects of aerosols on both global scales and in the Arctic.  With the clear understanding of the CMIP5 ensemble understating these impacts to the Arctic.  We should expect a more rapid loss of sea ice than the models predict.

http://www.nature.com/ngeo/journal/v9/n4/full/ngeo2673.html (http://www.nature.com/ngeo/journal/v9/n4/full/ngeo2673.html)

Amplification of Arctic warming by past air pollution reductions in Europe

Quote
Here we present simulations with an Earth system model with comprehensive aerosol physics and chemistry that show that the sulfate aerosol reductions in Europe since 1980 can potentially explain a significant fraction of Arctic warming over that period. Specifically, the Arctic region receives an additional 0.3 W m−2 of energy, and warms by 0.5 °C on annual average in simulations with declining European sulfur
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 13, 2017, 04:05:12 PM
So, if you would want to tease out the contributions of AGW and natural variation to Arctic sea ice loss, what would your "designed research paradigm" be? How would you go about it?

why would you intentionally attempt to assign a value of 'natural variability' to a dynamic system that is in the process of catastrophic collapse?  Is it because the collapse is not what you expected?

The atmospheric and ocean dynamic system is in no threat of collapse. Biosphere as we know it is. Understanding the internal variability (sans forcing) of the system, helps you improve your understanding to its detailed response to forcings. Then you can more accurately model scenarios and responses. And if it comes to geoengineering, I would like to be able to predict what it might do as accurately as possible.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 13, 2017, 04:18:08 PM
... if we want to have a good understanding while monitoring the comeback of Arctic sea ice. ...
:o
You are joking, right?
We are already committed to the complete and irreversible (on a human time scale) disappearance year round of Arctic sea ice.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 13, 2017, 04:23:32 PM
... if we want to have a good understanding while monitoring the comeback of Arctic sea ice. ...
:o
You are joking, right?
We are already committed to the complete and irreversible (on a human time scale) disappearance year round of Arctic sea ice.

That kind of makes me want to shut down the blog and forum, and build a big bunker. And so the narrative I tell myself (and hopefully others once I get back to blogging) is that what we need to fight for, is getting Arctic sea ice back after we lose it. Preferably prevent it from going ice-free all year round.

Quote
why would you intentionally attempt to assign a value of 'natural variability' to a dynamic system that is in the process of catastrophic collapse?  Is it because the collapse is not what you expected?

If it is all collapsing, there's not much sense in thinking about what the best way to do research is. Or post on a forum. And what I've said in reply to AndrewB.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 13, 2017, 04:28:39 PM
But the way you criticize the research, implies that you know how it could've been done better. If not, you are saying that the research shouldn't have been done in the first place. But don't we want to know the respective contributions of AGW and natural variation to Arctic sea ice loss? That's a legitimate and interesting scientific question, right?

I can think of better ways to spend our soon to be very limited research dollars.  More satellites would be nice.

Satellites are expensive. Modelturbation is cheap.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 13, 2017, 05:17:27 PM
That kind of makes me want to shut down the blog and forum, and build a big bunker. And so the narrative I tell myself (and hopefully others once I get back to blogging) is that what we need to fight for, is getting Arctic sea ice back after we lose it. Preferably prevent it from going ice-free all year round.
Neven,
I would suggest then you re-read The Plague, just to see how various characters react to the situation.

We can't "fight [to get] the Arctic sea ice back". There is no technology to do so, and the scale of the problem vastly exceeds the capabilities of what humankind can achieve, even with a global wartime effort.
What we can do is reduce GHG emissions as fast as possible, and to do so we need to push for public policies that reduce our reliance on fossil fuels. There is no extinction threat here, but for sure hundreds of millions of human beings will suffer and possibly tens of millions will die, if we don't act as quickly as possible. It is a question of time, as Docteur Rieux says in The Plague.

Now, the question of what exact percentage (if any) of atmospheric circulation changes over the Arctic in June July August over the period 1979-2014 can be attributed to "natural climate variability" is purely academic, and at this point in the unfolding global warming catastrophe, a distraction, and a waste of time.
Similarly, calling the disappearance of 75% of sea ice volume a "collapse" or "sea ice changes due to natural variability intrinsic in atmospheric circulation" is just a question of words, and changes absolutely nothing to the reality of what is happening.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: nukefix on April 13, 2017, 05:32:25 PM
Satellites are expensive. Modelturbation is cheap.
All models are wrong, but some are useful. Meanwhile satellites...are needed to constrain the models. And even with well constrained models extrapolations into the future are problematic.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on April 13, 2017, 05:45:23 PM
... if we want to have a good understanding while monitoring the comeback of Arctic sea ice. ...
:o
You are joking, right?
We are already committed to the complete and irreversible (on a human time scale) disappearance year round of Arctic sea ice.

That kind of makes me want to shut down the blog and forum, and build a big bunker. And so the narrative I tell myself (and hopefully others once I get back to blogging) is that what we need to fight for, is getting Arctic sea ice back after we lose it. Preferably prevent it from going ice-free all year round.

Quote
why would you intentionally attempt to assign a value of 'natural variability' to a dynamic system that is in the process of catastrophic collapse?  Is it because the collapse is not what you expected?

If it is all collapsing, there's not much sense in thinking about what the best way to do research is. Or post on a forum. And what I've said in reply to AndrewB.
Bunkers are attractive but in the long run ineffective.

I appreciate greatly Dr. Ding jumping into our discussion, even as I struggle to fully grasp the nuances of argument. His doing so is the quintessence of good scholarship.

While I generally understand his teams methodology, which in context of process seems sound, I am wrestling with the label "natural variation" to describe "unforced" departure from average.

That's a big bucket, and I'm wondering how much of that is anthropomorphic change outside of the Arctic translating into it. Perhaps, Dr. Ding, you could address that thought?

Last thought to Neven - even if we cannot recover the Arctic as it was,  we still must consider the potential loss of billions of lives due to climate change. That deserves our continued discussion.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 13, 2017, 06:20:02 PM
If natural variability does play such a large role as Ding et al estimate, would it be possible to detect comparably large sea ice losses in the past? Or do we not have good enough data and/or models for such detection?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 13, 2017, 06:28:52 PM
sorry I was unclear, in talking about collapsing systems, I was specifically talking about summer sea ice.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 13, 2017, 07:10:45 PM
If natural variability does play such a large role as Ding et al estimate, would it be possible to detect comparably large sea ice losses in the past? Or do we not have good enough data and/or models for such detection?

I dont think its not that easy, as i make clear in this thread, i have doubts about sperate nat. variability and forcing in this way (because in my opinion the choose of models to use must have a near real world cyrosphere state to make conclusion confident), on the other hand, in real climate, external forcing and internal variability interact with each other. What i want to say is, that thinner ice also could amplifier weather effects or internal inter to decadel variability.

Therefore, in past if ice was thick enough, the impact on extent could be less effective as now, we can see in observation some evidence if we looking at the time and the first Sigma on a running 5y

Here 5y running Sigma1 in Exent for September 1979-2016
http://www.directupload.net/file/d/4690/tk4qsvjl_png.htm (http://www.directupload.net/file/d/4690/tk4qsvjl_png.htm)

We can also watch the weather Pattern, here i use the 500mb geopot for Summer Saison (JJA)
http://www.directupload.net/file/d/4690/cxwxrpya_png.htm (http://www.directupload.net/file/d/4690/cxwxrpya_png.htm)

So well we see that variability in 500mb is not increasing(but correlates) but the variability of extent and if we take them together, we see near the end, there is a disconnect also to see is, that ice is probably leads 500mb geopot untill the disconnect
left: 5y running Sigma 1 of 500mb gepot for JJA on 70-90N)
right: 5y running Sigma 1 of sea ice extent in September

http://www.directupload.net/file/d/4690/gu76bgh3_png.htm (http://www.directupload.net/file/d/4690/gu76bgh3_png.htm)

Under the line:
The very high Sigma1 of the very most past years can not be explain to variability of the weather, so as some Paper has claim it seem likly that thinner ice acting like a amplifier. So long text, but come to a conclusion to your question, i think it have not to be detect in the past.


greets
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 13, 2017, 08:27:00 PM
If natural variability does play such a large role as Ding et al estimate, would it be possible to detect comparably large sea ice losses in the past? Or do we not have good enough data and/or models for such detection?

Datasets for sea ice available here: http://nsidc.org/data/search/#keywords=sea+ice/sortKeys=score,,desc/facetFilters=%257B%257D/pageNumber=1/itemsPerPage=25 (http://nsidc.org/data/search/#keywords=sea+ice/sortKeys=score,,desc/facetFilters=%257B%257D/pageNumber=1/itemsPerPage=25)

I think the earliest data from historical records goes back to 1850. But I doubt very much there is any record, historical or reconstructed from sediments or whatever, of any Arctic sea ice loss comparable to what we have experienced in the last 40 years or so (75% loss in September sea ice volume).

The Eskimo people have lived around the Arctic for the last 3,000 years or so, and their dependence on sea ice is such that we can predict their culture will disappear together with Arctic sea ice, before the end of this century.

I also mentioned a recent paper about the Barnes Ice Cap. It has survived > 2,000 years (ergo, > 2,000 summers) with practically a constant average volume. But now it's bound to disappear within decades. If anything, that is physical evidence that the present warming of the Arctic is totally unprecedented.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 13, 2017, 09:56:44 PM
How about this paper Piron & Pasalodos 2016 (Neven has blogged about it):
https://diablobanquisa.wordpress.com/2016/01/14/new-time-series-september-arctic-sea-ice-extent-1935-2014/

Their fig5 below shows an average year to year variation of a little over 0.5 million km2 (eyeballing their red line) from the decadal mean/trends from 1935-2014. On decadal scale the variation could be about 1 million km2 from the mean over about 70 years of about 7 million km2. Total sea ice extent loss is about 3 million km2 over 1935-2014, assuming 7 million km2 as the baseline. So if 1 millon km2 of that loss would be due to natural variability, then 2 million km2 should be due to global warming. So that would be about 33%. But is 7 million km2 the correct baseline and 70 years the right period? And have cooling aerosols maybe prevented even more melting? And how about volume loss over that period?

I suppose the period should be at least 90 years since the biggest loss happened from 2000-2014, so the data should be extended at least to 1925 to estimate the right baseline, right? And how about natural variability over centuries?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 13, 2017, 10:25:33 PM
Also have a look at fig 8 of Walsh et al 2016:
http://onlinelibrary.wiley.com/doi/10.1111/j.1931-0846.2016.12195.x/full (http://onlinelibrary.wiley.com/doi/10.1111/j.1931-0846.2016.12195.x/full)

It shows maybe 0.5 million km2 decadal variability from 1850-1925 and about 1 million km2 from 1925-2000. So over 150 years the variability is limited and then ice loss grows fast in the last 10-15 years. If the natural ccyle should have gone up then all of the loss should be due to global warming. If part of that loss is due to natural variability, then the cycle should be even longer than 150 years, so we should look back even further. Ding et al didn't do that, so what can they say about natural variability? or maybe I'm missing something?

The natural long term global (and Arctic?) temperature trend was cooling, as far as I know, so sea ice extent should have been increasing, if not for global warming, I would think.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: StopTheApocalypse on April 13, 2017, 10:49:12 PM
It seems to me that the assumption is that if there is not already a well understood mechanism causing demonstrating that SIE loss is caused by AGW, it's assumed to be internal (natural?) variability. Is that more or less correct? If so, it's just another example of scientists being conservative. This is fine, but should be emphasized by the media when being reported.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 13, 2017, 11:01:34 PM
Or we can look at Polyak et al 2010:
https://www.geo.umass.edu/faculty/jbg/Pubs/Polyak%20etal%20seaice%20QSR10%20inpress.pdf (https://www.geo.umass.edu/faculty/jbg/Pubs/Polyak%20etal%20seaice%20QSR10%20inpress.pdf)

See their fig 2a and fig 12 below.

Or fig 3a in Kinnard et al 2011:
http://projects.iq.harvard.edu/files/climate/files/kinnardetal2011.pdf (http://projects.iq.harvard.edu/files/climate/files/kinnardetal2011.pdf)

That last one shows a variability over many centuries of maybe 0.5-1 million km2 around a slightly growing trend a little above 10 million km2. And then a steep drop since 1950 or so of maybe 5 million km2 by now. So at least 80% should be due to AGW, I would guess, if not more or all of it.

Of course we don't know how reliable these data are, but neither do we know this about the models until they can be tested against more reliable data. So this seems the best we have so far. Or not?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: magnamentis on April 13, 2017, 11:41:51 PM
... if we want to have a good understanding while monitoring the comeback of Arctic sea ice. ...
:o
You are joking, right?
We are already committed to the complete and irreversible (on a human time scale) disappearance year round of Arctic sea ice.

That kind of makes me want to shut down the blog and forum, and build a big bunker. And so the narrative I tell myself (and hopefully others once I get back to blogging) is that what we need to fight for, is getting Arctic sea ice back after we lose it. Preferably prevent it from going ice-free all year round.

Quote
why would you intentionally attempt to assign a value of 'natural variability' to a dynamic system that is in the process of catastrophic collapse?  Is it because the collapse is not what you expected?

If it is all collapsing, there's not much sense in thinking about what the best way to do research is. Or post on a forum. And what I've said in reply to AndrewB.

neven in absoluter hochform ( neven in high performance mode LOL ) this thread made my day, keep going.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 14, 2017, 12:39:57 AM

I also mentioned a recent paper about the Barnes Ice Cap. It has survived > 2,000 years (ergo, > 2,000 summers) with practically a constant average volume. But now it's bound to disappear within decades. If anything, that is physical evidence that the present warming of the Arctic is totally unprecedented.

And don't forget the Ellesmere Island ice shelves (http://neven1.typepad.com/blog/2011/09/you-do-it-to-your-shelf-.html) (hat-tip to Judith Curry).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 14, 2017, 02:45:53 AM
Figure 2a. wow thanks Lennart van der Linde I've never seen that before. That paper looks like a must read.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 14, 2017, 06:17:43 AM
ktonine, you misunderstand Exp-5/6.
These experiments do NOT try to determine the effects of AGW.
They try to determine the effect of 'atmospheric circulation' and specifically the effect of Z200GL (geopotential height over Greenland). Ding et al 2017 uses a regression method to find out how much the other variables (including the most important one : temperature) may have been affected by Z200GL. As a result, the method knocks out 2/3rd of the Arctic temperature trend, effectively assigning it to 'atmospheric circulation' as the cause.

Rob one set has the AGW trend (or most of it) removed - the other does not.  No?
No, ktonine.
You seem to be pretty hard to convince, but take a look at your own quote from Ding et al 2017 :
Quote
Given a strong correlation between circulation and surface winds, temperature, specific humidity, sea-level pressure, and downwelling long wave radiation in the Arctic,variability and trends in these six variables that are associated with Z200GL are processed and removed from the forcing.
So they teased out the influence of Z200GL, and NOT "the AGW trend".

If you still believe that Exp.5/6 were about AGW trend, please state it as a question. Qinghua Ding mentioned that he has some time this weekend, and he may be able to answer you better than I did.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 14, 2017, 06:37:56 AM
So, if you would want to tease out the contributions of AGW and natural variation to Arctic sea ice loss, what would your "designed research paradigm" be? How would you go about it?

I love it. Thank you Neven.

In general, it is very hard to tease out the contributions of AGW and natural variability to Arctic sea ice loss. As my teacher told me a long time ago : If it were easy, I would have done it myself.

However, Ding et al 2017 DOES provide a tool that we can use to 'tease out' particular variables out of a set of correlated variables.
They did it with this formula, where they 'teased out' the influence of Z200GL (the geopotential height over Greenland) :

B(x, y, t) = β(x, y) × Z200 GL (t)

Here, note that Z200 GL (t) is a scalar time-dependent variable.
Instead of Z200 GL (t) we may be able to 'tease out' the AGW influence using this very same method, but instead of Z200 GL we can insert another scalar time-dependent variable, like the global warming variable LOTI :
https://data.giss.nasa.gov/gistemp/graphs/

We would just need to calculate :

B(x, y, t) = β(x, y) × LOTI (t)

and of course, need to re-calculate β(x, y) for each grid point and each variable against LOTI.
Fairly trivial to do if you have the data set up.

After that, we could re-run Exp.6. and see how sea ice is affected (by LOTI).

What we would have done in that case, would be to 'tease out' AGW out of the Arctic variables, and that would be a start (to see what AGW influence is on Arctic sea ice).

Of course, this method assumes that there is no "Arctic amplification" during the summer months.
But it would be a start...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 14, 2017, 10:03:10 AM
So, if you would want to tease out the contributions of AGW and natural variation to Arctic sea ice loss, what would your "designed research paradigm" be? How would you go about it?
...
However, Ding et al 2017 DOES provide a tool that we can use to 'tease out' particular variables out of a set of correlated variables.
...

After that, we could re-run Exp.6. and see how sea ice is affected (by LOTI).

What we would have done in that case, would be to 'tease out' AGW out of the Arctic variables, and that would be a start (to see what AGW influence is on Arctic sea ice).
...

Hi Rob,
The problem is, you are using the same method as Ding et al 2017, with the same uncertainties associated with the model used (POP2+CICE4) and with similar uncertainties with respect to the data and the basic assumptions.
In the end, you would almost certainly be able to make a similar claim as the one that is found in the Ding et al 2017 paper, which if we really account for the uncertainties in the entire "experiment", would read like:
“Global warming may be responsible (with 95% confidence) for about -40 to +120% of the overall decline in September sea ice since 1979.”

Totally meaningless...

A methodology is inherently flawed when the result can mean something and exactly its opposite, which is the case with the methodology used in the Ding et al 2017 paper.

There is a much "cleaner" method to determine the influence of cumulative CO2 emissions on average Arctic sea ice volume, it's the simple, mathematically correct and obvious linear correlation found in the Notz and Stroeve 2016 paper. Which attributes 100% of the decline in Arctic sea ice volume to cumulative CO2 emissions, with a simple causality chain, and with high statistical confidence.

Ding et al 2017 went around with a very complicated methodology that hides its inherent flaws because they wanted to reach a predetermined conclusion, extremely similar to the conclusion they had already reached in the Ding et al 2014 paper, about natural variability.

But all this is absolutely irrelevant and a waste of time, and time now is of the essence. What really matters these days is what each climate science paper brings to the table for policy makers:
- The Notz and Stroeve 2016 paper clearly underlines the imperative to reduce CO2 emissions from the burning of fossil fuels as quickly as possible. Dr. Notz makes exactly the same point in his COP21 (2015) presentation (see the YouTube video I linked to in one of my previous comments).
- The Ding et al 2017 paper is useless for policy makers concerned with AGW. That is the essence of what Cid_Yama wrote in what I consider is (by far) the best comment in this entire thread.


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 14, 2017, 10:38:20 AM
Satellites are expensive. Modelturbation is cheap.
All models are wrong, but some are useful. Meanwhile satellites...are needed to constrain the models. And even with well constrained models extrapolations into the future are problematic.

Sorry, my phrase was a poor attempt at humor (a "boutade" in French). Satellites are indeed expensive but they are essential to provide us with "hard data" to advance climate science (see for example the Jason 1, 2 and 3 series of satellites that measure SLR with high precision). As for climate models, they are indeed (relatively) inexpensive to develop and use, and they can be extremely useful as tools for climate scientists.

But that is a discussion for another thread.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 14, 2017, 12:18:58 PM
I was just reading this:
https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science

Quote
Ding said his findings in no way minimize the role of anthropogenic warming in melting sea ice. "I don't want people to take the wrong message in our study, that we're not to blame for Arctic warming," said Ding. "The message is that it's more complex than we expected. In the long term, maybe 100 years from now, the Arctic will become ice free in summer because eventually this internal variability will be overwhelmed by anthropogenic forcing."

Dr. Ding, if you're reading this: were you quoted correctly, and if so, what is your assertion based on, or how should it be interpreted?

As far as I know the Arctic could become ice free at the end of summer much earlier than 100 years from now, and ice free during summer probably (or maybe) also quite a bit earlier than 100 years from now.

So what do you mean by "ice free in summer"? Three months of ice free Arctic from June 21st - Sept 21st? Or is one day without ice in those months also ice free in summer?

And what do you mean by "maybe": would that be your best estimate (so should we read "probably"? Or do you mean " maybe as early as 100 years from now"? And does that imply say a 33% chance, or 25%, or 17% or 10%, or even 5%?

In short, what message exactly do you want to give us, the public?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: gerontocrat on April 14, 2017, 12:32:12 PM
Is the phrase "natural variation" itself a cop-out for a blog such as ASIF ? As an over-curious kid I am sure I asked my parents "Why are summers warm and winters cold ?", and did not accept the answer - "Natural variation, my dear". To learn for the first time about the tilt in the axis of the earth, and from that so much else,  was amazing.

So the question I never asked this thread but hoped for the answer is "What is this natural variation of which Dr Ding speaks?". Or should I be posting this in Stupid Questions ?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 14, 2017, 12:34:17 PM
Kaufman et al 2009 showed that the Arctic was cooling over the past 2000 years, until global warming came along:
https://www.skepticalscience.com/past-Arctic-sea-ice-extent.htm (https://www.skepticalscience.com/past-Arctic-sea-ice-extent.htm)

The figure below shows the 10-year running mean and seems to be adapted from and based on figure 3c of the paper itself:
https://www.geo.umass.edu/climate/papers2/Kaufman2009a.pdf (https://www.geo.umass.edu/climate/papers2/Kaufman2009a.pdf)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 14, 2017, 01:01:20 PM
I'm also wondering what a thinning trend means for variation in extent: the thinner the ice gets because of AGW, the larger the potential year-to-year variations in extent, I would guess. So the effects of natural variability could get multiplied by AGW? And how should we seperate those factors from each other?

