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/)QuoteAll 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.
"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.
“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
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.
BTW, thanks a lot for opening this separate thread, Archimid!
3 links
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,
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?
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?
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): But misfit relative to CMIP5 mean doesn't imply internal variability! CMIP5 mean likely does NOT capture true forced trend.
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.
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?
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.
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
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
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
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).
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...
Is it possible that a paid denier could infiltrate a group of otherwise solid scientists with the purpose of such wording.
"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."
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.
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.
...
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.
jdallenI think that that is the big question. I've only seen the abstract, so perhaps the full paper explains this better.
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've only seen the abstract, so perhaps the full paper explains this better.
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
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).
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?
That said, it wouldn't be the first time an academic published his findings without considering the implications in a larger world.
QuoteThat 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 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.QuoteThat 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.
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...
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.
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...
I find this coincidence highly improbable.
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:
tzupanic, thanks for the paper. Here is a quote from the paper:QuoteHaving 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.
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.
...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.
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.
May I suggest an actual scientific discussion instead?
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.
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.
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”
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)?
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.
Eric steig
2017/03/20
Jim hunt: your question being whether we “saw this coming”?
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)
“… there are factions within the scientific community that work within the normal frameworks to provide contrarian views to reduce the mitigation imperative.”
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.
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.
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.
...
I think it was appropriate to publish as long as it passed peer review. It is dangerous to politicize research.
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.
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.
...Hi crandles,
Even if it is wrong, the scientific way to find out is publish and be damned. (or not damned)
...
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 crandles,
Even if it is wrong, the scientific way to find out is publish and be damned. (or not damned)
...
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.Hi jdallen,
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.
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...
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,
"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:
"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:
See Tamino's Analysis (https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/) from October 2015. -snip-
I don't see a slowdown. I'm looking forward to Tamino's next look into the matter.
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.
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.
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
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.
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.
Re: energy to melt arctic iceProbably 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.
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
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.(emphasis mine)
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.
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.
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.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.
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.
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.
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.
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.
we estimate that about
~42% (70% × 60%) of the sea-ice decline observed since 1979 in
September is due to internal variability.
So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss?
...
You are misrepresenting the Ding et al. paper. They never claimed that the disappearance of sea ice is mostly due to natural variability.
...
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.
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)
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:Quotewe estimate that about
~42% (70% × 60%) of the sea-ice decline observed since 1979 in
September is due to internal variability.
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 .
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.
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.
So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss?
So when can we expect this natural variability to flip back again and see a reduction in the rate of Arctic sea ice loss?
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!)
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.
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 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.
...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".
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).
...
The above criticism is nonsense.
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.
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.
...
Zero evidence for,"... they *want* to show...."
Zero evidence for, "using the specific model that best supports the conclusion they want to reach..."
...
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.
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)
The whole forum? Or just one (or a couple) out of 1200+ members?
Please remember:--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
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!
...
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:QuoteIn 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:QuoteHow 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)
...
Go tell these scientists they rigged the results to get the conclusion they wanted.
...
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.
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 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.
Don't worry, Archimid will pat you on the back.
You *don't* know who these authors are, do you? LOL.
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.
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"?
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.
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.
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.
...
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.
**Archimid pats AndrewB's 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.
...
"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."
Dunning - Kruger. If you believe that an expert opinion in a field is the same as a random blog comment, then you are insane.
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'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.
...
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.
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 :)
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 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.
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.
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)
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.
How do you mention a paper that hasn't even been published yet?APA REFERENCE STYLE: Unpublished Sources
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.
(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).
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.
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.
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.
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.
Back to content.
...
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.
...
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“
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/)QuoteAll 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“
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? ;)
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? ;)
It would be an excellent topic if he had real experts instead of three bozos and an expert....
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
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.
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.
But I don't expect any of them to bother answering your email
Friends, Romans, countrymen, lend me your ears;
Lamar Smith comes to bury Michael Mann, not to praise him
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
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)
For example, no, PV = nRT does not tell you how geopotential height responds to surface temperature!
An honest assessment of the literature (see IPCC for example) would say that the jury remains out on that.
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.
To the extent that the decadal tropical changes ARE a forced response, then our estimate for the natural variability is an upper bound,
Thanks for that post ktonine.QuoteFor 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.QuoteAn 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)QuoteTo 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.QuoteTo 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.