Also this could imply crossing a treshold/tipping point beyond which the ice cannot easily recover from a large decrease due to natural variability, but this has not been convincingly argued/shown (yet?), if I remember correctly.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 14, 2017, 01:05:44 PM
Is the phrase "natural variation" itself a cop-out for a blog such as ASIF ? As an over-curious kid I am sure I asked my parents "Why are summers warm and winters cold ?", and did not accept the answer - "Natural variation, my dear". To learn for the first time about the tilt in the axis of the earth, and from that so much else,  was amazing.

So the question I never asked this thread but hoped for the answer is "What is this natural variation of which Dr Ding speaks?". Or should I be posting this in Stupid Questions ?

Simple, natural variation is the internal variability of the Earth system ( mostly atmospheric and ocean dynamics ) absent anthropogenic and feedback greenhouse gas emissions....

It includes the Sun, the moon, volcanoes, orbital parameters, etc. which result into patterns and cycles and variability of the trajectory of the atmospheric, ocean and biosphere dynamics, and albedo.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 14, 2017, 01:15:44 PM
I was just reading this:
https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science

Quote
Ding said his findings in no way minimize the role of anthropogenic warming in melting sea ice. "I don't want people to take the wrong message in our study, that we're not to blame for Arctic warming," said Ding. "The message is that it's more complex than we expected. In the long term, maybe 100 years from now, the Arctic will become ice free in summer because eventually this internal variability will be overwhelmed by anthropogenic forcing."

Dr. Ding, if you're reading this: were you quoted correctly, and if so, what is your assertion based on, or how should it be interpreted?

As far as I know the Arctic could become ice free at the end of summer much earlier than 100 years from now, and ice free during summer probably (or maybe) also quite a bit earlier than 100 years from now.

So what do you mean by "ice free in summer"? Three months of ice free Arctic from June 21st - Sept 21st? Or is one day without ice in those months also ice free in summer?

And what do you mean by "maybe": would that be your best estimate (so should we read "probably"? Or do you mean " maybe as early as 100 years from now"? And does that imply say a 33% chance, or 25%, or 17% or 10%, or even 5%?

In short, what message exactly do you want to give us, the public?

Despite Dr. Ding's statement above, the Arctic will be essentially sea ice free at its September minimum probably at some time between 2020 and 2024; and continuously essentially sea ice free for the three months of August, September and October, probably at some time before 2035. And essentially continuously sea ice free year round probably at some time before 2100.

That's what the PIOMAS exponential trendlines in the charts below show.

What I would really like to see Dr. Ding stating is that we need to radically reduce GHG emissions from the burning of fossil fuels ASAP. Then as far as I am concerned he could go back to writing his "natural variability" attribution papers based on model experiments and reanalysis data, and he would never hear one word of criticism from me again.  :-X
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 14, 2017, 01:33:11 PM
AndrewB,

Wow, curve fitting at best, why not using physical stuff, ah would change mind a little bit.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 14, 2017, 02:00:57 PM
AndrewB,

Wow, curve fitting at best, why not using physical stuff, ah would change mind a little bit.

The extremely well designed charts (and exponential trendlines) are from Wipneus, to whom we should all be grateful for making them available and periodically updating them, on his website.

https://sites.google.com/site/arctischepinguin/home
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 14, 2017, 02:15:48 PM
AndrewB,

Wow, curve fitting at best, why not using physical stuff, ah would change mind a little bit.

Eh...hmmm... what "physical" "stuff"?????
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 14, 2017, 02:19:26 PM
I was just reading this:
https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science

Quote
Ding said his findings in no way minimize the role of anthropogenic warming in melting sea ice. "I don't want people to take the wrong message in our study, that we're not to blame for Arctic warming," said Ding. "The message is that it's more complex than we expected. In the long term, maybe 100 years from now, the Arctic will become ice free in summer because eventually this internal variability will be overwhelmed by anthropogenic forcing."

Dr. Ding, if you're reading this: were you quoted correctly, and if so, what is your assertion based on, or how should it be interpreted?

As far as I know the Arctic could become ice free at the end of summer much earlier than 100 years from now, and ice free during summer probably (or maybe) also quite a bit earlier than 100 years from now.

So what do you mean by "ice free in summer"? Three months of ice free Arctic from June 21st - Sept 21st? Or is one day without ice in those months also ice free in summer?

And what do you mean by "maybe": would that be your best estimate (so should we read "probably"? Or do you mean " maybe as early as 100 years from now"? And does that imply say a 33% chance, or 25%, or 17% or 10%, or even 5%?

In short, what message exactly do you want to give us, the public?

This is a good and simple question, much better than the rehash of points already made.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 14, 2017, 02:27:26 PM


Eh...hmmm... what "physical" "stuff"?????

There a lot of variables you can use as a proxie for surface melting, ocean melting and so on, means fitting on physical base
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 14, 2017, 02:40:16 PM


Eh...hmmm... what "physical" "stuff"?????

There a lot of variables you can use as a proxie for surface melting, ocean melting and so on, means fitting on physical base

That is the beauty of simple elegant fits...The Gompetz equation was developed to model the death rate of Humans. Ironic that so far it fits the death rate of ice...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: nukefix on April 14, 2017, 03:06:47 PM

Eh...hmmm... what "physical" "stuff"?????

There a lot of variables you can use as a proxie for surface melting, ocean melting and so on, means fitting on physical base
I suppose one could run 500 instances of climate models for the next 50 years and use each of those runs to force PIOMAS. But the ocean currents would still be out of whack I guess. This shit is hard.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 14, 2017, 05:12:42 PM
unless you ask the right question you will never get the correct answer.

a patent observation, only recently verified by specific models tuned to look at the SO2 emission sea ice impact variation.

Ice free in summer is a colloquial term.  We all know what it means.

100 years is a goddamn joke.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 14, 2017, 05:27:13 PM
Northern hemisphere temperatures should show the same kink since most SO2 emission in the 70's were in the northern hemisphere mid latitudes ( Europe, Americas )
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 14, 2017, 06:51:42 PM
Northern Hemisphere LOTI Nasa GISS with Sulfite emissions

GISS data: https://data.giss.nasa.gov/gistemp/tabledata_v3/NH.Ts+dSST.txt (https://data.giss.nasa.gov/gistemp/tabledata_v3/NH.Ts+dSST.txt)

SO2 data:  http://www.atmos-chem-phys.net/11/1101/2011/acp-11-1101-2011.pdf (http://www.atmos-chem-phys.net/11/1101/2011/acp-11-1101-2011.pdf)

Note that Temperature rise began rapidly not when SO2 emissions were reduced globally but rather when the rate of increase of emissions was stopped.  This reveals significant warming potential locked into the system but not allowed by the rate of change of emissions (increase) and then released through slowdowns in emissions.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on April 15, 2017, 12:04:40 AM
AndrewB, I too am not convinced by the Natural Variation attribution claim for several reasons. However, I think you have taken the criticism way too far, attacking Dr. Ding personally in some of your recent posts. I am sure Dr. ding is an honest researcher with good intentions in mind (even if the paper's method is not to my "liking"), and I am sure he would like to see AGW and CO2 emissions dealt with asap without having to prove himself to you or anyone else. As he is known to be reading this thread and even graciously responding, I am especially ashamed by these attacks and would ask you to avoid such.
In general, I believe your point has been well stated and then overstated, why not give it a rest for a while.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 15, 2017, 08:33:35 AM
Oren,
I agree with your entire post, except for your claim that AndrewB was "attacking Dr. Ding personally in some of your recent posts".

I see no evidence of that.

In fact, AndrewB, even though he disagrees with the method used in Ding et al 2017, has been remarkably civil lately. I even see remarks like this from him :

Quote
Last but not least, I would like to thank Dr. Ding, for taking note of the second part of my question no.1 (*) in one of my previous comments, and for continuing to engage in an open and vigorous discussion of his paper here on ASIF.

and

Quote
Dr Ding's most interesting answer is food for thought, and I'll probably spend a few many hours this weekend thinking about it.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 15, 2017, 09:03:26 AM
So, if you would want to tease out the contributions of AGW and natural variation to Arctic sea ice loss, what would your "designed research paradigm" be? How would you go about it?
...
However, Ding et al 2017 DOES provide a tool that we can use to 'tease out' particular variables out of a set of correlated variables.
...

After that, we could re-run Exp.6. and see how sea ice is affected (by LOTI).

What we would have done in that case, would be to 'tease out' AGW out of the Arctic variables, and that would be a start (to see what AGW influence is on Arctic sea ice).
...

Hi Rob,
The problem is, you are using the same method as Ding et al 2017, with the same uncertainties associated with the model used (POP2+CICE4) and with similar uncertainties with respect to the data and the basic assumptions.
In the end, you would almost certainly be able to make a similar claim as the one that is found in the Ding et al 2017 paper, which if we really account for the uncertainties in the entire "experiment", would read like:
“Global warming may be responsible (with 95% confidence) for about -40 to +120% of the overall decline in September sea ice since 1979.”

Totally meaningless...

Andrew, you can fight the Ding et al 2017 method of 'teasing out' a variable (Z200GL) from a set of correlated variables, or you can embrace it.
I hit my head hard fighting it, so I now embrace it.
If this method can tease out Z200GL, it can also tease out AGW (using the LOTI data).
Even further, we should be able to 'tease out' the dependency of Arctic sea ice decline from the Pacific ocean temperature. A connection that Ding et al 2017 claims as the cause of the Z200GL trend.
That would be interesting experiments, which would tell us more about how solid the claims made in Ding et al 2017 are.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 15, 2017, 09:09:46 AM
Winton 2011 writes:
http://journals.ametsoc.org/doi/full/10.1175/2011JCLI4146.1 (http://journals.ametsoc.org/doi/full/10.1175/2011JCLI4146.1)

"Some studies have focused on the dramatic September ice cover decline (Boé et al. 2009a; Wang and Overland 2009; Zhang 2010). Here, annual average sea ice extent is used in preference to September or other monthly values. Observations and models show that Arctic sea ice anomalies typically persist for only a few months (Blanchard-Wrigglesworth et al. 2011). Additionally, September sea ice cover, the focus of many ice sensitivity studies, is particularly variable and its variability is expected to increase with thinning of the ice (Holland et al. 2006; Goosse et al. 2009; Eisenman 2010). Therefore, considerable variation that is not related to long-term trends can be reduced by using annual averages."

His conclusion:
"substantial natural variability is necessary to reconcile even the most sensitive model with observations. The observational constraint will tighten slowly with time but in the interim it is useful to explore the possibility that the models are not sufficiently sensitive. This has been the theme of several analyses of IPCC AR4 models since the Stroeve et al. (2007) study (Bitz et al. 2011; Boé et al. 2009b). The results here support the importance of this work while holding onto the possibility that, at least for some of the models, the model–observations discrepancy may be due solely to natural variability."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 15, 2017, 09:20:19 AM
AndrewB, also I think your claim of uncertainty in the models (POP2+CICE4) is unwarranted.
Ding et al 2017 shows quite clearly that POP2+CICE4 models, forced with ERA data, reproduce the observed Arctic sea ice trend quite accurately.
Also, the experiments they run (causation Exp.5/6 and attribution Exp.7/8) are "difference" experiments. Apply a different forcing and see what the effect is.
Thus the choice of model is not THAT important, only the relative effect is.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 15, 2017, 09:24:38 AM
AndrewB, I too am not convinced by the Natural Variation attribution claim for several reasons. However, I think you have taken the criticism way too far, attacking Dr. Ding personally in some of your recent posts. I am sure Dr. ding is an honest researcher with good intentions in mind
...
Oren,
Personally, I admire and respect Dr. Ding, and even more so because he has courageously accepted to spare some of his spare time to contribute to this forum. It is quite obvious that Dr. Ding is a highly intelligent person and an accomplished climate scientist, quite confident in his area of expertise. And his courage to defend his paper publicly tells highly of his character.
I hope he takes my vehement criticism of the Ding et al 2017 paper (assumptions, methodology and conclusion) as a personal compliment, and not as a personal insult.

About frequently restating my points: you are absolutely correct. I apologize, and I'll cease posting in this thread unless solicited to do otherwise.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on April 15, 2017, 09:39:07 AM
Well said, AndrewB. I stand corrected.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 15, 2017, 10:18:27 AM
IPCC AR5 WG1 ch12 on Long-term Arctic sea ice decline:
http://www.climatechange2013.org/images/report/WG1AR5_Chapter12_FINAL.pdf (http://www.climatechange2013.org/images/report/WG1AR5_Chapter12_FINAL.pdf)

"In the NH, in accordance with CMIP3 results, the absolute rate of decrease of the CMIP5 multi-model mean sea ice areal coverage is greatest in September. The reduction in sea ice extent between the time periods 1986–2005 and 2081–2100 for the CMIP5 multi-model average ranges from 8% for RCP2.6 to 34% for RCP8.5 in February and from 43% for RCP2.6 to 94% for RCP8.5 in September. Medium confidence is attached to these values as projections of sea ice extent decline in the real world due to errors in the simulation of present-day sea ice extent (mean and trends—see Section 9.4.3) and because of the large spread of model responses. About 90% of the available CMIP5 models reach nearly ice-free conditions (sea ice extent less than 1 × 10^6 km2 for at least 5 consecutive years) during September in the Arctic before 2100 under RCP8.5 (about 45% under RCP4.5). By the end of the 21st century, the decrease in multi-model mean sea ice volume ranges from 29% for RCP2.6 to 73% for RCP8.5 in February and from 54% for RCP2.6 to 96% for RCP8.5 in September. Medium confidence is attached to these values as projections of the real world sea ice volume. In February, these percentages are much higher than the corresponding ones for sea ice extent, which is indicative of a substantial sea ice thinning.

A frequent criticism of the CMIP3 models is that, as a group, they strongly underestimate the rapid decline in summer Arctic sea ice extent observed during the past few decades (e.g., Stroeve et al., 2007; Winton, 2011), which suggests that the CMIP3 projections of summer Arctic sea ice areal coverage might be too conservative. As shown in Section 9.4.3 and Figure 12.28b, the magnitude of the CMIP5 multi-model mean trend in September Arctic sea ice extent over the satellite era is more consistent with, but still underestimates, the observed one (see also Massonnet et al., 2012; Stroeve et al., 2012; Wang and Overland, 2012; Overland and Wang, 2013). Owing to the shortness of the observational record, it is difficult to ascertain the relative influence of natural variability on this trend. This hinders the comparison between modelled and observed trends, and hence the estimate of the sensitivity of the September Arctic sea ice extent to global surface temperature change (i.e., the decrease in sea ice extent per degree global warming) (Kay et al., 2011; Winton, 2011; Mahlstein and Knutti, 2012). This sensitivity may be crucial for determining future sea ice losses. Indeed, a clear relationship exists at longer than decadal time scales in climate change simulations between the annual mean or September mean Arctic sea ice extent and the annual mean global surface temperature change for ice extents larger than ~1 × 10^6 km2 (e.g., Ridley et al., 2007; Zhang, 2010b; NRC, 2011; Winton, 2011; Mahlstein and Knutti, 2012). This relationship is illustrated in Figure 12.30 for both CMIP3 and CMIP5 models. From this figure, it can be seen that the sea ice sensitivity varies significantly from model to model and is generally larger and in better agreement among models in CMIP5...

Today, the optimal approach for constraining sea ice projections from climate models is unclear, although one notes that these methods should have a credible underlying physical basis in order to increase confidence in their results (see Section 12.2). In addition, they should account for the potentially large imprint of natural variability on both observations and model simulations when these two sources of information are to be compared (see Section 9.8.3). This latter point is particularly critical if the past sea ice trend or sensitivity is used in performance metrics given the relatively short observational period (Kay et al., 2011; Overland et al., 2011; Mahlstein and Knutti, 2012; Massonnet et al., 2012; Stroeve et al., 2012)....

[V]arious methods all suggest a faster rate of summer Arctic sea ice decline than the multi-model mean. Although they individually provide a reduced range for the year of near disappearance of the September Arctic sea ice compared to the original CMIP3/CMIP5 multi-model ensemble, they lead to different timings (Overland and Wang, 2013). Consequently, the time interval obtained when combining all these studies remains wide: 2020–2100+ (2100+ = not before 2100) for the SRES A1B scenario and RCP4.5 (Stroeve et al., 2007, 2012; Boé et al., 2009b; Wang and Overland, 2009, 2012; Zhang, 2010b; Massonnet et al., 2012) and 2020–2060 for RCP8.5 (Massonnet et al., 2012; Wang and Overland, 2012). The method proposed by Massonnet et al. (2012) is applied here to the full set of models that provided the CMIP5 database with sea ice output. The natural variability of each of the four diagnostics shown in Figure 12.31a–d is first estimated by averaging over all available models with more than one ensemble member the diagnostic standard deviations derived from the model ensemble members. Then, for each model, a ±2 standard deviation interval is constructed around the ensemble mean or single realization of the diagnostic considered. A model is retained if, for each diagnostic, either this interval overlaps a ±20% interval around the observed/reanalysed value of the diagnostic or at least one ensemble member from that model gives a value for the diagnostic that falls within ±20% of the observational/reanalysed data. The outcome is displayed in Figure 12.31e for RCP8.5. Among the five selected models (ACCESS1.0, ACCESS1.3, GFDL-CM3, IPSL-CM5A-MR, MPI-ESM-MR), four project a nearly ice-free Arctic Ocean in September before 2050 (2080) for RCP8.5 (RCP4.5), the earliest and latest years of near disappearance of the sea ice pack being about 2040 and about 2060 (about 2040 and 2100+), respectively. It should be mentioned that Maslowski et al. (2012) projected that it would take only until about 2016 to reach a nearly ice-free Arctic Ocean in summer, based on a linear extrapolation into the future of the recent sea ice volume trend from a hindcast simulation conducted with a regional model of the Arctic sea ice–ocean system. However, such an extrapolation approach is problematic as it ignores the negative feedbacks that can occur when the sea ice cover becomes thin (e.g., Bitz and Roe, 2004; Notz, 2009) and neglects the effect of year-to-year or longer-term variability (Overland and Wang, 2013). Mahlstein and Knutti (2012) encompassed the dependence of sea ice projections on the forcing scenario by determining the annual mean global surface warming threshold for nearly ice-free conditions in September. Their best estimate of ~2°C above the present derived from both CMIP3 models and observations is consistent with the 1.6 to 2.1°C range (mean value: 1.9°C) obtained from the CMIP5 model subset shown in Figure 12.31e (see also Figure 12.30b). The reduction in September Arctic sea ice extent by the end of the 21st century, averaged over this subset of models, ranges from 56% for RCP2.6 to 100% for RCP8.5. In light of all these results, it is very likely that the Arctic sea ice cover will continue to shrink and thin all year round during the 21st century as the annual mean global surface temperature rises. It is also likely that the Arctic Ocean will become nearly ice-free in September before the middle of the century for high GHG emissions such as those corresponding to RCP8.5 (medium confidence)."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 15, 2017, 11:05:24 AM
Thinning causes more thinning, is my interpretation of Bushuk et al 2017, Summer Enhancement of Arctic Sea Ice Volume Anomalies in the September-Ice Zone:
http://cerfacs.fr/wp-content/uploads/2017/03/GlobC-Article-Msadek-Summer-Mars-2017.pdf (http://cerfacs.fr/wp-content/uploads/2017/03/GlobC-Article-Msadek-Summer-Mars-2017.pdf)

"the size of the summer volume anomaly enhancement increases monotonically with the size of the initial volume anomaly, indicating that this phenomenon is always present but most significant in large anomaly years."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 15, 2017, 11:59:02 AM
Livina & Lenton 2013 on potential Arctic sea ice tipping points:
http://www.the-cryosphere.net/7/275/2013/tc-7-275-2013.pdf (http://www.the-cryosphere.net/7/275/2013/tc-7-275-2013.pdf)

"there has been an abrupt and persistent jump in the amplitude of the seasonal cycle of Arctic sea-ice cover in 2007 (Ditlevsen, 2012), but the underlying causal mechanism remains uncertain. We describe this as a (non-bifurcation) “tipping point”, because it involved an abrupt, qualitative change in the sea-ice dynamics, without any evidence for a large forcing perturbation; i.e. the abruptness resides in the internal dynamics of the Arctic climate system."

And Serreze 2011:
http://www.nature.com.sci-hub.cc/nature/journal/v471/n7336/full/471047a.html (http://www.nature.com.sci-hub.cc/nature/journal/v471/n7336/full/471047a.html)

"with ice-free summers, the ocean picks up a great deal of extra heat, delaying autumn ice growth. If there was a tipping point, this summer heat gain would lead to ice cover the following spring being thin enough to completely melt out over the following summer. Instead, so much ocean heat is lost during the darkness of the polar winter that enough ice grows to survive the next summer’s melt."

Will it? Or will Arctic amplication feedbacks cause much of this extra heat uptake to stay in the Arctic? How large will this amplification be?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 15, 2017, 12:46:26 PM
Pithan & Mauritsen 2014 on Arctic amplification:
http://www.nature.com.sci-hub.cc/ngeo/journal/v7/n3/full/ngeo2071.html (http://www.nature.com.sci-hub.cc/ngeo/journal/v7/n3/full/ngeo2071.html)

"Besides quantifying the different contributions to Arctic amplification in the ensemble mean, it is valuable to understand why models differ in their degree of Arctic amplification. Our analysis shows that intermodel spread in Arctic warming is dominated by the spread in local feedback mechanisms, not meridional transport changes (Fig. 3). Changes in atmospheric heat transport dampen intermodel spread because they are more positive in models with little Arctic warming. This is consistent with results from an energy balance model used to reconstruct warming and transport changes in the Coupled Model Intercomparison Project Phase 3 (CMIP3; ref. 28). In the ensemble mean, atmospheric heat transport does contribute to Arctic amplification by enhancing Arctic and reducing tropical warming (Fig. 2a). Contrary to physical intuition, poleward atmospheric energy transport does not scale with themeridional temperature gradient within individual models, but increases in most models despite a reduction in the Equator-to-pole temperature gradient. Increasing latent energy transports overcompensating the decrease of dry static energy transport have been shown to cause such behaviour of climate models. Changes in ocean transport and ocean heat uptake are not correlated with total Arctic warming across different models.
To develop confidence in model projections of future Arctic warming, it is necessary to quantitatively understand the role of different physical mechanisms for Arctic amplification. Contrary to a widespread assumption, temperature feedbacks are the most important contributors to Arctic amplification in contemporary climate models. The surface albedo feedback is the second main contributor, whereas other suggested drivers of Arctic amplification either play minor roles or even oppose Arctic amplification in the ensemble mean."

An older synthesis on Arctic amplification by Serreze & Barry 2011:
http://www.sciencedirect.com.sci-hub.cc/science/article/pii/S0921818111000397 (http://www.sciencedirect.com.sci-hub.cc/science/article/pii/S0921818111000397)

"The degree of Arctic amplification, assessed as the ratio in the annual mean trend for the region 70–90°N to the trend for the globe as a whole, was 2.9 for the 1970–2008 period, compared with 6.9 for 1910–1940. For winter the ratios for the two periods, respectively, were 2.9 and 12.5, compared to 3.6 and 5.7, respectively, for summer. Corresponding ratios during the cooling period from 1940 to 1970 reached 16.7 for autumn and 16.0 for spring (stronger cooling in the Arctic), with an annual value of 12.5. More recently, Bekryaev et al. (2010) document a northern high-latitude (for land stations north of 59°N) warming rate of 1.36 °C per century for the period 1875–2008, almost twice as strong as the Northern Hemisphere trend (0.79 °C per century),with an even stronger warming rate for the last decade (1.35 °C/decade). Their study included many sites along the Arctic Ocean coast. Fig. 3 shows the annual and seasonal temperature time series from that study.
Surprisingly, apart from the effort by Johannessen et al. (2004), none of the studies discussed above specifically examined the Arctic Ocean, where the strongest Arctic amplification is projected to occur. While coastal sites certainly provide some information as to conditions over the ocean (the Arctic Ocean warming seen in Fig. 2 is strongly influenced by interpolation from coastal stations), a fuller picture requires the use of gridded fields from satellite retrievals or atmospheric reanalyses.
Atmospheric reanalyses provide long time series of atmospheric and surface conditions through data assimilation techniques that blend observations with short-term forecasts from a numerical weather prediction model. Time series from atmospheric reanalyses are standard climate research tools.
Serreze et al. (2009) examined the evolution of temperatures over the Arctic Ocean from 1979 to 2007 using data from two different atmospheric reanalyses. Anomalies were computed with respect to the period 1979–2007. Starting in the late 1990s, surface air temperature anomalies over the Arctic Ocean were seen to turn positive in autumn, growing in subsequent years, and building into winter. Development of the autumn warming pattern was found to align with the observed reduction in September sea ice extent, with the temperature anomalies strengthening from the lower troposphere to the surface. The recent autumn warming was found to be stronger over the Arctic Ocean than over Arctic land areas and lower latitudes. No enhanced surface warming signal was found in summer.
Screen and Simmonds (2010a) examined temperature trends from 1989 to 2008 using output from ERA-Interim, the newest reanalysis from the European Centre for Medium Range Weather Forecasts. They confirmed that the strongest recent warming lies over the Arctic Ocean, most pronounced in autumn and winter, and strongly allied with the observed downward trend in September sea ice extent."

Hind et al 2016:
https://www.nature.com/articles/srep30469 (https://www.nature.com/articles/srep30469)

"Uncertainty in the estimated range of the Arctic amplification factor using the latest global climate models and climate forcing scenarios is expanded upon and shown to be greater than previously demonstrated for future climate projections, particularly using forcing scenarios with lower concentrations of greenhouse gases...

Figure 2 shows the multi-model mean Arctic (orange/yellow) and global (red) temperature changes projected for the period 2081–2100 in contrast with those simulated for 1986–2005 using the four RCP scenarios. The 90% confidence intervals for the spread of Arctic and global temperatures are presented here as provided in Table 12.2 of IPCC AR5 and are essentially very similar for all RCP forcing scenarios. Here, we apply the Fieller method in an attempt to give representative confidence intervals at a 90% significance level for projected Arctic amplification using the Ratio of Means approach, based on the model spread for each RCP forcing scenario (black in Fig. 2). The RCP4.5 and RCP6 simulated future scenarios show a similar uncertainty in the Arctic amplification factor, with potential values ranging from approximately 1.2–3.8 at a 90% significance level (second and third columns in Fig. 2), whereas the RCP8.5 scenario has a somewhat smaller uncertainty, ranging from 1.5–3 (fourth column in Fig. 2). On the other hand, for the RCP2.6 simulated future scenarios an Arctic amplification factor of less than 1 or even negative values are quite possible. In other words, the Arctic region may be able to undergo temperature changes in opposition to the direction of any global changes if the global radiative forcing follows the RCP2.6 pathway. It generally seems as though the uncertainty bounds calculated for future projected Arctic amplification factors indicate that higher numbered RCP forcing experiments (analogous to higher greenhouse gas concentrations) show less uncertainty than the lower RCP experiments. This is perhaps not an unexpected result given that higher greenhouse gas forcings would be expected to increasingly overcome differences in the physical models and internal climate variability."
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: gerontocrat on April 15, 2017, 01:01:25 PM
Is the phrase "natural variation" itself a cop-out for a blog such as ASIF ? As an over-curious kid I am sure I asked my parents "Why are summers warm and winters cold ?", and did not accept the answer - "Natural variation, my dear". To learn for the first time about the tilt in the axis of the earth, and from that so much else,  was amazing.

So the question I never asked this thread but hoped for the answer is "What is this natural variation of which Dr Ding speaks?". Or should I be posting this in Stupid Questions ?

Simple, natural variation is the internal variability of the Earth system ( mostly atmospheric and ocean dynamics ) absent anthropogenic and feedback greenhouse gas emissions....

It includes the Sun, the moon, volcanoes, orbital parameters, etc. which result into patterns and cycles and variability of the trajectory of the atmospheric, ocean and biosphere dynamics, and albedo.

Hullo Doc,

Thanks for the list. BUT (there is always a but)
that is like a climate sceptic/denier asking me "What causes AGW ?", and me answering "CO2". CO2 is what, but what is missing is - what changed - ,   and  - how  did that change the temperature of the biosphere -. I am a non-scientist but I do  basically get the story.

So I ask again, "What changed and how did it cause the Natural Variation of which Dr Ding speaks?"

Help
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Andreas T on April 15, 2017, 01:49:07 PM
Without claiming that this is the definition of "natural variations" used by Dr Ding, I think that natural influences which are outside the average conditions on planet earth don't count as variations but as drivers. So changes in output from the sun, earth orbit and axis orientation, or volcanoes count as drivers, inputs into the climate system. Internal variations are changes which occur if all external inputs remain the same. Because there are so many feedbacks in the system fluctuations in, say sea surface temperature distribution and cloud distribution can reinforce each other (el nino is a prime example) in a way which doesn't average out by making one part of the globe warmer while another colder. El nino of course does of course move energy from a reservoir (sea water) into the atmosphere so has a time span and frequency which is limited by how quickly this reservoir is replenished. I believe such variations can also change the amount of energy which is taken up from the sun but again there are limitations on how much and for how long. Such variations do occur in climate models  as part of the interdependent processes which they describe mathematically.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 15, 2017, 03:33:56 PM
Pithan & Mauritsen 2014 on Arctic amplification:
http://www.nature.com.sci-hub.cc/ngeo/journal/v7/n3/full/ngeo2071.html (http://www.nature.com.sci-hub.cc/ngeo/journal/v7/n3/full/ngeo2071.html)

(1) Changes in atmospheric heat transport dampen intermodel spread because they are more positive in models with little Arctic warming. This is consistent with results from an energy balance model used to reconstruct warming and transport changes in the Coupled Model Intercomparison Project Phase 3

(2) In the ensemble mean, atmospheric heat transport does contribute to Arctic amplification by enhancing Arctic and reducing tropical warming (Fig. 2a). Contrary to physical intuition, poleward atmospheric energy transport does not scale with the meridional temperature gradient within individual models, but increases in most models despite a reduction in the Equator-to-pole temperature gradient.

Hind et al 2016:
https://www.nature.com/articles/srep30469 (https://www.nature.com/articles/srep30469)

(3) "Uncertainty in the estimated range of the Arctic amplification factor using the latest global climate models and climate forcing scenarios is expanded upon and shown to be greater than previously demonstrated for future climate projections, particularly using forcing scenarios with lower concentrations of greenhouse gases...

On the other hand, for the RCP2.6 simulated future scenarios an Arctic amplification factor of less than 1 or even negative values are quite possible. In other words, the Arctic region may be able to undergo temperature changes in opposition to the direction of any global changes if the global radiative forcing follows the RCP2.6 pathway. It generally seems as though the uncertainty bounds calculated for future projected Arctic amplification factors indicate that higher numbered RCP forcing experiments (analogous to higher greenhouse gas concentrations) show less uncertainty than the lower RCP experiments. This is perhaps not an unexpected result given that higher greenhouse gas forcings would be expected to increasingly overcome differences in the physical models and internal climate variability."

(1) models with greater arctic amplification result in lower amounts of mid-latitude latent heat intrusion, models with lower arctic amplification result in higher amounts.  this is because the models expect (are designed to show) atmospheric circulation changes as a result of the  temperature gradient changes produced by a globally averaged forcing and regional (but slow) feedbacks.

(2) In the model mean, the primary force for meridional transport is the temperature gradient, however other circulation changes (feedbacks) bias the mean somewhat so that the amount is slightly greater than the rate of change of the meridional temperature gradient (not scaled).

(3) These results show that the model mean is dominated by GCMs that do not allow for tropical anthropogenic aerosol emission reductions to significantly increase regional Tropopause heights, with increased regional water vapor and lapse rate feedbacks.  The resulting changes in the Tropic geopotential height gradient will produce rapid expansions of the ITCZ, a significant expansion of the Hadley Cell, the greatly increased export of mid-altitude water vapor pulses in the form of atmospheric rivers, the strengthening of (slowing/standing - even short reversal!) Rossby wave activity (due to extreme upper latitude blocking events) that will eventually result in tropical wave/pulse formations that are unprecedented in scope and scale since the early Pliocene.

---  This makes me think that it is time to do a more rigorous  means testing of the climate models as qualification for inclusion in the CMIP6 and drop about 1/2 of them from the ensemble --- as harsh as this would be to the people who have worked incredibly hard on them, we simply cannot let these poor performers continue to bias the ensemble results anymore.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 15, 2017, 05:02:07 PM
jai mitchell  +1

I've been meaning to say this for a while, and this is offtopic, but your coal/aerosols/sst argument is a courageous one. You are saying that shutting down Coal plants causes short term global warming.  I bet you get a lot of flak for that.

When you first started to state that point, I was suspicious of you because it sounded like a very convenient argument for a climate change denier to take advantage of. But then as you refined the argument and presented more and more evidence I realized that my suspicions of your argument  were nothing but my own personal bias. You are probably right and your argument is very important if coal is going to be phased out.

For example phasing out coal plants during warm cycles of the planet will compound the problems of the warming. Closing them during cool earth cycles will reduce the impact of the short term warming at the cost of maintaining the Earth at a higher temperatures for longer.

This might be an important consideration that is impossible to talk about because of the nature of the debate.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 15, 2017, 10:58:34 PM
Hi everyone,

I have no time to read all these threads posted in the past week. So I just started with some points I really want to make first.
 
I think the main reason that someone here don't believe that there is a natural factor to drive the sea ice change is that sea ice only showed a decline trend recently over the past 1000 years ( I remember AndrewB showed some September sea ice curves from some datasets ).

But based on what I learned from these data and literatures, I don't think this is 100% correct. I think it is very likely that there was a very low frequency internal mode ( or a random thing)  that had caused another early warming in the Arctic around 1930s-1940s.

You can find a lot of evidence to support the existence of this early warming event in and around the Arctic, especially over Greenland. ( that is why we used Z200 over there as the index in Ding et al 2017. I will say more about this for Rob) 

 http://onlinelibrary.wiley.com/doi/10.1029/2006GL026510/abstract (http://onlinelibrary.wiley.com/doi/10.1029/2006GL026510/abstract)

please go to this website and check all available surface temperature in the past 100 years over some stations in the high latitudes

https://data.giss.nasa.gov/gistemp/station_data/ (https://data.giss.nasa.gov/gistemp/station_data/)

I also checked all these old sea ice reconstruction data from month to month before 1950s. I think they used a climatology of September from some periods later for all September sea ice before 1950s or 60s. As I know, old sea ice data/charts only recorded sea ice information from April to Aug.  I can plot some old ice data later. you will see what I mean here.

In my view, our understanding of September sea ice variability before 1950s or 60s is very limited because of this data limitation.

if you check old sea ice chart ( I add it as an attachment, I am not sure whether you can see it at the bottom of my post)  in 1938/Aug, you can see a pretty bad sea ice melting in that year. So we should expect a worse melting in 1938/Sep but all sea ice reconstructions in September don't show this because data uses a climatology in September.

 In 1940s and 1950s, due to WW2 and the Cold war, there were no reliable sea ice information so we don't know the real situation of sea ice in that time period. But based on the land surface temperature over Greenland and some high-latitude regions in Russia and Canada we still can figure out that there was a very signifcant warming event before 1950s .

I will add more later today.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 15, 2017, 11:03:25 PM
I have no idea why I cannot post a figure here. I need help!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 15, 2017, 11:11:11 PM
one paper on the circulation change in the Arctic

"Recent summer Arctic atmospheric circulation anomalies in a historical perspective"

A. Belleflamme, X. Fettweis, and M. Erpicum
Laboratory of Climatology, Department of Geography, University of Liège, Allée du 6 Août, 2, 4000 Liège, Belgium
Correspondence to: A. Belleflamme (a.belleflamme@ulg.ac.be)
Received: 18 July 2014 – Published in The Cryosphere Discuss.: 10 September 2014 Revised: 4 December 2014 – Accepted: 7 December 2014 – Published: 7 January 2015


Abstract

 A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500hPa geopotential height data from five reanalysis data sets (ERAInterim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920–1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable.


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 15, 2017, 11:14:08 PM
Quote
#421 on: Today at 11:11:11 PM »

thought this timestamp was pretty cool.

there are two ways to post an image here: 

1.  click the + attachments and other options button below the data entry screen and upload as an attachment (note large files will not be auto sized so >450px will be larger than the viewing window or

2.  click the 'image link' button (second from the left) above the data entry window and add the image url as a link to show in your post.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 15, 2017, 11:25:31 PM
Dr. Ding, if you're reading this, have a look at my question to you in reply 388 above:
http://forum.arctic-sea-ice.net/index.php/topic,1920.msg109633.html#msg109633 (http://forum.arctic-sea-ice.net/index.php/topic,1920.msg109633.html#msg109633)

There I wrote:

I was just reading this:
https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science (https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science)

Quote
Ding said his findings in no way minimize the role of anthropogenic warming in melting sea ice. "I don't want people to take the wrong message in our study, that we're not to blame for Arctic warming," said Ding. "The message is that it's more complex than we expected. In the long term, maybe 100 years from now, the Arctic will become ice free in summer because eventually this internal variability will be overwhelmed by anthropogenic forcing."

Dr. Ding, if you're reading this: were you quoted correctly, and if so, what is your assertion based on, or how should it be interpreted?

As far as I know the Arctic could become ice free at the end of summer much earlier than 100 years from now, and ice free during summer probably (or maybe) also quite a bit earlier than 100 years from now.

So what do you mean by "ice free in summer"? Three months of ice free Arctic from June 21st - Sept 21st? Or is one day without ice in those months also ice free in summer?

And what do you mean by "maybe": would that be your best estimate (so should we read "probably"? Or do you mean " maybe as early as 100 years from now"? And does that imply say a 33% chance, or 25%, or 17% or 10%, or even 5%?

In short, what message exactly do you want to give us, the public?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 15, 2017, 11:27:31 PM
jai mitchell  +1

I've been meaning to say this for a while, and this is offtopic, but your coal/aerosols/sst argument is a courageous one. You are saying that shutting down Coal plants causes short term global warming.  I bet you get a lot of flak for that.

When you first started to state that point, I was suspicious of you because it sounded like a very convenient argument for a climate change denier to take advantage of. But then as you refined the argument and presented more and more evidence I realized that my suspicions of your argument  were nothing but my own personal bias. You are probably right and your argument is very important if coal is going to be phased out.

For example phasing out coal plants during warm cycles of the planet will compound the problems of the warming. Closing them during cool earth cycles will reduce the impact of the short term warming at the cost of maintaining the Earth at a higher temperatures for longer.

This might be an important consideration that is impossible to talk about because of the nature of the debate.

thanks Arch. 

you know the real issue here is that a significant (possibly VERY significant) portion of the cooling impact of upper troposphere SO2 is simply not addressed in the climate models since the physical interactions are not well known. 

With only a modest addition of these impacts and with the recently documented impacts to PDO, AMO and related atmospheric circulation patterns (based on regional emissions/reduction trends in the modern record) much of the supposed variability is washed out INCLUDING the early warming phase in the 1930s that is currently NOT being 100% assigned to anthropogenic activity (just like the intensity of PDO/AMO was also missing significant anthropogenic components).

However some interesting things happen when you work from this assumption that SO2 impacts are severely understated.

1.  The Ruddiman early agriculture hypothesis is proven correct
2.  Arctic sea ice is going to disappear in the next few years (summer minimum)
3.  ECS is closer to 5.5K/2X CO2
4.  we have locked in +3.5C at current atmospheric abundances
5.  We have to start right away with a WWII scale mobilization effort to radically eliminate all fossil fuel consumption in the next 10 years AND begin large scale BEECS/Biochar/Regenerative Agriculture to offset carbon cycle emissions to prevent going over +4C and possibly losing global modernity.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: bbr2314 on April 15, 2017, 11:32:48 PM
jai mitchell  +1

I've been meaning to say this for a while, and this is offtopic, but your coal/aerosols/sst argument is a courageous one. You are saying that shutting down Coal plants causes short term global warming.  I bet you get a lot of flak for that.

When you first started to state that point, I was suspicious of you because it sounded like a very convenient argument for a climate change denier to take advantage of. But then as you refined the argument and presented more and more evidence I realized that my suspicions of your argument  were nothing but my own personal bias. You are probably right and your argument is very important if coal is going to be phased out.

For example phasing out coal plants during warm cycles of the planet will compound the problems of the warming. Closing them during cool earth cycles will reduce the impact of the short term warming at the cost of maintaining the Earth at a higher temperatures for longer.

This might be an important consideration that is impossible to talk about because of the nature of the debate.

thanks Arch. 

you know the real issue here is that a significant (possibly VERY significant) portion of the cooling impact of upper troposphere SO2 is simply not addressed in the climate models since the physical interactions are not well known. 

With only a modest addition of these impacts and with the recently documented impacts to PDO, AMO and related atmospheric circulation patterns (based on regional emissions/reduction trends in the modern record) much of the supposed variability is washed out INCLUDING the early warming phase in the 1930s that is currently NOT being 100% assigned to anthropogenic activity (just like the intensity of PDO/AMO was also missing significant anthropogenic components).

However some interesting things happen when you work from this assumption that SO2 impacts are severely understated.

1.  The Ruddiman early agriculture hypothesis is proven correct
2.  Arctic sea ice is going to disappear in the next few years (summer minimum)
3.  ECS is closer to 5.5K/2X CO2
4.  we have locked in +3.5C at current atmospheric abundances
5.  We have to start right away with a WWII scale mobilization effort to radically eliminate all fossil fuel consumption in the next 10 years AND begin large scale BEECS/Biochar/Regenerative Agriculture to offset carbon cycle emissions to prevent going over +4C and possibly losing global modernity.
I wonder if the global recession beginning in 1929 could be to blame for the spike in Arctic temperatures? Similar to what we are seeing as China winds down its dirtiest pollutants, the "shroud" produced by industry during the roaring 20s would've rapidly been reduced as GDP sputtered by double digits on an annual basis. Of course, wartime efforts beginning in the late 30s revved economies back up in many regions, but I wonder if the 7-8 year period of stagnation and decline could've been a contributing factor to the loss in sea ice, adding a few tenths of a degree to global temps overall before the economy came roaring back to life (along with dirtier industry emitting SO2).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 15, 2017, 11:59:41 PM
If you could understand my thoughts behind our 2017 study, I think it is not hard to understand why I said we probably will see an ice free Arctic summer in 100 years. Actually, I remember that I said "50 to 100 years" to some of the media. Anyway, my point in these interviews is that I believe there is a low frequency mode ( occurs about every 70 years) to partially warm the Arctic in the recent decades and also around 1930-40s and these two warming events may share a similar feature in their dynamics. So when the next one comes after some decades, stronger CO2 forcing and this additional one will cause a much stronger sea ice melting. I only honestly say what I learned from my research. If you don't agree with me, I have no any problem with that.     
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 16, 2017, 12:05:07 AM
Please read this one.
http://neven1.typepad.com/blog/2012/08/similar-melts-from-1938-43.html (http://neven1.typepad.com/blog/2012/08/similar-melts-from-1938-43.html)

I cannot post a picture  from my Pc using that attachment function.



Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 16, 2017, 12:51:45 AM

I wonder if the global recession beginning in 1929 could be to blame for the spike in Arctic temperatures? Similar to what we are seeing as China winds down its dirtiest pollutants.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fgregor.us%2Fwp-content%2Fuploads%2F2016%2F04%2FGlobal-Oil-and-Coal-Consumption-1899-1949-in-Mtoe--e1459792413422.png&hash=4efc2eac93e0d2807f1db5c15b4ac35d)

it should be noted that coal was a common heating fuel during this time and that the reduction of coal use during this time was predominantly in higher temperature processes (rail transport and steel production).  These higher temperature emissions appear to have a much greater impact than lower-temperature combustion products that stay much lower in the atmosphere (and rain out much sooner).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 16, 2017, 01:18:26 AM

I wonder if the global recession beginning in 1929 could be to blame for the spike in Arctic temperatures? Similar to what we are seeing as China winds down its dirtiest pollutants.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fgregor.us%2Fwp-content%2Fuploads%2F2016%2F04%2FGlobal-Oil-and-Coal-Consumption-1899-1949-in-Mtoe--e1459792413422.png&hash=4efc2eac93e0d2807f1db5c15b4ac35d)

it should be noted that coal was a common heating fuel during this time and that the reduction of coal use during this time was predominantly in higher temperature processes (rail transport and steel production).  These higher temperature emissions appear to have a much greater impact than lower-temperature combustion products that stay much lower in the atmosphere (and rain out much sooner).

What are high temperature emissions vs lower temperature combustion prosucts??
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 16, 2017, 02:45:56 AM
in industrial applications coal typically burn at 1350C and some more efficient high-temp pulverized coal power plants operate at 1500-1700C.

open burning of coal in a home fire box typically burns at 600C (at most).

In addition, larger volumes of smokestack emissions allows for greater plume resistance to dispersal and higher altitude atmospheric loading. 

note that the coal smokestacks that we see with white steam coming out are cooled during the scrubbing process to remove (most of) the sulfite.  Non-scrubbed smokestack emissions are clear and very very fast.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 16, 2017, 03:35:53 AM
Wrong thread to discuss, but composition wise they are for all practical purposes similar. Lower temperature combustion emits more CO and hydrocarbons, but other than that it is similar. And since all emissions are in the lower well mixed atmosphere, it does not matter much. CO2 is CO2 no matter the source....
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 16, 2017, 05:20:13 AM
Dr T.

The discussion is about SO2 emissions and their impacts on what we have previously called 'natural variability'.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 16, 2017, 08:22:09 AM
Qinghua Ding,
Thank you for sharing more of your thoughts about natural variability in the Arctic with us.

Regarding your statement
Quote
I believe there is a low frequency mode ( occurs about every 70 years) to partially warm the Arctic in the recent decades and also around 1930-40s and these two warming events may share a similar feature in their dynamics

I don't think there is much evidence in support of this "70 year cycle" hypothesis.

For starters, your reference (from 2006) mentions "Greenland warming of 1920–1930 and 1995–2005", but the end of that last period is now 12 years ago, and the really low sea ice extents happened after that.

More applicable to your paper, if this cycle affects summertime Z200GL then we should see that cycle show up in the summertime NAO index :

(https://climatedataguide.ucar.edu/sites/default/files/styles/node_lightbox_display/public/key_figures/climate_data_set/nao_pc_jja_3.gif?itok=K7FL5cOj)

However, there does not seem to be any specific 70 year cycle there, and there certainly does not seem to be any similarity between the 1930's-40 and the recent decades. If anything the summertime NAO moved positive in the 1930's and moved negative in the last decade.

Regarding Arctic sea ice records dating back to 1850, there is the Walsh reconstruction.
(https://pbs.twimg.com/media/CpfvNsEW8AAbt96.jpg)
Not much of a 70 year (or any) cycle there either.

Regarding the Walsh reconstruction, you may be interested in the work done by Diablo and me in the comment section of this thread :
http://neven1.typepad.com/blog/2016/01/september-arctic-sea-ice-extent-1935-2014.html (http://neven1.typepad.com/blog/2016/01/september-arctic-sea-ice-extent-1935-2014.html)
Specifically, we determined that the Walsh reconstruction contained a few flaws (misplaced Kelly fields and a bias in one of the sources). We then re-computed the Walsh reconstruction with these flaws removed and arrived at a slightly different result, specifically for August :
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi1272.photobucket.com%2Falbums%2Fy396%2FRobDekker%2F1850-2013-Regional_zps47fqu5j5.png&hash=2daf2e94f808f804a4df51703d9d2067)
Still no evidence of any multi-decadal cycle.
Read backward from this post if you are interested in the details :
http://neven1.typepad.com/blog/2016/01/september-arctic-sea-ice-extent-1935-2014.html?cid=6a0133f03a1e37970b01b8d22fd62a970c#comment-6a0133f03a1e37970b01b8d22fd62a970c (http://neven1.typepad.com/blog/2016/01/september-arctic-sea-ice-extent-1935-2014.html?cid=6a0133f03a1e37970b01b8d22fd62a970c#comment-6a0133f03a1e37970b01b8d22fd62a970c)

And for the long term sea ice reconstructions, here is Kinnard et al 2011 :

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F3.bp.blogspot.com%2F-_HFhT0IL-kY%2FTzOQV9XPypI%2FAAAAAAAAB78%2FASWxfwIDA3g%2Fs1600%2F9473558483-650.jpg&hash=46fd8bed3c14b37edf27f0a67a9c5c5d)

One could argue that there is a small decadal (20-40 year) cycle in there, but the amplitude is miniscule compared to the recent decline in sea ice extent. And that plot ends in 2000, with the big drops happening AFTER that.

So I don't see any evidence for any significant "70 year" cycle in either Z200GL, Arctic temperature, nor Arctic sea ice extent.

P.S. To insert an image, you can put the URL in between [img] and [/img ] tags (or use the image icon).
I know there is a way to upload a picture too, but I don't know how to do that.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 16, 2017, 09:15:44 AM
Hi Rob,

Thanks. As I said, sea ice reconstruction data you shown uses a climatology of September sea ice ( for some regions ) for September in 1930s -1940s.
You should be very careful to use that data to understand the long term sea ice change.

the NAO refers to  a dipole mode with a high latitude one and a midlatitude cell. But for sea ice, the most important one is the circulation change over Greenland ( I only used it as the index to do regression , right?). I didn't find a good correlation between sea ice and the other cell over the midlatitudes or the difference between two cells in our 2017 paper. So I didn't use the NAO index to explain sea ice. You misunderstood my idea again. 

 Please read"  Recent summer Arctic atmospheric circulation anomalies in a historical perspective"

A. Belleflamme, X. Fettweis, and M. Erpicum
Laboratory of Climatology, Department of Geography, University of Liège, Allée du 6 Août, 2, 4000 Liège, Belgium
Correspondence to: A. Belleflamme (a.belleflamme@ulg.ac.be)
Received: 18 July 2014 – Published in The Cryosphere Discuss.: 10 September 2014 Revised: 4 December 2014 – Accepted: 7 December 2014 – Published: 7 January 2015


Abstract

 A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500hPa geopotential height data from five reanalysis data sets (ERAInterim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920–1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 16, 2017, 09:19:20 AM
Hi Rob,
for your interests, please read this further. A good review of that earlier event.
http://www.sciencedirect.com/science/article/pii/S1873965211000053 (http://www.sciencedirect.com/science/article/pii/S1873965211000053)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 16, 2017, 09:40:41 AM
Hi Rob,
Please see this plot. The sea ice extent in 1938/sep is even larger than that in 1938/aug. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 16, 2017, 09:41:36 AM
Qinghua,

Hi Rob,

Thanks. As I said, sea ice reconstruction data you shown uses a climatology of September sea ice ( for some regions ) for September in 1930s -1940s.
You should be very careful to use that data to understand the long term sea ice change.

What exactly do you mean when you state that the "sea ice reconstruction data you shown uses a climatology of September sea ice" ?

Are you suggesting that the Walsh reconstruction is flawed ? And if so, in which way ?
Also note that Diablo used a 'climatology' to fill in spatial and temporal gaps, but my method does not. Yet we arrived at very similar results.
And still no notion of a multi-decadal cycle.

Quote
the NAO refers to  a dipole mode with a high latitude one and a midlatitude cell. But for sea ice, the most important one is the circulation change over Greenland ( I only used it as the index to do regression , right?). I didn't find a good correlation between sea ice and the other cell over the midlatitudes or the difference between two cells in our 2017 paper. So I didn't use the NAO index to explain sea ice. You misunderstood my idea again. 

 Please read"  Recent summer Arctic atmospheric circulation anomalies in a historical perspective"

I understand that you did not use NAO index for your paper, but for Z200GL is still a major, direct contributor to NAO. If the 'other' (mid-latitude) cell in NAO does not correlate well with sea ice extent, but the cell over Greenland does, then could it be that the cell over Greenland was affected more by sea ice extent than the mid-latitude cell ?

So a major 'cause' of Z200GL increase (and temperature increase) may be global warming or sea ice extent reduction.

In that line of reasoning, Liu et al 2016 makes sense :
Quote
In recent decades, the Greenland ice sheet has experienced increased surface melt. However, the underlying cause of this increased surface melting and how it relates to cryospheric changes across the Arctic remain unclear. Here it is shown that an important contributing factor is the decreasing Arctic sea ice. Reduced summer sea ice favors stronger and more frequent occurrences of blocking-high pressure events over Greenland. Blocking highs enhance the transport of warm, moist air over Greenland, which increases downwelling infrared radiation, contributes to increased extreme heat events, and accounts for the majority of the observed warming trends. These findings are supported by analyses of observations and reanalysis data, as well as by independent atmospheric model simulations using a state-of-the-art atmospheric model that is forced by varying only the sea ice conditions. Reduced sea ice conditions in the model favor more extensive Greenland surface melting. The authors find a positive feedback between the variability in the extent of summer Arctic sea ice and melt area of the summer Greenland ice sheet, which affects the Greenland ice sheet mass balance. This linkage may improve the projections of changes in the global sea level and thermohaline circulation.
http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0391.1 (http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0391.1)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 16, 2017, 09:45:44 AM
we cited Liu 2016 in our 2017 paper. So we also tested his idea in exp4. We didn't see this response. I can give you some other papers that show that it is hard to get this Z200 pattern if a model is forced by observed sea ice melting in JJA.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 16, 2017, 09:47:47 AM
btw, Liu 2016 only showed the Z500 response not Z200, if I remember it correctly. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 16, 2017, 09:58:30 AM
Thank you Qinghua.
I understand that you dispute Liu et al, and honestly, I have not formed an opinion about that.
But I don't understand why you dispute the Walsh reconstruction.
Quote
Please see this plot. The sea ice extent in 1938/sep is even larger than that in 1938/aug.
Please let me understand this : You claim that in the Walsh reconstruction, September 1938 extent is larger than August 1938 extent. I need to check the numbers on that, but if true, is this a reason for you to claim that there is a 70 year cycle in the record ?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 16, 2017, 10:22:21 AM
If you could understand my thoughts behind our 2017 study, I think it is not hard to understand why I said we probably will see an ice free Arctic summer in 100 years. Actually, I remember that I said "50 to 100 years" to some of the media. Anyway, my point in these interviews is that I believe there is a low frequency mode ( occurs about every 70 years) to partially warm the Arctic in the recent decades and also around 1930-40s and these two warming events may share a similar feature in their dynamics. So when the next one comes after some decades, stronger CO2 forcing and this additional one will cause a much stronger sea ice melting. I only honestly say what I learned from my research. If you don't agree with me, I have no any problem with that.

Qinghua, this suggests that you expect the influence of the 'additional one' to fade soon, warming will lessen, as will the current rate of Arctic sea ice loss. But when I asked (https://forum.arctic-sea-ice.net/index.php/topic,1920.msg108338.html#msg108338) whether "we have any way of knowing when this natural variability might switch again and thus slow down the current rapid rate of Arctic sea ice loss", you answered (https://forum.arctic-sea-ice.net/index.php/topic,1920.msg108342.html#msg108342) "To be honest, I don't know the answer."

Is it possible that the 'additional one' doesn't flip in the next 10-15 years, and that the Arctic goes ice-free in September (below 1 million km2 area/extent)? Because if it is, I don't understand how you can say you expect the Arctic to go ice-free 50 to 100 years from now.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 16, 2017, 10:23:48 AM
Dr. Ding, thank you for your reply.

Yamanouchi 2011, to which you refer, says:
"It is likely that the early 20th century warming in the Arctic was due to a combination of intrinsic internal natural climate variability and positive feedbacks that amplified radiative and atmospheric forcing (Kaufman et al., 2009). Most of the internal climate variability explained by models was of decadal or shorter time scale. However, observed early 20th century warming was inter- or multi-decadal. So, additional factor needs to work, and that should be external forcing and positive feedbacks exist in the Arctic climate system. It is not possible for a single factor to explain the entire warming event. The relative importance and contribution of each warming agent has not yet been resolved. A quantitative estimate of the role of each factor is still to be made not only for the early 20th century warming but also for the recent warming."

Supposing there's a 70-yr natural cycle warming and cooling the Arctic, how would it interact with an AGW-trend? Or put differently: how much sea ice loss would we have seen naturally since 1979 without AGW? And how much could a potential natural cooling trend in de coming decades slow down AGW-driven sea ice loss? Could there be a tipping point, as suggested by some, which makes it hard for the sea ice to recover once a critical part has been lost?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: TerryM on April 16, 2017, 10:39:55 AM

Dr. Qinghua

Would the beginnings of the breakup of Ellesmere's ice shelves over 100 yrs ago, after thousands of years of growth, have any effect on what you consider, "natural variation", and what I might consider to be, "early evidence of AGW"?


Thanks
Terry
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on April 16, 2017, 12:00:05 PM
Dr. Qinghua, seeing as you expect the arctic to go ice-free in 50-100 years based on your research and other knowledge. Should the arctic somehow go ice-free in 5-10 years, will that cause you to revise your estimates of the large role of natural variability?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 16, 2017, 05:09:13 PM
Obviously they've gone over the models dozens of times trying to figure out why they don't match observations.  At some point (Ding et al) someone was bound to come up with the rational idea that maybe it's not being entirely forced, but simply natural variation.

We always hesitate to put anything down to cycles because they're generally the first refuge of deniers like the denizens at WUWT.  But occasionally there *are* cycles that need to be taken into account.  If I recall iceberg records in the north Atlantic do tend to  show a 60 year cycle and this could be part of that natural variation.

As Dr Ding points out, there are numerous lines of evidence that point to a low extent in the 1930s.  This is one of the papers I was thinking of when I wrote the above.

Trends and Variability in Sea Ice and Icebergs off the Canadian East Coast (http://www.tandfonline.com/doi/abs/10.1080/07055900.2015.1057684), Peterson, Pettipas, & A. Rosing Asvid, 2015
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 16, 2017, 09:22:53 PM
Thanks for all your follow-up questions to my yesterday's threads . I will try to answer some of them. 

To Rob,

I didn't make it very clear last night since when I wrote those posts I was responding to some other personal messages/questions from this forum.

As we know, sea ice experiences the minimum state in September. So we should expect to see less sea ice in Sep than that in Aug in all sea ice data. But some old sea ice reconstruction data sets show the opposite way around 1930s because there was no reliable information for Sep sea ice in that time so it has to use a Sep climatology from the later period or the entire period to fill September in that period (1930s-1940s). So we see a bad melting in 1938/aug ( this is from the observations to some extents) but more sea ice in 1938/Sep ( in this month, we actually see a climatology, rather than the reality).

Another thing I am very cautious about when I use these data is that there was no sea ice observation over the Canadian side of the basin in 1930s. So when we compare sea ice in August in that period with Aug sea ice in the present day, I think it is better to only focus on sea ice over the Russian side.

I think Walsh reconstruction is a great resource because it is the almost best data we can use but we still should be cautious about its limitation.

To Oren,

If we would see an ice fee summer in Arctic in 5-10 years. I will say my prediction of 50 to 100 years is wrong.


To TerryM,

Sorry. I am not familiar with that place. I will take a close look at that specific location.

  to Lennart van der Linde

As I said yesterday, I think an internal factor could partially cause the 1930-1940event.
The most intriguing part of that event is that warming exhibited a pretty large scale feature in the Arctic and the area was warmed by something very fast from 1920s to 1930s.  So causes  of this fast warming rate has puzzled me for a long time.

The timing of black-carbon forcing seems to be a little bit earlier.

Co2 could be one factor to cause the fast warming rate of the 1930s event but it should be weaker than its effect in 1990s to 2000s.

What is the key factor?   
 

To Neven,

You asked a very tough but great question. If you agree with my thoughts, I think it is very natural to develop an outlook of the Arctic that we should see a slow down of current melting or a little bit recovery in the near future if the tropical Pacific SST pattern would reverse to a pattern with a warming in the east and a cooling in the west. Actually, this is a pattern we observed from 1960s to 1980s.
 
In our 2014 paper, we argued that the Z200 change over Greenland is due to something originated form the tropics. If we really want to understand and predict the evolution of the very low frequency mode in the tropics, we need good and reliable observations to cover the tropical ocean from the surface to the deep ocean. But we only have good deep ocean observations  ( not only SST) since 2003.

My main message is that we still have some time to save our arctic since some melting was not due to Co2 in the past 20 years. But we should work fast because when the next internal warming period comes, we will see very bad melting. if you ask me how fast, my prediction is 50 to 100 years.


 
 

 


Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 16, 2017, 09:38:37 PM
The most intriguing part of that event is that warming exhibited a pretty large scale feature in the Arctic and the area was warmed by something very fast from 1920s to 1930s.  So causes  of this fast warming rate has puzzled me for a long time.

Reduction in global SO2 emissions

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fforum.arctic-sea-ice.net%2Findex.php%3Faction%3Ddlattach%3Btopic%3D1920.0%3Battach%3D43940%3Bimage&hash=597936dfe3de15bd3c4f85377e1b39e7)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fgregor.us%2Fwp-content%2Fuploads%2F2016%2F04%2FGlobal-Oil-and-Coal-Consumption-1899-1949-in-Mtoe--e1459792413422.png&hash=4efc2eac93e0d2807f1db5c15b4ac35d)


Any current climate scientist who expects the first summer effective ice free date between 2065 and 2115 had better start writing their contribution to the 'mea culpa to humanity and the world' for the AR6 and get ready to start advocating for a WWII mobilization emissions reduction process using non-market forces with total societal mobilization requiring ~1/3 of global GNP per year for 10 years to get to net zero emissions, since his/her obvious over conservatism has directly contributed to the potential collapse of human civilization as a result of mis-communicated risk impacts to policymakers.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 16, 2017, 10:02:19 PM
Qinghua,

Thanks again for your reply. Let me specify my question:

How much sea ice loss would we have seen naturally since 1979 without AGW? Average Sept extent was about 7.35 million km2 from 1979-1988 and about 4.73 million km2 from 2007-2016, according to NSIDC (see fig below).

That's a loss of about 2.62 million km2. If natural variability caused about 40% of this loss, that would be about 1.05 million km2, So about 1.57 million km2 would be due to AGW. Is that a correct interpretation of the conclusion of your recent paper?

And my other question: could there be a tipping point, as suggested by some, which makes it hard for the sea ice to recover once a critical part has been lost? What's your opinion on this?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Darvince on April 17, 2017, 03:32:40 AM
Thanks for all your follow-up questions to my yesterday's threads . I will try to answer some of them. 

Since the IPO and PDO, which are the main tropical variability you discuss, were mainly positive in the early period of 1979-2014, and negative in the later period, and are now once again positive, do you expect the trend in Arctic sea ice minima to be essentially zero over the coming years?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 17, 2017, 03:39:10 AM
I would suggest that Ding et al publish a public apology for their careless research which, frankly, makes no sense to my eyes.

Cant this crap stop?  I suggest you apologize - now.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 17, 2017, 05:58:30 AM
This thread is dead

The top two authors on this paper both believe that the FIRST < 1X10^6 km^2 SIE September minimum will happen around 2065.  Or, this is what they have said publicly.  Whether they ACTUALLY believe this is not clear.

The difference between SIE effectively ice free in 2020-ish vs. 2060-ish is measured in the balance of millions of human lives.

There is no excuse for being this far removed from reality.  Either they are completely incompetent, unaware, overconfident in their supposed knowledge, don't care or are a fifth column element working against the greater good intentionally.