Or else...noise
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.
Or else...noise
There is no such thing as noise, only limits of the models.
OK. Here an update on the reply from the authors of Ding et al 2017.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):
Qinghua has indicated that he is not interested in an "ongoing blog-based discussion, which can quickly turn into a huge time sink".
...
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.
OK. Here an update on the reply from the authors of Ding et al 2017.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):
Qinghua has indicated that he is not interested in an "ongoing blog-based discussion, which can quickly turn into a huge time sink".
...QuoteQinghua 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.
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"."(emphasis mine)
Which is exactly the assumption that many here have expressed serious doubts about.
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.
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.
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.
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?
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".QuoteEric, 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.
I could not find it at a glance outside of the paid Nature publication however.
Thank you, jai mitchell.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)
"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)
angryIf 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.
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al. It just shows unprecedented warmth.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?
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.”
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.
...
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?
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?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.
Recent total warming is more than the Barnes ice sheet has seen before, and is sufficient to destabilise it.
...I don't want to defend Ding et al. But I do want to defend Peter.
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.
...
2X 'obviously' exceeded some tipping point with relation to the Barnes Ice Sheet.
...
Can anyone think of a physical mechanism that can account for 60% of the sea ice loss experienced from 1979 to 2014?
...
...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.)
The concept of "tipping point" does not apply to the Barnes ice cap.
...
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.”
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.
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. 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.
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
...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.)
The concept of "tipping point" does not apply to the Barnes ice cap.
...
...
'...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.
'...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.
...
You cannot prove they are wrong.
...
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?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.
We cannot have it both ways...
"... 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."
...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.
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.
...
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]
...
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.
...(emphasis mine)
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)
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.
...
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
Steig had a very nasty experience many years ago when Iago McIntyre came after him
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).
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.
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.)
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 ?
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.
That seems nearly too well timed to have been random chance. ;D
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.
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
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.
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.
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...
...Hi Archimid,
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.
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.
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...
Hi Archimid,
Sorry, but I don't think they proved that at all, and not even their conclusion states that.
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.
...
they conflate natural variability with anthropogenicaly altered random variability.
...
Quote from: AndrewBDragging 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.
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)
AndrewB
I'd quite like to know what Archimid meant by "anthropogenicaly altered random variability".
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"
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 ?
...
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!
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!
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...
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.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.
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.
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.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):
(...)
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.
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.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".
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!
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.
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?
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 still do not see how you can purport to distinguish signal from noise using models with no proven skill.
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?
I still do not see how you can purport to distinguish signal from noise using models with no proven skill.
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 e fficiently."
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.
Many thanks for all your interesting/burning/critical/constructive comments and questions on our paper and my thoughts.
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.link (http://www.spiegel.de/international/world/fast-forward-warming-point-of-no-return-for-the-arctic-climate-a-594461.html)
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.
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.
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.
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.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.
"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".
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.
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).
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 finda reasonan 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 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 circulationQuoteResults 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.
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.
... using tools that justify priori conclusions... sound like some of the worst insults you can throw to a scientist...
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!
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.
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.
AndrewBQuoteAnd 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?
...
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.
jaiQuoteearly 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.
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.
...was, actually. ECHAM6 is the new atmospheric circulation module of the Max Planck Institute for Meteorology's MPI-ESM model.
Then they used ECHAM5 which is the amtosphere modul of MPI-ESM-MR to examine atmospheric circulation.
...
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.
...Thanks for the link to the PDF.
Here is a link to the actual paper:
http://sci-hub.bz/10.1126/science.aag2345 (http://sci-hub.bz/10.1126/science.aag2345)
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)
Published online:27 March 2017
Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather EventsQuotePersistent 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)
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.
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 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...
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.
...A climate model is a mathematical tool, you can't blame the tool for any deficiencies in a climate science paper.
So maybe the model Ding et al use is not yet fit enough for the job (assuming the observations are basically correct)?
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.
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.
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.
Needless to say that there is much to argue about this paper's findings.
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.
In their study they make the following simplification:
CO2 forcing = AGW
Everything Else = Natural variation.
Abstracthttps://link.springer.com/article/10.1007/s00376-015-5028-4
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.
@ 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
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.
6. We need to stop allowing our scientific body to...Didn't the last POTUS tweet start along similar phrasing?
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?
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."
Global Warming will kill your children
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.
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
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.