In any case these errors will soon be written in stone as one of the greatest failures in human history.

if there is anyone left to remember.

https://www.youtube.com/watch?v=NmL4t8TclGU (https://www.youtube.com/watch?v=NmL4t8TclGU)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 17, 2017, 06:09:59 AM
There is no excuse for being this far removed from reality.  Either they are completely incompetent, unaware, overconfident in their supposed knowledge, don't care or are a fifth column element working against the greater good intentionally.

Go hang out at WUWT - you make about as much sense.

I'm very sad for this forum.  I never thought it would degenerate to name-calling respected scientists. It's embarassing. 

I guess I'll just join A-Team and Chris Reynolds and stay away.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: bbr2314 on April 17, 2017, 06:16:29 AM
This thread is dead

The top two authors on this paper both believe that the FIRST < 1X10^6 km^2 SIE September minimum will happen around 2065.  Or, this is what they have said publicly.  Whether they ACTUALLY believe this is not clear.

The difference between SIE effectively ice free in 2020-ish vs. 2060-ish is measured in the balance of millions of human lives.

There is no excuse for being this far removed from reality.  Either they are completely incompetent, unaware, overconfident in their supposed knowledge, don't care or are a fifth column element working against the greater good intentionally.

In any case these errors will soon be written in stone as one of the greatest failures in human history.

if there is anyone left to remember.

https://www.youtube.com/watch?v=NmL4t8TclGU (https://www.youtube.com/watch?v=NmL4t8TclGU)
I deleted my earlier comment but I am 100% in agreement with you on this. I think that discussion for discussion's sake does nothing to improve actual discourse if it lacks substance or meaning. I also wonder if any groups backing fossil fuels may be funding the "research" presented in this thread.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: sidd on April 17, 2017, 07:18:14 AM
Prof. Ding there are many on this forum who greatly value your participation and wish you to continue. You have certainly sharpened my thinking on the state of the arctic. If you can, please disregard the personal attacks. If you cannot, I would love to continue this discussion on a mailing list which I would be glad to set up if our host Neven cannot.

sidd
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on April 17, 2017, 07:29:45 AM
Less heat, more light, everyone.  Prof. Ding has engaged us in a lively and productive scientific exchange to both explain the paper and hear our questions and criticism.

If you wish to convince him to abandon his findings, you must present compelling fact and arguments.  This requires patience and careful thought.  if you sought rapid results and gratification, I suggest you discard that expectation.

Your arguments will require:

1) work as thorough and compelling as his own and
2) time for everyone one (including the good professor) to digest it.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 17, 2017, 08:01:11 AM
I don't really mind too much if someone don't like our stuff.

For the tipping point question, I think this paper is pretty informative.

Have a great week!

http://eisenman.ucsd.edu/papers/Armour-Eisenman-Blanchard-McCusker-Bitz-2011.pdf (http://eisenman.ucsd.edu/papers/Armour-Eisenman-Blanchard-McCusker-Bitz-2011.pdf)

The reversibility of sea ice loss in a state‐of‐the‐art climate model K. C. Armour,1 I. Eisenman,2,3 E. Blanchard‐Wrigglesworth,3 K. E. McCusker,3 and C. M. Bitz3 Received 29 June 2011; accepted 15 July 2011; published 20 August 2011.

 [1] Rapid Arctic sea ice retreat has fueled speculation about the possibility of threshold (or ‘tipping point’) behavior and irreversible loss of the sea ice cover. We test sea ice reversibility within a state‐of‐the‐art atmosphere– ocean global climate model by increasing atmospheric carbon dioxide until the Arctic Ocean becomes ice‐free throughout the year and subsequently decreasing it until the initial ice cover returns. Evidence for irreversibility in the form of hysteresis outside the envelope of natural variability is explored for the loss of summer and winter ice in both hemispheres. We find no evidence of irreversibility or multiple ice‐cover states over the full range of simulated sea ice conditions between the modern climate and that with an annually ice‐free Arctic Ocean. Summer sea ice area recovers as hemispheric temperature cools along a trajectory that is indistinguishable from the trajectory of summer sea ice loss, while the recovery of winter ice area appears to be slowed due to the long response times of the ocean near the modern winter ice edge. The results are discussed in the context of previous studies that assess the plausibility of sea ice tipping points by other methods. The findings serve as evidence against the existence of threshold behavior in the summer or winter ice cover in either hemisphere. Citation: Armour, K. C., I. Eisenman, E. Blanchard‐Wrigglesworth, K. E. McCusker, and C. M. Bitz (2011), The reversibility of sea ice loss in a stateof‐the‐art climate model, Geophys. Res. Lett., 38, L16705, doi:10.1029/2011GL048739.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Qinghua ding on April 17, 2017, 08:05:56 AM
To Darvince
I don't know the answer. I don't think our models have a good skill to predict either the PDO or IPO.   
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 17, 2017, 10:52:12 AM
As I've written in another thread (https://forum.arctic-sea-ice.net/index.php/topic,1957.0.html) that sidd has opened with regards to setting up a private mailing list:

Quote
Ever since Qinghua Ding engaged here, the 'abuse' has become even less. On the other hand he does say (based on his research) that the Arctic won't go ice-free for another 50-100 years, so some push-back is to be expected on a forum for people who are worried about AGW.

Okay, so I wrote this before reading the last couple of comments.  ;)

I'm also not sure if there is a lot of value for society (now and in the future) to state that there is some 70-year cycle that will cause the Arctic to go ice-free many decades later than most experts currently think, especially if there is no way of projecting or monitoring the cycle, let alone determining how AGW has influenced this cycle itself. What if this gets a lot of traction, but it turns out to be wrong? At face value, it gives a false sense of security (also caused by the misleading character of the word 'ice-free', which implies that the consequences won't kick into action before then).

But scientifically it's interesting, and we'll have to wait and see whether more groups will continue to build on this research.

Either way, I want to thank Qinghua again for engaging here, being a good sport and realizing that this is the Internet where it's easier to vent frustrations, etc. I would kindly like to ask everyone to refrain from posting, unless there is something new to be said/asked about the science. There is no use in going through the same motions again, and ending with disparaging remarks.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 17, 2017, 01:55:20 PM
Qinghua,

Thank you for referring to Armour et al 2011.

They say:
“Although we find that CCSM3 does not show evidence of a summer sea ice tipping point, the variance in summer Arctic sea ice area increases in the model as the climate warms [Holland et al., 2008; Goosse et al., 2009]. The increase in variance may plausibly be related to a reduction in stability, or alternatively it may be driven by other factors such as reduced geographic muting of ice edge variability [Goosse et al., 2009; Eisenman, 2010] or an overall thinning of the ice pack [Notz, 2009]. However, in light of the present findings, it does not appear to be associated with a loss of stability altogether. Given that these same processes are expected to be at work in nature, variance in the observed sea ice cover may similarly be an unreliable indicator of an approaching threshold.”

Livina & Lenton 2013 say on potential Arctic sea ice tipping points:
http://www.the-cryosphere.net/7/275/2013/tc-7-275-2013.pdf (http://www.the-cryosphere.net/7/275/2013/tc-7-275-2013.pdf)

"there has been an abrupt and persistent jump in the amplitude of the seasonal cycle of Arctic sea-ice cover in 2007 (Ditlevsen, 2012), but the underlying causal mechanism remains uncertain. We describe this as a (non-bifurcation) “tipping point”, because it involved an abrupt, qualitative change in the sea-ice dynamics, without any evidence for a large forcing perturbation; i.e. the abruptness resides in the internal dynamics of the Arctic climate system."

And Serreze 2011 says:
http://www.nature.com.sci-hub.cc/nature/journal/v471/n7336/full/471047a.html (http://www.nature.com.sci-hub.cc/nature/journal/v471/n7336/full/471047a.html)

"with ice-free summers, the ocean picks up a great deal of extra heat, delaying autumn ice growth. If there was a tipping point, this summer heat gain would lead to ice cover the following spring being thin enough to completely melt out over the following summer. Instead, so much ocean heat is lost during the darkness of the polar winter that enough ice grows to survive the next summer’s melt."

The question seems to be: will it? Or will Arctic amplification feedbacks cause much of this extra heat uptake to stay in the Arctic? If so, how large will this amplification be? Even if there is no irreversibility, there still could maybe be an acceleration in ice loss. It seems a risk we can't ignore yet.

Also if we look again at fig 8 of Walsh et al 2016 (attached):
http://onlinelibrary.wiley.com/doi/10.1111/j.1931-0846.2016.12195.x/full (http://onlinelibrary.wiley.com/doi/10.1111/j.1931-0846.2016.12195.x/full)

It shows maybe 0.5 million km2 decadal variability from 1850-1925 and about 1 million km2 from 1925-2000. Why has this decadal variability apparently grown? Could it be due to AGW? In that case maybe part of the 1.05 million km2 loss from 1979-1988 to 2007-2016 is not fully due to natural variability, but also partly to AGW, say 50% of it? In that case natural variability would have caused about 20% of ice loss since 1979 instead of 40%. Or how would this argument be mistaken?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 18, 2017, 04:06:43 AM
Hi Rob,
Please see this plot. The sea ice extent in 1938/sep is even larger than that in 1938/aug.

I cannot reproduce that.
https://nsidc.org/data/g10010

From the Walsh data, I obtain for ice 'extent' :

1938 8 : 8.45
1938 9 : 7.95

That's a 500 k km^2 drop between August and September, which is typical.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 18, 2017, 04:25:28 AM
Qinghua Ding said
Quote
I also checked all these old sea ice reconstruction data from month to month before 1950s. I think they used a climatology of September from some periods later for all September sea ice before 1950s or 60s. As I know, old sea ice data/charts only recorded sea ice information from April to Aug.  I can plot some old ice data later. you will see what I mean here.

Actually, Walsh et al did not use a 'climatology'.
They used a spacial/temporal 'analog' method, using regional matches to obtain ice concentration in locations where there were no observations.

Also, September is a very hard month to reconstruct, since especially before 1953 there are very few ice (edge) observations in September.

August has more observations, and thus is easier to reconstruct for the earlier record :

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi1272.photobucket.com%2Falbums%2Fy396%2FRobDekker%2F1850-2013-Regional_zps47fqu5j5.png&hash=2daf2e94f808f804a4df51703d9d2067)

Here you see the reconstruction from Walsh et al for August, and the reconstruction that I compiled with Diablo (from this thread) :
http://neven1.typepad.com/blog/2016/01/september-arctic-sea-ice-extent-1935-2014 (http://neven1.typepad.com/blog/2016/01/september-arctic-sea-ice-extent-1935-2014)

Both Walsh and my methods are 'analog' based and Diablo's own method is 'climatology' based, but all 3 reconstructions show a 'dip' in the 30's and 40's, which is likely caused by the higher Arctic temperatures prevalent at the time, which appears to be pan-Arctic.

Yet it should be clear that the magnitude of the 'dip' around the 30's and 40's is minor compared to the decline in Arctic sea ice that we observe from the satellite era (80's to present).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Lennart van der Linde on April 18, 2017, 08:51:45 AM
Yet it should be clear that the magnitude of the 'dip' around the 30's and 40's is minor compared to the decline in Arctic sea ice that we observe from the satellite era (80's to present).

Yes, and the question seems to be: how big was this dip in the 30s-40s, and what part of it was natural variability and what part antropogenic (including possibly aerosols)?

Walsh et al say:
"Figure 8 provides further temporal context by showing the March and September ice extents for every year in the database. The time series for both months contain considerable interannual variability (variances of approximately a million km2 about a 10-year running mean), in contrast to earlier depictions such as HadISST1 (Rayner et al. 2003) that contained climatological fields in earlier decades. Except for the recent (post-1970) decrease of ice cover in both seasons, there is little indication of decadal or multidecadal variability in the pan-Arctic ice extent. However, there are indications of a decrease in September extent from the 1920s to the 1940s, followed by an increase to a relative maximum by the 1970s."

Looking at their Sept extent interannual variability seems closer to 0.5 million km2 for the first half of the time-period (1850-1930), and much larger for the second half (1930-2010). Is that due to a combination of say a 70-yr natural cycle and AGW, and if so, what combination?

My guestimate based on the discussion so far would be about 20% natural at the most, if at all (aerosols?), and at least 80% AGW, but if others have better estimates, let us hear them. Part of the decrease that Ding et al ascribe to natural variability should possibly/probably be ascribed to AGW, it seems to me. And potentially aerosols have prevented even faster extent decreases. I think Ding et al have not responded convincingly to these arguments yet, or if they have, I've missed it.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 18, 2017, 09:49:47 PM

In my opinion this is overconfidence in models, on global scale i would agree but in arctic i would be carefully (...)

This was very fast, that my opinion about using Model Mean becomes a Paper: http://onlinelibrary.wiley.com/doi/10.1002/2016GL072342/abstract?utm_content=buffer4dd3e&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer (http://onlinelibrary.wiley.com/doi/10.1002/2016GL072342/abstract?utm_content=buffer4dd3e&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer)

"The multi-model ensemble mean is hence not representative of a consensus across the models in Arctic climate projections."

This is why i told before, that mean of models must not represent the forced response
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 19, 2017, 04:34:38 AM
Lennart
Quote
Yes, and the question seems to be: how big was this dip in the 30s-40s, and what part of it was natural variability and what part antropogenic (including possibly aerosols)?

From the reconstructions of pre-satellite Arctic sea ice, we know that the 30s-40s dip was there, but here is a lot of annual 'noise' in the August data, which makes it hard to say exactly how much decline there was. The 20% (of satellite era decline) that you mention looks reasonable.

As for the cause of the 30s-40s dip, I think the prime suspect is the AMO.
We know that high latitude Northern Atlantic SST's went up fast in the 20's and peaked in the 30's and 40's :

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fimages.huffingtonpost.com%2F2015-02-12-Sci15FigHuffPost.png&hash=8d248855ae85597a23cca1775c2af37b)

Note this is the REAL AMO, not the AMO index, which is tainted by anthropogenic signals (warming and aerosol cooling). More about that from Michael Mann himself here :
http://www.realclimate.org/index.php/archives/2015/02/climate-oscillations-and-the-global-warming-faux-pause/ (http://www.realclimate.org/index.php/archives/2015/02/climate-oscillations-and-the-global-warming-faux-pause/)
and in the scientific paper about 'teasing' out the REAL AMO from the climate data :
http://onlinelibrary.wiley.com/doi/10.1002/2014GL059233/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2014GL059233/abstract)

All this suggests that, yes, there is decadal natural variability in the (Arctic) climate, but it is limited in amplitude, and we need to be very careful when attributing any change in the climate to anthropogenic or natural causes.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 19, 2017, 05:39:44 AM
There is no excuse for being this far removed from reality.  Either they are completely incompetent, unaware, overconfident in their supposed knowledge, don't care or are a fifth column element working against the greater good intentionally.

Go hang out at WUWT - you make about as much sense.

I'm very sad for this forum.  I never thought it would degenerate to name-calling respected scientists. It's embarassing. 

I guess I'll just join A-Team and Chris Reynolds and stay away.

(Off-topic, sorry)

I have checked Chris Reynolds' last posts here on ASIF and on his blog. Apparently he is just too busy with personal matters to continue posting about Arctic sea ice. So if he is "staying away", it's for personal reasons, and not because of anything anybody posted here on ASIF.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 19, 2017, 07:24:56 AM
There is also a PDO and AMOC pattern that follows the AMO and -NAO.

I know of only one variable that could possibly produce impacts to all of these. 


Aerosols

1st image AMO and NAO
2nd image AMOC
3rd image PDO

the All metrics show a systemic change beginning in the early 1920s.   

These graphs clearly show (to me) that the GHG forcing driver was present, significant and starting the shift toward +PDO, Stronger Trades (AMO) and positive NAO. 
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 19, 2017, 07:43:19 AM
indeed it does appear that the collapse in Coal consumption began pre-1920.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Andreas T on April 19, 2017, 10:04:01 AM
since this graph shows percentages, you would need to show how the total is changing (increasing) for this to illustrate how much coal burning has taken place. You also don't make clear what the graph represents. From the large decrease in oil consumption in WW2 I deduce that it shows a limited region of the world, Europe? Italy?
What can you tell from it?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: RoxTheGeologist on April 19, 2017, 05:51:27 PM

US consumption increased continually until 2008.

https://www.eia.gov/coal/review/coal_consumption.php (https://www.eia.gov/coal/review/coal_consumption.php)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 19, 2017, 06:11:17 PM
the spike in global wood fuel in the post world war I recession and 1920 depression indicates that, from an energy use perspective, its effects was much greater than the great depression from an aerosols perspective.  The sudden change of aerosol emissions driven by economic cycles is the only variable that has the potential to impact the global circulation patterns on such a short time scale.  I made a hypothesis that the shifts happened before the great depression (in the 1920's) and I was able to find out that indeed, the aerosol emission shift actually happened during that time - as opposed to what I had believed previously.

Also that the shift in PDO to positive indicated that there was significant forcing pent up in the system, which causes a sudden shift in atmospheric and ocean circulations when the cork is released by suddenly cutting aerosol emissions.  In a Dynamic Fluid system when this happens there is always an impact that swings far beyond equilibrium.  Hence a definitive signal can be derived from the period.  AND since recent studies all indicate aerosol impacts to these circulation metrics (AMO, AMOC, PDO, NAO) it can be reasonably deduced that a significant part of what was considered 'natural variability' at the time was actually driven by regional SO2 emissions reductions and GHG forcing -- contrary to the current assumption that we cannot determine the cause of early period warming by the IPCC.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 19, 2017, 06:28:45 PM
I wonder if the proliferation of underground nuclear weapons testing after ww2 produced enough aerosols to make a difference in global temperatures.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 19, 2017, 06:43:11 PM
do you mean above ground nuclear testing? the purpose of below ground is to prevent atmospheric impacts.  I would have to look at it but my sense is that the amount is insignificant compared to global coal emissions at that time.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 19, 2017, 06:46:49 PM
do you mean above ground nuclear testing? the purpose of below ground is to prevent atmospheric impacts.  I would have to look at it but my sense is that the amount is insignificant compared to global coal emissions at that time.

My thinking is that if  many nuclear weapons cause nuclear winter, a few may slow down global warming. I get the feeling that nuclear weapons had at least at small part in the cooling after 1945.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Andreas T on April 19, 2017, 07:07:22 PM
the spike in global wood fuel in the post world war I recession and 1920 depression indicates that, from an energy use perspective, its effects was much greater than the great depression from an aerosols perspective.  The sudden change of aerosol emissions driven by economic cycles is the only variable that has the potential to impact the global circulation patterns on such a short time scale.  I made a hypothesis that the shifts happened before the great depression (in the 1920's) and I was able to find out that indeed, the aerosol emission shift actually happened during that time - as opposed to what I had believed previously.
......
global wood fuel use (or coal use) is not shown in the graph you posted, do you have another source?
the graph seems to come from a paper which states in its abstract:
Quote
This article examines energy consumption in Sweden, Holland, Italy and Spain over 200 years, including both traditional and modern energy carriers.
and is labelled "The Italian energy transition, 1861-2000"
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 19, 2017, 07:08:38 PM
do you mean above ground nuclear testing? the purpose of below ground is to prevent atmospheric impacts.  I would have to look at it but my sense is that the amount is insignificant compared to global coal emissions at that time.

My thinking is that if  many nuclear weapons cause nuclear winter, a few may slow down global warming. I get the feeling that nuclear weapons had at least at small part in the cooling after 1945.

Depends how high will the dust cloud go. Some volcanoes are more efficient in doing so. What percentage of nuclear tests were surface vs underground?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 19, 2017, 07:19:02 PM
it is still a good indication,

U.S. and UK consumption patters also follow the similar trend shown here:  https://ourworldindata.org/energy-production-and-changing-energy-sources/ (https://ourworldindata.org/energy-production-and-changing-energy-sources/)

In addition, the real powerhouse of the time was Germany who in post WWI the Versailles Treaty had a massive hyperinflation and collapsed economy.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fnet.lib.byu.edu%2F%7Erdh7%2Fwwi%2F1918p%2Frep27%2Fimages%2Fgraph12.gif&hash=5ccdd78aa9c3c4da64a4cdefc8084e26)

(https://fred.stlouisfed.org/graph/fredgraph.png?id=M0119CDEM422NNBR&nsh=1)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 19, 2017, 07:21:17 PM
From wikipedia:

Quote
As of 1993, worldwide, 520 atmospheric nuclear explosions (including 8 underwater) have been conducted with a total yield of 545 megaton (Mt): 217 Mt from fission and 328 Mt from fusion, while the estimated number of underground nuclear tests conducted in the period from 1957 to 1992 is 1,352 explosions with a total yield of 90 Mt.[4]

https://en.wikipedia.org/wiki/List_of_nuclear_weapons_tests

Then on the Nuclear weapons testing page they say this about atmospheric weapons testing (my emphasis)

Quote
Atmospheric testing designates explosions that take place in the atmosphere. Generally these have occurred as devices detonated on towers, balloons, barges, islands, or dropped from airplanes, and also those only buried far enough to intentionally create a surface-breaking crater. Nuclear explosions close enough to the ground to draw dirt and debris into their mushroom cloud can generate large amounts of nuclear fallout due to irradiation of the debris. This definition of atmospheric is used in the Limited Test Ban Treaty, which banned this class of testing along with exoatmospheric and underwater.

https://en.wikipedia.org/wiki/Nuclear_weapons_testing

I imagine the bolded type of testing had the potential for the most cooling because it ejects the most particles.

How does a nuclear weapons test compares to large volcano eruptions? If they are similar on matter ejected and height of ejection then Nuclear weapons might have played a significant role.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 19, 2017, 07:32:47 PM
From wikipedia:

Quote
As of 1993, worldwide, 520 atmospheric nuclear explosions (including 8 underwater) have been conducted with a total yield of 545 megaton (Mt): 217 Mt from fission and 328 Mt from fusion, while the estimated number of underground nuclear tests conducted in the period from 1957 to 1992 is 1,352 explosions with a total yield of 90 Mt.[4]

https://en.wikipedia.org/wiki/List_of_nuclear_weapons_tests

Then on the Nuclear weapons testing page they say this about atmospheric weapons testing (my emphasis)

Quote
Atmospheric testing designates explosions that take place in the atmosphere. Generally these have occurred as devices detonated on towers, balloons, barges, islands, or dropped from airplanes, and also those only buried far enough to intentionally create a surface-breaking crater. Nuclear explosions close enough to the ground to draw dirt and debris into their mushroom cloud can generate large amounts of nuclear fallout due to irradiation of the debris. This definition of atmospheric is used in the Limited Test Ban Treaty, which banned this class of testing along with exoatmospheric and underwater.

https://en.wikipedia.org/wiki/Nuclear_weapons_testing

I imagine the bolded type of testing had the potential for the most cooling because it ejects the most particles.

How does a nuclear weapons test compares to large volcano eruptions? If they are similar on matter ejected and height of ejection then Nuclear weapons might have played a significant role.

I think they were a blip re cooling
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 19, 2017, 07:41:38 PM
From Sceptical Science: http://www.skepticalscience.com/nuclear.html (http://www.skepticalscience.com/nuclear.html)

The majority of large yield tests were in the early sixties..most of cooling in a war would be from the resulting fires and their smoke and ash. Not from the nuclear explosion themselves...
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 19, 2017, 07:52:52 PM
https://www.wunderground.com/resources/climate/nuke.asp (https://www.wunderground.com/resources/climate/nuke.asp)

Quote
Their most recent paper, a December 2008 study titled, "Environmental Consequences of Nuclear War", concludes that "1980s predictions of nuclear winter effects were, if anything, underestimates". Furthermore, they assert that even a limited nuclear war poses a significant threat to Earth's climate. The scientists used a sophisticated atmospheric/oceanic climate model that had a good track record simulating the cooling effects of past major volcanic eruptions, such as the Philippines' Mt. Pinatubo in 1991. The scientists injected five terragrams (Tg) of soot particles into the model atmosphere over Pakistan in May of 2006. This amount of smoke, they argued, would be the likely result of the cities burned up by a limited nuclear war involving 100 Hiroshima-sized bombs in the region. India and Pakistan are thought to have 109 to 172 nuclear weapons of unknown yield.

The intense heat generated by the burning cities in the models' simulations lofted black smoke high into the stratosphere, where there is no rain to rain out the particles. The black smoke absorbed far more solar radiation than the brighter sulfuric acid aerosol particles emitted by volcanic eruptions. This caused the smoke to heat the surrounding stratospheric air by 30°C, resulting in stronger upward motion of the smoke particles higher into the stratosphere. As a result, the smoke stayed at significant levels for over a decade (by contrast, highly reflective volcanic aerosol particles do not absorb solar radiation and create such circulations, and only stay in the stratosphere 1-2 years). The black soot blocked sunlight, resulting in global cooling of over 1.2°C (2.2°F) at the surface for two years, and 0.5°C (0.9°F) for more than a decade (Figures 1 and 2). Precipitation fell up to 9% globally, and was reduced by 40% in the Asian monsoon regions. 


The scenario is different because it is talking about 100 nuclear weapon over a very small time and local frame . Nuclear testing were staggered over a few decades, but maybe each testing was a blip, and the accumulation of blips, had a measurable impact on global temps.
 

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 19, 2017, 08:18:23 PM
Might be getting OT :)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Blizzard92 on April 19, 2017, 08:27:27 PM
On the discrepancy between observed and CMIP5 multi-model simulated Barents Sea winter sea ice decline [Li et al., 2017]

https://www.nature.com/articles/ncomms14991 (https://www.nature.com/articles/ncomms14991)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Random_Weather on April 19, 2017, 08:32:10 PM
@ Blizz

Look also here: http://forum.arctic-sea-ice.net/index.php/topic,1920.msg110212.html#msg110212 (http://forum.arctic-sea-ice.net/index.php/topic,1920.msg110212.html#msg110212)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: magnamentis on April 19, 2017, 08:53:47 PM
There is no excuse for being this far removed from reality.  Either they are completely incompetent, unaware, overconfident in their supposed knowledge, don't care or are a fifth column element working against the greater good intentionally.

Go hang out at WUWT - you make about as much sense.

I'm very sad for this forum.  I never thought it would degenerate to name-calling respected scientists. It's embarassing. 

I guess I'll just join A-Team and Chris Reynolds and stay away.

IMHO to give those who strongly disagree and IMO are even right the feeling that they destroy a forum is at least as bad as throwing in thoughts about unbelievable things for consideration.

and then to press on the tear glands is typical female behavior, first yell then cry.

however anything that is far from "how it currently looks like" may well be questioned no matter who stands behind the theory, which is how mankind came that far ( far not only equals good but still )

scientist themselves work after the "negative principle" lives from permanent doubts and questioning that hopefully will end up with proof one day before it's too late.

however to take a clear stance, i would bet almost anything that we shall be more or less ice free in summer way before 2060-ies, can't proof but is my personal opinion and a valid one as per my best knowledge. can't see why opposing people with a "name" should not be allowed or do you prefer your surgeon to use a hammer to knock you out for operation LOL. beside the fact that we all make mistakes and at times loose temper or oversight this should never be a lasting and general habit. those who could not deal with things that way are the ones you mentioned, hence no problem here if you join them and rant over there [pun intended]
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 19, 2017, 09:11:27 PM
Might be getting OT :)

Yeah. To try bring it back on topic and tie it with coal emissions, 1930's warming and the natural or anthropogenic nature of the loses in sea ice, humans are a force of nature. Our impact on the planet is very significant. We are probably the main driver of variability of the climate system. Human impact on the climate system was insignificant more than 10k years ago. Our impact was similar to any other invasive species. It was slight but significant during the past 10k years. Mass agriculture and deforestation started to become global. About 200 years ago, with the dawn of the industrial revolution, our impact on the planet increased  to the point that we are the primary drivers of the variability of the climate system.

Attributing any cycle to "natural variation" requires very clear evidence of the forcings causing the variation. Random variation, internal variation, unknown variations, noise, sure that exists but is almost impossible that they have not been affected by human interference.

We are driving the climate, except we are driving blind.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Williams on April 19, 2017, 09:21:22 PM
We are driving the climate, except we are driving blind.

To put it another way.  We are the Unknown Unknowns.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Andreas T on April 19, 2017, 10:13:32 PM
it is still a good indication,

U.S. and UK consumption patters also follow the similar trend shown here:  https://ourworldindata.org/energy-production-and-changing-energy-sources/ (https://ourworldindata.org/energy-production-and-changing-energy-sources/)

In addition, the real powerhouse of the time was Germany who in post WWI the Versailles Treaty had a massive hyperinflation and collapsed economy.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fnet.lib.byu.edu%2F%7Erdh7%2Fwwi%2F1918p%2Frep27%2Fimages%2Fgraph12.gif&hash=5ccdd78aa9c3c4da64a4cdefc8084e26)

(https://fred.stlouisfed.org/graph/fredgraph.png?id=M0119CDEM422NNBR&nsh=1)
At the risk of stretching this into OT territory, but since we are talking about the quality of evidence as well, I'll make another comment.
The short but very deep drop in Germany's coal production is most likely the effect of the 1923 occupation of the Ruhr, its main coal producing area. Again not representative of global consumption.
But you seem to be saying that to match the pattern of global temperatures, there needs to be an early 1920s dip in albedo increasing aerosols if I understand correctly?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: bbr2314 on April 19, 2017, 10:38:32 PM
the spike in global wood fuel in the post world war I recession and 1920 depression indicates that, from an energy use perspective, its effects was much greater than the great depression from an aerosols perspective.  The sudden change of aerosol emissions driven by economic cycles is the only variable that has the potential to impact the global circulation patterns on such a short time scale.  I made a hypothesis that the shifts happened before the great depression (in the 1920's) and I was able to find out that indeed, the aerosol emission shift actually happened during that time - as opposed to what I had believed previously.

Also that the shift in PDO to positive indicated that there was significant forcing pent up in the system, which causes a sudden shift in atmospheric and ocean circulations when the cork is released by suddenly cutting aerosol emissions.  In a Dynamic Fluid system when this happens there is always an impact that swings far beyond equilibrium.  Hence a definitive signal can be derived from the period.  AND since recent studies all indicate aerosol impacts to these circulation metrics (AMO, AMOC, PDO, NAO) it can be reasonably deduced that a significant part of what was considered 'natural variability' at the time was actually driven by regional SO2 emissions reductions and GHG forcing -- contrary to the current assumption that we cannot determine the cause of early period warming by the IPCC.
the more we delve into this the more sense it makes (IMO) and I *highly hugely wish* that we had actual funding to explore this area of research further.

re: nuclear weapons testing, i would think that if there was any primary effect it would've been on ozone? besides that, the weapons being tested were being detonated in regions remote/barren enough to avoid substantial fallout in the vast majority of cases. i'm sure a Siberian forest or two went up in smoke thanks to the Russians, but beyond that, the "nuclear winter" aspect following any war is due to the cities/etc burning and being thrown into the atmosphere. with testing, this was not a goal or an outcome.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 19, 2017, 10:44:53 PM

and then to press on the tear glands is typical female behavior, first yell then cry.


Stupid and sexist - what a freaking combo.   You're lower than the typical WUWT commenter.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 19, 2017, 10:56:26 PM

But you seem to be saying that to match the pattern of global temperatures, there needs to be an early 1920s dip in albedo increasing aerosols if I understand correctly?

No, I am saying that the global circulation impacts pointed to a significant reduction at this time, I looked at the available data and it shows a post WWI recession that was global in nature and, including a massive drop in the most productive economy at that time (Germany) showed that I was reading the PDO, AMO, AMOC and NAO transition correctly.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 19, 2017, 11:09:03 PM
In the simulation they run 100 nuclear detonations and obtain the first image attached. If 100 nuclear weapons can lower the global temperature 1.2C for almost a decade then a naive calculation results that 1 nuclear weapon would lower the temps for .012 for probably much less time.

There where 520 atmospheric nuclear weapons test in the time period in question. Lets say that only 10% of those were in simulated cities, forests or other environments were enough particulates were present. Then that's 52 tests at .012 degrees each that's .624 degrees. Of course they didn't happen at the same time but that very back of the envelope calculation gives a good idea of the total forcing.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 20, 2017, 01:00:36 AM
In the simulation they run 100 nuclear detonations and obtain the first image attached. If 100 nuclear weapons can lower the global temperature 1.2C for almost a decade then a naive calculation results that 1 nuclear weapon would lower the temps for .012 for probably much less time.

There where 520 atmospheric nuclear weapons test in the time period in question. Lets say that only 10% of those were in simulated cities, forests or other environments were enough particulates were present. Then that's 52 tests at .012 degrees each that's .624 degrees. Of course they didn't happen at the same time but that very back of the envelope calculation gives a good idea of the total forcing.

Getting to be OT.  However their sims assumed lots of fires due to nuclear weapons. No significan fires from testing.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: AndrewB on April 20, 2017, 02:37:01 AM
I wonder if the proliferation of underground nuclear weapons testing after ww2 produced enough aerosols to make a difference in global temperatures.
(Off-topic, sorry)
Underground nuclear weapons tests produced essentially zero airborne particles. Above ground nuclear weapons tests produced a specific kind of airborne particles that didn't stay long enough in the atmosphere (too heavy, falling quickly enough to the ground) and didn't reach high enough layers to cause any measurable global dimming effect.
Nuclear winter is a theory (untested, thankfully, and let's hope it remains so) that if enough thermonuclear (hydrogen) bombs are exploded over cities, the resulting fires would raise an enormous amount of ashes and these particles would then result in enough NH dimming for some 5~10 years to kill most trees and plants, hence starving whatever population would be left.

Takeaway from all this: past nuclear weapons tests are irrelevant to any serious discussion about climate change, past or present.

https://en.wikipedia.org/wiki/List_of_nuclear_weapons_tests
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on April 20, 2017, 02:46:12 AM
Quick off the cuff thought - I'm piqued by the idea the 30s/early 40s temperature bump could be a result of decreased aerosols (SO2 in particular) tied to the reduction in industrial zctivity and fossil fuel consumption during the depression.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: DrTskoul on April 20, 2017, 02:51:58 AM
Quick off the cuff thought - I'm piqued by the idea the 30s/early 40s temperature bump could be a result of decreased aerosols (SO2 in particular) tied to the reduction in industrial zctivity and fossil fuel consumption during the depression.

Too small of contribution. If climate is that sensitive we are 100% irrevocably screwed....
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on April 20, 2017, 03:40:20 AM
Ok then. I'll assume most nuclear weapons test were not done on the surface near forests or cities so no firestorm formed, except at Hiroshima. There a firestorm formed. It's effect on global temperatures is unknown but probably small. Just one more negative force. Curiosity satisfied. Thanks.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 20, 2017, 05:05:23 AM
Quick off the cuff thought - I'm piqued by the idea the 30s/early 40s temperature bump could be a result of decreased aerosols (SO2 in particular) tied to the reduction in industrial zctivity and fossil fuel consumption during the depression.

I doubt that the 30s-40s temperature bump had much to do with aerosols.
The AMO is a much more likely candidate.
After all, Delworth and Mann 2000 extracted (approx. 70 year) AMO cycles back 400 years from climate proxy data, including this one from the 30s-40s :

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi1272.photobucket.com%2Falbums%2Fy396%2FRobDekker%2FScreen%2520Shot%25202017-04-19%2520at%25207.47.45%2520PM_zpse3vglife.png&hash=3f49179456f6488a90080b0427f318a7)
[edit: if for some reason that picture does not come through, then please check Figure 3a in the paper]

Full paper here :
http://www.meteo.psu.edu/holocene/public_html/shared/articles/delworthmann.pdf (http://www.meteo.psu.edu/holocene/public_html/shared/articles/delworthmann.pdf)

Also Kinnard et al 20011 shows a small amplitude multi-decadal cycle pattern in their Arctic sea ice reconstructions :

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F3.bp.blogspot.com%2F-_HFhT0IL-kY%2FTzOQV9XPypI%2FAAAAAAAAB78%2FASWxfwIDA3g%2Fs1600%2F9473558483-650.jpg&hash=46fd8bed3c14b37edf27f0a67a9c5c5d)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 06:13:47 AM

I doubt that the 30s-40s temperature bump had much to do with aerosols.
The AMO is a much more likely candidate.


http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.652.3232&rep=rep1&type=pdf (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.652.3232&rep=rep1&type=pdf)

Quote
Here we use a state-  of-the-art earth system climate model, to show that aerosol emissions and periods of volcanic activity explains 76% of the simulated multidecadal variance in
detrended 1860 to 2005 North Atlantic SST. After 1950 simulated variability is
within observational estimates; from 1910-1940 our estimates capture twice the
warming of previous generation models, but do not explain the entire observed
trend. Other processes, such as ocean circulation, may also have contributed to
early 20th century variability. Mechanistically, we find that inclusion of aerosol cloud
microphysical effects, rarely included within previous multi-models
ensembles, dominates the magnitude (80%) and spatial pattern of the total
surface aerosol forcing in the North Atlantic.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 06:18:19 AM
https://pdfs.semanticscholar.org/821e/f923d31e8eb3db38ce6c961d23cf4e297815.pdf

Quote
In summary, our results are supportive of the hypothesis that cloud feedbacks favor the persistence of SST anomalies in the tropics via the WES feedback. By detrending the cloud observations, we roughly removed the influence of greenhouse gases. However, we have not examined the possible role of aerosol-cloud interactions on driving phase shifts of the AMO [Booth et al., 2012], which remains an open question.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 20, 2017, 07:07:00 AM
Thanks for the links Jai.
Give me some time to read these papers.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 20, 2017, 07:52:07 AM
I read the Booth paper quickly and it does suggest that HADGEM2-ES explains a part (but not all) of the 'bump' in temperature in the 30's-40's. Also, I understand that their HADGEM2-ES run is mostly driven by indirect (not direct) aerosol forcing. If I understand that correctly, it makes assumptions about cloud coverage affected by aerosols.

Now I'm not sure yet how important their findings are, but I do see that this paper (Booth et al) draws criticism in the scientific literature.

For example, here, by Zhang et al 2012 responds to Booth et al :
Quote
However, here it is shown that there are major discrepancies between the HadGEM2-ES simulations and observations in the North Atlantic upper-ocean heat content, in the spatial pattern of multidecadal SST changes within and outside the North Atlantic, and in the subpolar North Atlantic sea surface salinity. These discrepancies may be strongly influenced by, and indeed in large part caused by, aerosol effects. It is also shown that the aerosol effects simulated in HadGEM2-ES cannot account for the observed anticorrelation between detrended multidecadal surface and subsurface temperature variations in the tropical North Atlantic. These discrepancies cast considerable doubt on the claim that aerosol forcing drives the bulk of this multidecadal
variability
.
http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-12-0331.1 (http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-12-0331.1)

Don't you just LOVE science and the scientific process ?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on April 20, 2017, 08:09:27 AM
I read the Booth paper quickly and it does suggest that HADGEM2-ES explains a part (but not all) of the 'bump' in temperature in the 30's-40's. Also, I understand that their HADGEM2-ES run is mostly driven by indirect (not direct) aerosol forcing. If I understand that correctly, it makes assumptions about cloud coverage affected by aerosols.

Now I'm not sure yet how important their findings are, but I do see that this paper (Booth et al) draws criticism in the scientific literature.

For example, here, by Zhang et al 2012 responds to Booth et al :
Quote
However, here it is shown that there are major discrepancies between the HadGEM2-ES simulations and observations in the North Atlantic upper-ocean heat content, in the spatial pattern of multidecadal SST changes within and outside the North Atlantic, and in the subpolar North Atlantic sea surface salinity. These discrepancies may be strongly influenced by, and indeed in large part caused by, aerosol effects. It is also shown that the aerosol effects simulated in HadGEM2-ES cannot account for the observed anticorrelation between detrended multidecadal surface and subsurface temperature variations in the tropical North Atlantic. These discrepancies cast considerable doubt on the claim that aerosol forcing drives the bulk of this multidecadal
variability
.

Don't you just LOVE science and the scientific process ?
Indeed; that said, it causes me to question somewhat the reference to that warming period as an indication of base-line "natural" increases driving Ding et. al.'s  conclusion, even if not responsible for *most* of the increase.

How would we eliminate human-sourced aerosols from baseline calculations of natural variability?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 20, 2017, 08:28:42 AM
Jai, your second paper (Bellomo et al 2016) seems to deal mostly with cloud effects over the tropics:

Quote
From these experiments we conclude that cloud feedbacks can account for 10% to 31% of the observed SST anomalies associated with the AMO over the tropics.

I'm not sure yet how much that has to do with aerosols and the 30's-40's temperature bump in the Arctic.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 20, 2017, 08:35:30 AM
Indeed; that said, it causes me to question somewhat the reference to that warming period as an indication of base-line "natural" increases driving Ding et. al.'s  conclusion, even if not responsible for *most* of the increase.

That is a good point, but please note that Ding et al 2017 does not take the temperature bump in the 30's and 40's as any form of 'base-line' for natural variability. In fact, they don't even mention it in the paper. Only Qinghua did in the comment section of this very forum.

In the paper, Ding et al 2017 uses a statistical method to 'tease out' the effect of 'atmospheric circulation', but in that process they knock out 65 % of the temperature trend (and trends in other variables) in the Arctic and assign it to 'atmospheric circulation'. And at attribution time, they do not compensate for any global warming (temperature) signal in these trends at all. Only 'high latitude winds'.

That's why I don't like Ding et al 2017. At all.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on April 20, 2017, 01:58:06 PM
Maybe it was a combination of AMO and lack of aerosols?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 20, 2017, 06:22:57 PM
Quote from: Rob Dekker on 4/18
Also, I find it interesting that on the ASIF Qinghua proposed a “70 year” cycle in the Arctic climate, although there is very little evidence to support that.

I doubt that the 30s-40s temperature bump had much to do with aerosols.
The AMO is a much more likely candidate.
After all, Delworth and Mann 2000 extracted (approx. 70 year) AMO cycles back 400 years from climate proxy data, including this one from the 30s-40s :

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 06:24:56 PM
Jai, your second paper (Bellomo et al 2016) seems to deal mostly with cloud effects over the tropics:

Quote
From these experiments we conclude that cloud feedbacks can account for 10% to 31% of the observed SST anomalies associated with the AMO over the tropics.

I'm not sure yet how much that has to do with aerosols and the 30's-40's temperature bump in the Arctic.

The Ding paper does not mention this bump because they assume that it is natural variability, as does the IPCC.

The translation of tropical circulation impacts in the arctic is the fundamental work of the paper.  There are also many other papers that indicate the linkage between aerosol emissions and tropical water vapor, high troposphere humidity, PDO, NAO and even AMOC circulation changes.  In addition, the sudden drop in sea levels at that time (1920-1928 see image below) also indicates a significant increase in tropical precipitation on land. 