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 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.
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 ...
...(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.
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 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.
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.
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)
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.
But misfit relative to CMIP5 mean doesn't imply internal variability!
CMIP5 mean likely does NOT capture true forced trend.
Archimid,
"1. The sea ice is melting out 40 years ahead of the models"
. . .
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
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 !
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'.
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.
A quick commentary on the commentary by Neil Swart.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):Quote from: Neil SwartThe 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.
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.
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.
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.
There are many possible reasons why the model mean could fail to explain the observed Arctic sea ice decline. For example:A quick commentary on the commentary by Neil Swart.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?Quote from: Neil SwartThe 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.
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.
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.
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.
-- 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). --
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.
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.
Thanks Michael, good summary of my thinking in better terms than I could articulate.
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.
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.
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.
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.
...(emphasis mine)
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)
We are dealing with a badly designed research paradigm. One that provides no useful information and makes claims not supported but merely conjectured.
I couldn't agree more.
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?
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?
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.
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?
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
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?
... if we want to have a good understanding while monitoring the comeback of Arctic sea ice. ...:o
... 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.
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?
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.
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,
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.
Bunkers are attractive but in the long run ineffective.... 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.Quotewhy 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.
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?
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?
... 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.Quotewhy 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.
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.
No, ktonine.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?
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".
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?
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).
...
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.
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."
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 ?
I was just reading this:
https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-scienceQuoteDing 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?
AndrewB,
Wow, curve fitting at best, why not using physical stuff, ah would change mind a little bit.
AndrewB,
Wow, curve fitting at best, why not using physical stuff, ah would change mind a little bit.
I was just reading this:
https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-scienceQuoteDing 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?
Eh...hmmm... what "physical" "stuff"?????
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.
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
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.
Dr Ding's most interesting answer is food for thought, and I'll probably spend a few many hours this weekend thinking about it.
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...
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 mindOren,
...
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.
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."
#421 on: Today at 11:11:11 PM »
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."
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.
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).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.
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).
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
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"
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)
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 ?
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.
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.
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.
Thanks for all your follow-up questions to my yesterday's threads . I will try to answer some of them.
I would suggest that Ding et al publish a public apology for their careless research which, frankly, makes no sense to my eyes.
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.
This thread is deadI 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.
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)
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.
Hi Rob,
Please see this plot. The sea ice extent in 1938/sep is even larger than that in 1938/aug.
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.
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).
In my opinion this is overconfidence in models, on global scale i would agree but in arctic i would be carefully (...)
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)?
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.
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.
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?
......
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"
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.
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]
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.
From wikipedia:QuoteAs 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)QuoteAtmospheric 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.
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.
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.
Might be getting OT :)
We are driving the climate, except we are driving blind.
it is still a good indication,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.
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)
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.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.
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.
and then to press on the tear glands is typical female behavior, first yell then cry.
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?
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.
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)
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.
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.
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.
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.
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 multidecadalhttp://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)
variability.
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.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.
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 :QuoteHowever, 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 ?
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.
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.
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 :
Jai, your second paper (Bellomo et al 2016) seems to deal mostly with cloud effects over the tropics:QuoteFrom 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 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.
For the sstClimAerosol simulation, the cloud albedo effect contributes significantly to the changes in land surface temperature and precipitation pattern (Fig S6).
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].
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.
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)
(note: never mind, I see that you do not have a science education background)
(note: never mind, I see that you do not have a science education background)
Please tell us the regression statistics.
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).
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?
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.
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 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.
Quote from: Rob Dekker on 4/18Also, 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 :
https://en.wikipedia.org/wiki/Kondratiev_wavefor 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.
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.
we conclude that models need external forcing to explain the magnitude, timing, and apparent multidecadal frequency of the observed twentieth century AMO variability.
It would be very difficult to expect an aerosol forcing component in the historical trend based on agricultural cycles.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).
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)Quotewe conclude that models need external forcing to explain the magnitude, timing, and apparent multidecadal frequency of the observed twentieth century AMO variability.
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."
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
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 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:
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.
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.
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.
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.
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.
Thanks for the answers. They bring clarity and more questions.
This is what the paper says about the fingerprint:QuoteInternal 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 believe that concentrating on minimum (just one day in the year) is not good enough.QuoteThe 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'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?
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?
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 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.
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. 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.
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.
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 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.
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. 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.