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.climatewarmingcentral.com%2Fimages%2Fsea_levels.png&hash=b09b4b16fcb49349f7c810648e4904ef)

This paper from 2002

http://journals.ametsoc.org/doi/full/10.1175/1520-0442(2002)015%3C2103:TRTATI%3E2.0.CO%3B2 (http://journals.ametsoc.org/doi/full/10.1175/1520-0442(2002)015%3C2103:TRTATI%3E2.0.CO%3B2)

Quote
The present results, combined with this earlier finding, suggest that the indirect effects of anthropogenic sulfate may have contributed to the Sahelian drying trend. More generally, it is concluded that spatially varying aerosol-related forcing (both direct and indirect) can substantially alter low-latitude circulation and rainfall.

This paper in 2016

http://journals.ametsoc.org/doi/full/10.1175/JCLI-D-15-0174.1 (http://journals.ametsoc.org/doi/full/10.1175/JCLI-D-15-0174.1)

Quote
For the sstClimAerosol simulation, the cloud albedo effect contributes significantly to the changes in land surface temperature and precipitation pattern (Fig S6).

Note: TL in the image below shows changes in tropic land precipitation expected for a large increase in aerosols.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fjournals.ametsoc.org%2Fna101%2Fhome%2Fliteratum%2Fpublisher%2Fams%2Fjournals%2Fcontent%2Fclim%2F2016%2F15200442-29.2%2Fjcli-d-15-0174.1%2F20160108%2Fimages%2Flarge%2Fjcli-d-15-0174.1-f3.jpeg&hash=4057d4048b1001543a87c16f27698599)

Also attached image S6 from the supplementary information showing full aerosol modeling with extreme reductions in tropic land rainfall due to an increase in Aerosols (and by reason a large relative increase from a reduction in aerosols).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 06:37:51 PM
http://www.meteo.psu.edu/holocene/public_html/Mann/articles/articles/MannEtAlGRLPreprint.pdf (http://www.meteo.psu.edu/holocene/public_html/Mann/articles/articles/MannEtAlGRLPreprint.pdf)

Quote
For example, Mann and Emanuel [2006]
show that such a procedure misattributes at least part of the forced cooling of the NH
by anthropogenic aerosols during the 1950s-1970s (especially over parts of the North
Atlantic) to the purported down-swing of an internal “AMO” oscillation. A number of
climate modeling studies support their finding [Santer et al, 2006; Booth et al, 2012;
©2014 American Geophysical Union. All rights reserved.
Evan, 2012; Dunstone et al, 2013], though the precise role that anthropogenic
aerosols have played in recent decades continues to be debated in the literature [Koch
et al, 2011; Carslaw et al, 2013; Stevens, 2013].

When they detrended forcing for AMO oscillation using CMIP5 they used a model mean that largely did not include secondary cloud effects.

thus their AMO trend below still fits the anthropogenic aerosol emission curve very well.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 20, 2017, 07:27:57 PM
http://www.meteo.psu.edu/holocene/public_html/Mann/articles/articles/MannEtAlGRLPreprint.pdf (http://www.meteo.psu.edu/holocene/public_html/Mann/articles/articles/MannEtAlGRLPreprint.pdf)

When they detrended forcing for AMO oscillation using CMIP5 they used a model mean that largely did not include secondary cloud effects.

thus their AMO trend below still fits the anthropogenic aerosol emission curve very well.

Huh??

The "true AMO" graphs and the emissions graphs look nothing alike.  The timing and amplitude variances are completely different.

(https://tamino.files.wordpress.com/2010/08/sulf3.jpg)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fforum.arctic-sea-ice.net%2Findex.php%3Faction%3Ddlattach%3Btopic%3D1920.0%3Battach%3D44253%3Bimage&hash=1c894389bfa4be508e9d7291faf54803)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 20, 2017, 07:43:15 PM
Merging the emissions graph and Mann et al's "true AMO" graph yields:

(https://4.bp.blogspot.com/-lSk04xYBZGs/WPjyhifm1dI/AAAAAAAAAVw/ZFOxK-xX8ToPpTrEgU9RR63b4KaldJiwACLcB/s320/emiss%2B%252B%2Btrueamo.png)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 07:54:14 PM
Merging the emissions graph and Mann et al's "true AMO" graph yields:

(https://4.bp.blogspot.com/-lSk04xYBZGs/WPjyhifm1dI/AAAAAAAAAVw/ZFOxK-xX8ToPpTrEgU9RR63b4KaldJiwACLcB/s320/emiss%2B%252B%2Btrueamo.png)

Why do you suppose that the intensity of the 1930 change in aerosols would have the same effect in 1978?  The effect is driven by RELATIVE forcing compared to the GHG forcing component, not absolute.  In addition, the use of this graph must be framed within a dynamic fluid system that has inertia of forcing impacts  So the scale of the emissions is not as important as the breakpoints as shown below.

In addition, the AMOC curve is using multiple models to derive AMO from northern hemisphere temperature changes, there are average values that smooth the curve over decadal scales, so the break points are not clearly defined but it is clear that they fit the emission profile breakpoints very well (as do the other metrics that I posted above).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 20, 2017, 08:22:40 PM
(note: never mind, I see that you do not have a science education background)

Hmmm....I did attend MIT.  I do work as a metrologist.  Otherwise, spot on.

Please tell us the regression statistics.  You're just willy nilly drawing arbitrary lines and they really don't match up ..... or perhaps you're unable to.  Shoulld I do it for you - oh, wait, I don't have a science background. LOL.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 08:53:22 PM
my apologies
I thought you came from an MBA background and worked in manufacturing
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 09:14:18 PM
(note: never mind, I see that you do not have a science education background)

Please tell us the regression statistics. 

I already told you you have to adjust for relative forcing with impact of SO2 on tropical circulation (not simply a function of global forcing as regional impacts and high-altitude impacts appear to have much more weight).  This would be consistent with a simple model that shows relative impact of short-term aerosol emissions on the global system through the industrial period.  In addition, to accurately assess these impacts one would have to identify an overshoot effect from these short term changes based on the previous forcing history.  for example, shifts to positive AMO look to occur when SO2 emissions slow, revealing a strong signal that is being suppressed by aerosol emissions, however the break back to a negative AMO appears to happen quite suddenly when emissions begin to rise significantly - indicating a very large SO2 emission 'control knob' on the AMO function - as a function of relative forcing and energy imbalance and within a regional impact scale.

The lines are not arbitrary they are break points in both graphs and within the period of smoothing for the AMO using multiple models and Within the scale of emissions, they actually line up much better than I would expect.

for example, in the first graph, the 1920 line is actually 1917 (if you apply a grid function to determine the actual date instead of eyeballing it like I did)  and the 1935 graph line could reasonably be shifted to 1942 since this was when the emissions actually started to increase again (driving the shift in the AMO graph).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 20, 2017, 09:41:37 PM
for example, in the first graph, the 1920 line is actually 1917 (if you apply a grid function to determine the actual date instead of eyeballing it like I did)  and the 1935 graph line could reasonably be shifted to 1942 since this was when the emissions actually started to increase again (driving the shift in the AMO graph).

And since Mann et all detected a 70 yr cycle going back 400 years are you really serious or just so tied into a pet theory that you can't see the silliness of it??

Besides how is it we don't see a change when MT Agung or MT Pinatubo erupted?  Is this only forced by anthropogenic aerosols and ignores natural emissions??  Funny how the atoms and molecules must be zipping around with little origin tags on them.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 09:51:45 PM
for example, in the first graph, the 1920 line is actually 1917 (if you apply a grid function to determine the actual date instead of eyeballing it like I did)  and the 1935 graph line could reasonably be shifted to 1942 since this was when the emissions actually started to increase again (driving the shift in the AMO graph).


Besides how is it we don't see a change when MT Agung or MT Pinatubo erupted? 


Rainfall and cloud patterns are a Tropospheric loading effect with larger impacts from upper troposphere loading.  Stratospheric impacts act more like GHG.  What can you tell me about secondary cloud effects of tropospheric aerosols?

Actual AMO series below:

https://www.esrl.noaa.gov/psd/data/correlation/amon.us.long.data (https://www.esrl.noaa.gov/psd/data/correlation/amon.us.long.data)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 20, 2017, 09:52:18 PM
jai - another factor you've completely ignored is the completely different spatial/geographical distributions; high emissions in the early and mid-20th century would have been from Eurpope and North America. In recent decades those areas have seen reduced emissions while Asia/China have greatly accelerated.  Expecting the same forcing patter from completely different geographical distributions would seem a bit over-reaching - to put it charitably.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 20, 2017, 10:00:11 PM
jai - another factor you've completely ignored is the completely different spatial/geographical distributions; high emissions in the early and mid-20th century would have been from Eurpope and North America. In recent decades those areas have seen reduced emissions while Asia/China have greatly accelerated.  Expecting the same forcing patter from completely different geographical distributions would seem a bit over-reaching - to put it charitably.

why don't you quote me where I did this.

wrt Mann's 70 year AMO cycle analysis is this the paper you refer to?  perhaps you want to back up your assertions with credible links to peer reviewed papers as I have?

https://pdfs.semanticscholar.org/24e9/6c16772d5d38dd1f0e759514fc6d2523dc1c.pdf
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: ktonine on April 20, 2017, 10:32:56 PM
wrt Mann's 70 year AMO cycle analysis is this the paper you refer to?  perhaps you want to back up your assertions with credible links to peer reviewed papers as I have?

https://pdfs.semanticscholar.org/24e9/6c16772d5d38dd1f0e759514fc6d2523dc1c.pdf (https://pdfs.semanticscholar.org/24e9/6c16772d5d38dd1f0e759514fc6d2523dc1c.pdf)

The Mann paper was already previously cited upthread with link.

And actually the record now goes back over 600 years: Amplification of the Atlantic Multidecadal Oscillation associated with the onset of the industrial-era warming (https://www.nature.com/articles/srep40861?WT.feed_name=subjects_palaeoclimate), G. W. K. Moore, J. Halfar, H. Majeed, W. Adey & A. Kronz, 2017

Quote
The reconstruction that captures the centennial timescale variability explains ~25% of the variance in the time series (Fig. 3a). The mode has a local maximum during the 15th century that was followed by an ~400 year period of near constant values that ended in the early part of the 19th century after which there was a trend towards higher values. Indeed, values in the late 20th century were the highest over the 643-year long record. This behaviour is broadly consistent with the piecewise linear fit to the time series shown in Fig. 1.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 21, 2017, 12:05:35 AM
so basically, your contention of there not being a significant aerosol component to the 1930's trend is justified by the following long-series?

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: nukefix on April 21, 2017, 12:43:11 AM
Interesting, does the AMO-reconstruction show the abrupt end of the LIA, or something else?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Rob Dekker on April 21, 2017, 03:57:05 AM
Quote from: Rob Dekker on 4/18
Also, I find it interesting that on the ASIF Qinghua proposed a “70 year” cycle in the Arctic climate, although there is very little evidence to support that.

I doubt that the 30s-40s temperature bump had much to do with aerosols.
The AMO is a much more likely candidate.
After all, Delworth and Mann 2000 extracted (approx. 70 year) AMO cycles back 400 years from climate proxy data, including this one from the 30s-40s :

Yeah. That kind of did not come out the way I wanted and requires some explanation :D

The first comment was in response to Qinghua's statements suggesting a 70 year cycle that originated in "atmospheric circulation" and is significant enough to explain a large part of the recent multi-decadal ice decline (50% in his paper). The same sort of significance that Qinghua uses to predict that the real big melt will be 50 - 100 years from now. And the same sort of significance that Qinghua believes there was in the 30's and 40's.

What I wanted to point out is that there is no evidence for such a strong signal.

There only is the AMO, a 70 year cycle which has a very limited effect on NH warming (about 0.1 C as Mann pointed out; with 0.4 C in the Northern Atlantic, maybe a bit more in the Arctic) and a limited effect on sea ice retreat as Walsh pointed out for the 30's-40's period, and as Kinnard et al 2011 showed in the reconstruction of 1450 years of Arctic sea ice.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: bbr2314 on April 21, 2017, 04:28:50 AM
for example, in the first graph, the 1920 line is actually 1917 (if you apply a grid function to determine the actual date instead of eyeballing it like I did)  and the 1935 graph line could reasonably be shifted to 1942 since this was when the emissions actually started to increase again (driving the shift in the AMO graph).

And since Mann et all detected a 70 yr cycle going back 400 years are you really serious or just so tied into a pet theory that you can't see the silliness of it??

Besides how is it we don't see a change when MT Agung or MT Pinatubo erupted?  Is this only forced by anthropogenic aerosols and ignores natural emissions??  Funny how the atoms and molecules must be zipping around with little origin tags on them.
https://en.wikipedia.org/wiki/Kondratiev_wave
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 21, 2017, 07:02:52 AM
u know bbr that was my first thought too but realized it would be impossible to show that the economic cycle drove the emission trend or if the temperature trend drove the economic cycle.  (I suspect the former)  It is interesting though that the KWave has shifted to a longer period than in the 1800s ( it used to be a 50 year cycle.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: bbr2314 on April 21, 2017, 07:54:01 AM
u know bbr that was my first thought too but realized it would be impossible to show that the economic cycle drove the emission trend or if the temperature trend drove the economic cycle.  (I suspect the former)  It is interesting though that the KWave has shifted to a longer period than in the 1800s ( it used to be a 50 year cycle.
I would think it is most definitely that economic cycles drive emission trends. I think this began with the dawn of agriculture, when albedo feedbacks (as well as primitive emissions) would have started the see-saw that continues to this day, where economic prosperity drives climactic changes, which demand innovation & economic re-organization (i.e. periods of recession/depression), and then the cycle continues.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 21, 2017, 05:14:22 PM
It would be very difficult to expect an aerosol forcing component in the historical trend based on agricultural cycles.

however

there is more than a number of papers that have determined that the late period cycle could (Edit:) NOT be driven by natural variability without a strong aerosol cloud effect in the tropics.

for example:

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071337/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2016GL071337/abstract)

Quote
we conclude that models need external forcing to explain the magnitude, timing, and apparent multidecadal frequency of the observed twentieth century AMO variability.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: bbr2314 on April 21, 2017, 06:01:49 PM
It would be very difficult to expect an aerosol forcing component in the historical trend based on agricultural cycles.

however

there is more than a number of papers that have determined that the late period cycle could be driven by natural variability without a strong aerosol cloud effect in the tropics.

for example:

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071337/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2016GL071337/abstract)

Quote
we conclude that models need external forcing to explain the magnitude, timing, and apparent multidecadal frequency of the observed twentieth century AMO variability.
Well, aerosols would not have been the primary driver initially, it would have been albedo changes (forest -> cropland over the Middle East, Eastern Asia, Southern Europe, and parts of the Americas).

Perhaps slash and burn techniques would have contributed some token amount of aerosols, but that does not mean that temperature trends/climactic variability were not impacted, creating the initial see-saw mechanism that persists to this day.

I would think that aerosols further amplified the existing changes as primitive industrialization began ~4000-3000BC (look at the Pyramids!) with corresponding heavy industry that was very inefficient in terms of raw materials -> output (which pushed large amounts of aerosols into the atmosphere). This peaked with the Romans & Chinese in the first millennium AD, with those numbers only reached again ~1800-1850. While raw output may have been higher post-1800, emissions were still roughly equivalent until about 200 years ago due to the dirtiness of industry way back when.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on April 21, 2017, 06:18:46 PM
please see my edit above:

It is impossible to determine these things without a strong explanation of the scale of early ag emission cycles.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Neven on May 31, 2017, 01:16:28 PM
I saw this article (https://phys.org/news/2017-05-uncover-early-20th-century-arctic.html) today on Phys.org that reminded me of this thread:

Quote
Researchers uncover a cause for early 20th century Arctic warming

Is a warmer Arctic a canary of global warming? Since the 1970s the northern polar region has warmed faster than global averages by a factor or two or more, in a process of 'Arctic amplification' which is linked to a drastic reduction in sea ice.

But then how to explain a similar rapid warming that occurred during the early 20th century, when the effects of greenhouse gases were considerably weaker than today? And what can we prove about the period, given the scarcity of usable data and observations prior to the 1950s?

Now scientists from Kyoto University and UC San Diego have discovered that this phenomenon occurred when the warming phase—'interdecadal variability mode'—of both the Pacific and Atlantic Oceans coincided. The team's findings appeared recently in the journal PNAS.

"We found that early 20th century sea surface temperatures in the tropical Pacific and North Atlantic had warmed much more than previously thought," explains lead author Hiroki Tokinaga of Kyoto.

"Using observations and model simulations, we've demonstrated that rising Pacific-Atlantic temperatures were the major driver of rapid Arctic warming in the early 20th century."

Previous explanations for early Arctic warming have including decreased volcanic aerosols and increased solar radiation, but none of these have been able to simulate observed conditions from the period.

Tokinaga's team found that when the interdecadal rise in sea surface temperatures was included in simulation calculations, the results properly reflected early Arctic conditions.

"Coupled ocean-atmosphere simulations also support the intensification of Arctic warming," continues Shang-Ping Xie of UCSD, "which was caused by a concurrent, cold-to-warm phase shift of Pacific and Atlantic interdecadal modes."

The researchers explain that these new findings can help constrain model climate projections over the Arctic region.

"It is likely that temperatures in the Arctic will continue to rise due to anthropogenic global warming," concludes Tokinaga. "Our study does not deny this. We are rather suggesting that Arctic warming could accelerate or decelerate due to internal variability of the Pacific and the Atlantic."

"It is a challenge to accurately predict when the next big swing of multidecadal variability will occur. Careful monitoring is essential, given the enormous impact on the Arctic climate."

Obviously the same Atlantic-Pacific simultaneous interdecadal variability mode hasn't been positive in the past 30-40 years, or we'd be hearing all about it. So, what happens when it does go positive?

Sorry, rhetorical question.  ;)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: epiphyte on June 02, 2017, 06:36:39 AM

The most intriguing part of that event is that warming exhibited a pretty large scale feature in the Arctic and the area was warmed by something very fast from 1920s to 1930s.  So causes  of this fast warming rate has puzzled me for a long time.

Reduction in global SO2 emissions


So the early 20th-Century UK initiatives to clean up the "Dark, Satanic Mills" and to banish the London "smog" could now be interpreted as having unintended consequences?

Don't let the Dirty-Coal lobby get wind of that one. Next thing you know DT will be tweeting that the librul tree-huggers _caused_ global warming.



Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Pmt111500 on June 02, 2017, 07:04:32 AM

The most intriguing part of that event is that warming exhibited a pretty large scale feature in the Arctic and the area was warmed by something very fast from 1920s to 1930s.  So causes  of this fast warming rate has puzzled me for a long time.

Reduction in global SO2 emissions


So the early 20th-Century UK initiatives to clean up the "Dark, Satanic Mills" and to banish the London "smog" could now be interpreted as having unintended consequences?

Don't let the Dirty-Coal lobby get wind of that one. Next thing you know DT will be tweeting that the librul tree-huggers _caused_ global warming.

I thought the coal-lobbyists lead by US government already did this? At least I've seen some comments claiming this. The best way to attack these assholes would be to pour sulfuric and nitrous acids to their yards and spray their houses with the stuff as they want the good old 1970s back, but as this is still illegal, we'd need to find something else for these asshats. Severe their US made cars and Ddos attack their servers? Still illegal, but less conspicuous.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Ice Shieldz on June 02, 2017, 07:26:15 AM
This is fitting given current events
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Jim Pettit on June 02, 2017, 01:05:41 PM
Guys, I completely agree with your comments--but please be mindful of the thread you're in, and try to stay on topic. Thanks!
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on June 02, 2017, 08:43:39 PM
I saw this article (https://phys.org/news/2017-05-uncover-early-20th-century-arctic.html) today on Phys.org that reminded me of this thread:



And I saw your thread post and it reminded me of this article ;-)

onlinelibrary.wiley.com/doi/10.1002/2017GL073480/full

Trajectories toward the 1.5°C Paris target: Modulation by the Interdecadal Pacific Oscillation

article here:
https://www.theguardian.com/environment/planet-oz/2017/may/09/planet-could-breach-15c-warming-limit-within-10-years-but-be-aware-of-caveats (https://www.theguardian.com/environment/planet-oz/2017/may/09/planet-could-breach-15c-warming-limit-within-10-years-but-be-aware-of-caveats)

Planet could breach 1.5C warming limit within 10 years, but be aware of caveats

Quote
But new research published in a leading scientific journal suggests that just eight years after that report is published, the world might have already reached that 1.5C target – or at least one definition of it (some senior scientists disagree with some of the assumptions in the paper – read on for those important caveats).


Global warming 'hiatus' doesn't change long term climate predictions – study
Published in the journal Geophysical Research Letters, the research looks closely at the influence of a mechanism in the climate known as the Interdecadal Pacific Oscillation (IPO).

“The IPO is like the long-term version of El Niño – it’s like El Niño’s uncle,” says Ben Henley of the University of Melbourne and the research’s lead author.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Iceismylife on March 24, 2018, 12:44:35 AM
nice thread. I will read it through and through.  This comment is just so I can find it again.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: FishOutofWater on March 24, 2018, 03:38:54 PM
Neven & folks, there is a potential weakness in the reasoning above in that interesting paper about early 20th century Arctic warming. That warming was apparently brought on naturally by concurrent warm phases in the north Atlantic and north Pacific. But they do not eliminate the possibility that human caused GHG forcing could bring on concurrent warmth in the north Atlantic and north Pacific. There was a period in the 1960's when sulfate aerosols cooled the north Atlantic masking the effects of increasing GHGs. Now aerosol levels are high above the seas near China and India.

Because the southern hemisphere has a continent at the pole surrounded by the vast southern ocean it will tend to warm more slowly than the north after a positive forcing event because the Antarctic Circumpolar Current prevents warm subtropical water from getting close to the continent at any place other than the Antarctic peninsula.  Gulf stream water, however gets into the Arctic ocean at 300m to 600m depth. And Rossby wave teleconnections cause atmospheric heating in the Arctic when the equatorial west Pacific gets warmer than normal and has very strong convection like it did this NH winter.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Steven on November 05, 2018, 07:41:42 PM
New paper by Ding et al.:

Fingerprints of internal drivers of Arctic sea ice loss in observations and model simulations

https://www.nature.com/articles/s41561-018-0256-8


Abstract:
Quote
The relative contribution and physical drivers of internal variability in recent Arctic sea ice loss remain open questions, leaving up for debate whether global climate models used for climate projection lack sufficient sensitivity in the Arctic to climate forcing.  Here, through analysis of large ensembles of fully coupled climate model simulations with historical radiative forcing, we present an important internal mechanism arising from low-frequency Arctic atmospheric variability in models that can cause substantial summer sea ice melting in addition to that due to anthropogenic forcing. 

This simulated internal variability shows a strong similarity to the observed Arctic atmospheric change in the past 37 years.  Through a fingerprint pattern matching method, we estimate that this internal variability contributes to about 40–50% of observed multi-decadal decline in Arctic sea ice.

Our study also suggests that global climate models may not actually underestimate sea ice sensitivities in the Arctic, but have trouble fully replicating an observed linkage between the Arctic and lower latitudes in recent decades.  Further improvements in simulating the observed Arctic–global linkage are thus necessary before the Arctic’s sensitivity to global warming in models can be quantified with confidence.

Paper is paywalled, but the full text can also be found at sci-hub (https://sci-hub.tw/https://doi.org/10.1038/s41561-018-0256-8#).
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on November 05, 2018, 11:55:00 PM
I'm going to need to read that.  I have a hard time swallowing that 40-50% figure.  I'd like to see supporting evidence from historical data and physical evidence suggesting cycles tied to a driving mechanism.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Richard Rathbone on November 06, 2018, 01:10:38 PM
Looks good to me. The "hiatus" in Sept extent since 2012 has some time to run yet. It would be interesting to know if there are similar things going on in other seasons and whether they correlate e.g. if we can expect a continuing run of winter records but no summer records, but they've only done the analysis for the summer weather and September extent.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on November 06, 2018, 02:32:59 PM
It is incredibly distressing to me to see the author use "arctic sea ice" and "arctic sea ice area" interchangeably. Arctic sea ice area or extent are terribly important measures, but they DO NOT measure the ice in the arctic, only the surface area the ice occupies. Sea ice is frozen sea water, a 3 dimensional object.

When the author says 50% of the current losses are due to "internal variability", how does he determined if internal variability changed due to climate change?

Does this mean he expects a 50% recovery soon? When does this "natural cycle ends"?

Also, what's up with figure 1.E? Why are the models way below observations during the earlier decades and then match observations in the recent decades?

I think the intentions of the author are very good, and I wouldn't dare to challenge the math, but I also think that some necesary assumptions for this analysis are wrong, in particular using sea ice area as proxy for sea ice and calling random variability "natural" when the variability itself probably changed and will change more as the climate changes.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Richard Rathbone on November 06, 2018, 06:03:28 PM
It is incredibly distressing to me to see the author use "arctic sea ice" and "arctic sea ice area" interchangeably. Arctic sea ice area or extent are terribly important measures, but they DO NOT measure the ice in the arctic, only the surface area the ice occupies. Sea ice is frozen sea water, a 3 dimensional object.

When the author says 50% of the current losses are due to "internal variability", how does he determined if internal variability changed due to climate change?

Does this mean he expects a 50% recovery soon? When does this "natural cycle ends"?

Also, what's up with figure 1.E? Why are the models way below observations during the earlier decades and then match observations in the recent decades?

I think the intentions of the author are very good, and I wouldn't dare to challenge the math, but I also think that some necesary assumptions for this analysis are wrong, in particular using sea ice area as proxy for sea ice and calling random variability "natural" when the variability itself probably changed and will change more as the climate changes.

The various mentions of sea ice and sea ice area almost always refer to Sept extent.

The fingerprinting is how the variability is attributed. The same fingerprint is seen in the control runs as the runs under historical forcing and the historical observations. The same fingerprint in all 3 is good evidence that the mechanism of the variability hasn't changed much and that much of the Sept 2012 record can be attributed to it.

The models bounce all over the place in 1e because internal variability is high. The increasing spread of the grey area with time does suggest that the variability has increased, but the fingerprint correspondences are good evidence that the models are representing it decently.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on November 06, 2018, 08:43:36 PM
Continuing Archmid's thought, the paper in contrast highlights the view some of us have, which is volume rather than extent and area is the key metric for ice and by extension, arctic system "health".

Area and extent both will become far more volatile as volume decreases.

As such,  they will become far less useful metrics to use in assessing the state of the system, or for skillfully determine change and direction in the system.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on November 06, 2018, 10:12:25 PM
Thanks for the answers. They bring clarity and more questions.

Quote
The various mentions of sea ice and sea ice area almost always refer to Sept extent.

Yeah, this is common practice in most climate papers I've read and maybe even in ASIF. I'm probably guilty of it on occasion.  It is distressing to me because area is such an incomplete measure. Area and extent seems like pillars of ASI science when volume with shape information should be the pillar. I understand that volume is a much more difficult measure and area has  larger, more agile set, but still. I believe it is wrong to use them as equivalent because it may lead to fundamental mistakes in the science.

Quote
The fingerprinting is how the variability is attributed. The same fingerprint is seen in the control runs as the runs under historical forcing and the historical observations.

This is what the paper says about the fingerprint:

Quote
Internal variability is determined from a long (1,800 years) control run of CESM1 with constant pre-industrial forcing (‘PI’ hereafter), as well as by the deviations of each ensemble member in 40-Forced from the ensemble mean.

 After re-reading the paper (and failing to fully comprehend it) my questions increased.

This is my understanding of the experiment. They take a series of models, run them and calculate mean ASI area loss as a result of forcing. The ensamble (a sort of mean of the models) under predict the ASI area lost. Thus the difference between the ensemble and the observations must be "internal" variability.

I can agree with that if two assumptions hold. The author is beholden to the truth enough ( gotta love science) to say it more clearly than I could:

Quote
This approach makes the assumption that sea ice sensitivity can be observed without contamination by internal variability and that models appropriately capture the linkage between Arctic sea ice loss and global temperatures.

I'm convinced that neither of these assumptions hold, but that is based on my mental model of the Arctic. I will know over the next few years. If the Arctic recovers then it was internal variability. If it doesn't then we are in deep trouble.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Richard Rathbone on November 06, 2018, 11:24:01 PM
Thanks for the answers. They bring clarity and more questions.


This is what the paper says about the fingerprint:

Quote
Internal variability is determined from a long (1,800 years) control run of CESM1 with constant pre-industrial forcing (‘PI’ hereafter), as well as by the deviations of each ensemble member in 40-Forced from the ensemble mean.

 After re-reading the paper (and failing to fully comprehend it) my questions increased.

This is my understanding of the experiment. They take a series of models, run them and calculate mean ASI area loss as a result of forcing. The ensamble (a sort of mean of the models) under predict the ASI area lost. Thus the difference between the ensemble and the observations must be "internal" variability.



The fingerprint is the particular pressure pattern in the Arctic summer in high loss years and the weather patterns that connect it to particular temperature variations in the Pacific. The same pattern is seen in the control run, and the historically forced runs and the data.

The internal variability isn't the difference between the historical data and the ensemble mean, its the spread of the ensemble. Look at the band of grey lines in 1e. The internal variability is the difference between the top of that band and the bottom of that band.

There's not enough historic data to pull the variability from it alone. Thats one of the key points from this paper. In 30 years time it might be possible to assess the variability from the historic data, but the record is still too short to properly characterise the climate.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: gerontocrat on November 06, 2018, 11:46:52 PM

Quote
The various mentions of sea ice and sea ice area almost always refer to Sept extent.

I understand that volume is a much more difficult measure and area has  larger, more agile set, but still. I believe it is wrong to use them as equivalent because it may lead to fundamental mistakes in the science.
I believe that concentrating on minimum (just one day in the year) is not good enough.

Area to me is very important as the less area of ice there is means the greater area of open water with consequent major change to the climate / weather where it is happening. How one distinguishes a "natural variation" from a feedback from climate change caused by an icy sea becoming an open water sea I have not the foggiest idea.

That is why I developed an analysis of open water vs sea ice for each of the 14 seas to track the change in each sea (1980 to 2018) from icy deserts to maritime open ocean at various periods of the year and the entire year. I think I will give them another airing on the sea ice extent thread sometime this month and definitely at the year end.

Volume alone surely also is not the answer, as volume is thickness x the area covered, and loss of area surely changes the climate ?

It's late, my brain is on strike.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: oren on November 07, 2018, 03:11:04 AM
I've read it, it's an impressive piece but I am not very convinced of the bottom line. I doubt the system can be modeled effectively enough to draw such conclusions.
A few questions floated in mind as I read:
* Do we expect sea ice to recover nearly 50% of the loss since 1979 when the JJA200 high pressure flips to low pressure? I personally find it very hard to believe.
* How often does this pressure regime flip occur in the control simulations? How long does it last?
* Can the models replicate winter sea ice reduction as has been occurring in the last few years (lower max)? I agree with gerontocrat that focusing on one day of the year is not enough.
* Can the models replicate volume loss and strong reduction of older MYI? Do the models go down to such level of detail?
* I notice that the area data used was up to 2015. But in 2016 there was another very low point of sea ice area at min. Does 2016 fit the pressure pattern of the study?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Richard Rathbone on November 07, 2018, 01:59:56 PM
I've read it, it's an impressive piece but I am not very convinced of the bottom line. I doubt the system can be modeled effectively enough to draw such conclusions.
A few questions floated in mind as I read:
* Do we expect sea ice to recover nearly 50% of the loss since 1979 when the JJA200 high pressure flips to low pressure? I personally find it very hard to believe.
* How often does this pressure regime flip occur in the control simulations? How long does it last?
* Can the models replicate winter sea ice reduction as has been occurring in the last few years (lower max)? I agree with gerontocrat that focusing on one day of the year is not enough.
* Can the models replicate volume loss and strong reduction of older MYI? Do the models go down to such level of detail?
* I notice that the area data used was up to 2015. But in 2016 there was another very low point of sea ice area at min. Does 2016 fit the pressure pattern of the study?

It already has. Check what happened between 2012 and 2013.
The earlier paper claims a 70 year oscillation, the current one merely that 30 years of data can
 have seriously biassed trends in it. That could be due to a 70 year oscillation, but they don't make the case that it is.
2016 was still higher than 2007 and there's a decade of trend between them too.
These models can't replicate anything on a timescale of a few years. This paper says 60 years of data is needed before you can get decently reliable results from it and that if you look at shorter timescales the internal variability is quite likely to be fooling you.
Volume is in the models, but they aren't all that good at extent, let alone volume. This paper has good evidence for the ensemble spread being down to real variability on long timescales, but the ensemble mean still has significant bias in it. (that bias is why the left and right hand scales on 1e are offset, the match with observations isn't as good as it looks if you don't notice the bias has been removed in that figure)
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jdallen on November 08, 2018, 07:37:15 AM
Jim Pettit's graph and data from the UW applied physics laboratory summarizes my difficulty accepting the author's conclusions:

http://iwantsomeproof.com/extimg/siv_annual_max_loss_and_ice_remaining.png

Can we find *any* pre-industrial evidence to suggest built-in variability dropped volume to near or under 10,000KM3 and then returned it to greater than 15,000KM3 at summer minimum?

Also contributing... The changes that have taken place in the last 20 years have dramatically altered the system's dynamics.  The energy mechanics of 1980 are nothing like those in 2000 which are nothing like those now.  How can you comfortably attribute 50% of system variability to "natural" variability when the fundamental mechanics of the system itself have changed?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Richard Rathbone on November 09, 2018, 01:43:36 PM
Jim Pettit's graph and data from the UW applied physics laboratory summarizes my difficulty accepting the author's conclusions:

http://iwantsomeproof.com/extimg/siv_annual_max_loss_and_ice_remaining.png

Can we find *any* pre-industrial evidence to suggest built-in variability dropped volume to near or under 10,000KM3 and then returned it to greater than 15,000KM3 at summer minimum?

Also contributing... The changes that have taken place in the last 20 years have dramatically altered the system's dynamics.  The energy mechanics of 1980 are nothing like those in 2000 which are nothing like those now.  How can you comfortably attribute 50% of system variability to "natural" variability when the fundamental mechanics of the system itself have changed?

We know full well that extent and volume have behaved differently during the historical period. This paper provides strong evidence that conclusions drawn from a data span as short as the historical period are biassed. A plot of volume from the historical period only is doubly biassed, first because the period considered is too short to capture the range of variability and second because its volume rather than extent.

The fundamental mechanics haven't changed. Heat is still being transferred by radiation, conduction and convection. Ice still melts and water freezes according to imbalances in energy transfer at the phase interfaces. Air and water are still moving in response to pressure gradients. The Navier Stokes equation is as valid then as it is now.

The way ice moves in response to the stresses exerted on it by air and water is not well understood and its quite possible that the equations used for it and the parameters fitted to them work better in an Arctic dominated by MYI, but its also possible they work better in an Arctic dominated by FYI and the models are actually representing that aspect better.

There's strong evidence in this paper that the high melt years in 2007-2012 are at the extremes of melt below the trend and 2013 is on trend, and the reason that isn't obvious from the historical record is that the historical record is too short.

We have a historical temperature record with multiple El-Ninos in it so its obvious when a misleading trend line is drawn in it by picking El-Nino/La Nina endpoints. If we only had one half of an ENSO period in the historical data it would be extremely difficult to get a reliable trend from it. Thats the situation we are in with regard to ice extent in the Arctic. The historical period is too short and trends in it are liable to substantial bias.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on November 10, 2018, 03:27:26 PM

The fingerprint is the particular pressure pattern in the Arctic summer in high loss years and the weather patterns that connect it to particular temperature variations in the Pacific. The same pattern is seen in the control run, and the historically forced runs and the data. 

To be clear, FTA:

Quote
The mechanisms of this teleconnection appear to be similar in observations and models, but the specific source areas and path of wave activity underlying the establishment of the high pressure in the Arctic are displaced in the model.

That important caveat, combined with the failure of most of the model runs to account for the Arctic loses tell me that

Quote
The internal variability isn't the difference between the historical data and the ensemble mean, its the spread of the ensemble. Look at the band of grey lines in 1e. The internal variability is the difference between the top of that band and the bottom of that band.


To me this says that if the Models are sufficiently accurate representations of the system, then the variability is given by the spread of the models. The problem is that the models have significant difference with observations. They are not sufficiently good representations of the system. I think the paper does a fantastic job illustrating the big differences between the models and the observations. Fig. 4 is particularly interesting.


Quote
There's not enough historic data to pull the variability from it alone. That's one of the key points from this paper. In 30 years time it might be possible to assess the variability from the historic data, but the record is still too short to properly characterize the climate.

I agree with that. There is statistical uncertainty due to the short record. Luckily, mathematical statistics are not the only tool we have to inform our decision making process. We have physics that dictate that the warming will continue and will increase. There is every reason to believe that "internal variability" will vary as the climate changes.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on November 10, 2018, 04:16:57 PM
We know full well that extent and volume have behaved differently during the historical period. This paper provides strong evidence that conclusions drawn from a data span as short as the historical period are biassed. A plot of volume from the historical period only is doubly biassed, first because the period considered is too short to capture the range of variability and second because its volume rather than extent.

I think this is a good argument only without context. If we knew nothing about the past temperatures and conditions of the Arctic and the world, then yes, a mere volume plot would be doubly biased. But we do know quite a bit about the state of the Arctic for much longer time frames than 37 years. There is every reason to expect that it was very cold, central volume and area was much less variable. There is every reason to expect multiyear ice to dominate the Arctic for thousands of years.

Quote
The fundamental mechanics haven't changed. Heat is still being transferred by radiation, conduction and convection. Ice still melts and water freezes according to imbalances in energy transfer at the phase interfaces. Air and water are still moving in response to pressure gradients. The Navier Stokes equation is as valid then as it is now.

True, but all values in the fundamental mechanics are changing. Some of them are bounded by fundamental physics and some of them are bounded by changing conditions and phenomena. As these values change, the models diverge from observations.

Quote
The way ice moves in response to the stresses exerted on it by air and water is not well understood and its quite possible that the equations used for it and the parameters fitted to them work better in an Arctic dominated by MYI, but its also possible they work better in an Arctic dominated by FYI and the models are actually representing that aspect better.

I doubt it. For example, the models were created for a desert climate but the arctic is changing to a maritime climate. The models will need some extreme luck for changes in atmospheric and oceanic pattern that this climate change is bringing to result in better accuracy. New models can bring better accuracy. But if they show near term destruction, who is going to believe them?

Quote
There's strong evidence in this paper that the high melt years in 2007-2012 are at the extremes of melt below the trend and 2013 is on trend, and the reason that isn't obvious from the historical record is that the historical record is too short.

You must forgive my insistence, but this is so unbelievable. When one considers the changes in    thickness/volume it becomes even more unbelievable. I just think about the changes in ice  behaviors around the Bering and Chukchi and I admit I start getting emotional because the danger is so real. Let's not even mention the changes North of Svalbard.

2012 was obviously below the trend, but 2013 was not "on-trend". More likely that 2013  was a rebound year, literally caused by the 2012 ice loss. The mechanism being that in 2012 the Arctic ocean was colder. When it lost the ice cover for the first time in millennia the ocean gained a lot of heat and the atmosphere lost a lot of heat, creating perfect conditions for mass freezing. That massive freezing ceased as heat/salinity changes started having a greater impact. That heat keeps accumulating resulting in increasingly hot winters.

The physical basis for the 2013 refreeze and the behavior during the following years should be used to inform weak statistics.

Quote
We have a historical temperature record with multiple El-Ninos in it so its obvious when a misleading trend line is drawn in it by picking El-Nino/La Nina endpoints. If we only had one half of an ENSO period in the historical data it would be extremely difficult to get a reliable trend from it. Thats the situation we are in with regard to ice extent in the Arctic. The historical period is too short and trends in it are liable to substantial bias.

Context. Arctic average Temperatures since 1900

http://berkeleyearth.org/wp-content/uploads/2018/01/Arctic2017.png

Why would you expect for the ice to comeback or 2013 be on trend when temperature is way above trend? Isn't it more likely that the models are missing huge elements of a changing climate?
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Archimid on November 10, 2018, 05:14:09 PM

The fingerprint is the particular pressure pattern in the Arctic summer in high loss years and the weather patterns that connect it to particular temperature variations in the Pacific. The same pattern is seen in the control run, and the historically forced runs and the data. 

To be clear, FTA:

Quote
The mechanisms of this teleconnection appear to be similar in observations and models, but the specific source areas and path of wave activity underlying the establishment of the high pressure in the Arctic are displaced in the model.

That important caveat, combined with the failure of most of the model runs to account for the Arctic loses tell me that the models are likely wrong.

Quote
The internal variability isn't the difference between the historical data and the ensemble mean, its the spread of the ensemble. Look at the band of grey lines in 1e. The internal variability is the difference between the top of that band and the bottom of that band.


To me this says that if the Models are sufficiently accurate representations of the system, then the variability is given by the spread of the models. The problem is that the models have significant difference with observations. They are not sufficiently good representations of the system. I think the paper does a fantastic job illustrating the big differences between the models and the observations. Fig. 4 is particularly interesting.


Quote
There's not enough historic data to pull the variability from it alone. That's one of the key points from this paper. In 30 years time it might be possible to assess the variability from the historic data, but the record is still too short to properly characterize the climate.

I agree with that. There is statistical uncertainty due to the short record. Luckily, mathematical statistics are not the only tool we have to inform our decision making process. We have physics that dictate that the warming will continue and will increase. There is every reason to believe that "internal variability" will vary as the climate changes.
Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: jai mitchell on June 20, 2019, 11:24:00 PM
This lecture by Dr Charles Kennel Prof. Emeritus from Scripps discusses their paper currently under review in PNAS that correlates Arctic sea ice loss, East Siberian September Convection and the translation connection to 300 mb surface flows including increasing 'super strong' trade winds during December following the sea ice loss years.

This shows that the sea ice loss is the tail wagging the dog (ENSO) as opposed to the idea from the paper started in this thread, that 'natural variability' drove the ice loss.

https://www.youtube.com/watch?v=_b6k7lWOA6Y&t=32m56s

Started midway into lecture as he is discussing the findings.  I do recommend watching from the beginning though.

Title: Re: Arctic sea ice changes: Natural variation vs human influence
Post by: Richard Rathbone on June 22, 2019, 03:39:11 PM
I'd really need to see the final version of the paper, but at the moment this looks like another part of the same picture, not a different picture to me.

Pacific influences arctic in spring-summer, arctic influences pacific in autumn-winter, and that feedback loop powers multi-decadal variability.