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AndrewB

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #150 on: March 25, 2017, 08:47:01 AM »
Back to content.

Yes, thank you Rob.

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

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

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

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

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

And had this been their conclusion in the published version of their paper, you and I and the rest of the world probably wouldn't even have taken notice of it. Well, I for one wouldn't, for sure.
« Last Edit: March 26, 2017, 08:08:38 AM by AndrewB »

DrTskoul

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #151 on: March 25, 2017, 11:47:10 AM »
Conclusions:
* expertise is earned. Because your name goes on a journal paper you are not automatically expert
* experts have blind spots and biases and make mistakes too
* because you just write in a forum of mostly amateurs you are not automatically an ignoramus
* if you want to criticise experts have your ducks in a row  ( thanks Rob)
* chill...

Jim Hunt

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #152 on: March 25, 2017, 11:58:39 AM »
At the risk of drifting off topic, may I take this opportunity to point out that whilst we debate how many angels can dance on the head of a pin the cryodenialospheric porky pie production line is cranking up to full speed once again?

Lamar Smith’s Show Trial for Climate Models

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

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

We also feel sure they were pleased to view the contents of another recent “white paper” published under the GWPF banner. The author was ex Professor Judith Curry, and the title was “Climate Models for the Layman“
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

DrTskoul

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #153 on: March 25, 2017, 12:22:25 PM »
At the risk of drifting off topic, may I take this opportunity to point out that whilst we debate how many angels can dance on the head of a pin the cryodenialospheric porky pie production line is cranking up to full speed once again?

Lamar Smith’s Show Trial for Climate Models

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

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

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

It would be an excellent topic if he had real experts instead of three bozos and an expert....

AndrewB

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #154 on: March 25, 2017, 01:08:30 PM »
At the risk of drifting off topic, may I take this opportunity to point out that whilst we debate how many angels can dance on the head of a pin...
And I always thought that here on ASIF we were debating how many angels can dance on the remaining Arctic sea ice in September?  ;)

DrTskoul

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #155 on: March 25, 2017, 01:27:59 PM »
At the risk of drifting off topic, may I take this opportunity to point out that whilst we debate how many angels can dance on the head of a pin...
And I always thought that here on ASIF we were debating how many angels can dance on the remaining Arctic sea ice in September?  ;)

Pinhead size guaranteed...

Jim Hunt

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #156 on: March 25, 2017, 06:11:21 PM »
It would be an excellent topic if he had real experts instead of three bozos and an expert....

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

Smith comes to bury Mann, not to praise him.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #157 on: March 25, 2017, 11:04:44 PM »
William Connolley replied to my criticism of Ding et al 2017 :

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

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

You’d expect the referees to pick this up -W
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Michael Hauber

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #158 on: March 25, 2017, 11:24:21 PM »
I've had the impression that since 2012 we've moved away from the dipole pattern which is so destructive for the ice, and the pattern discussed in this paper is kind of similar to the dipole.  To investigate further I've had a look at the Z200 height anomalies for every JJA year since 1996 over the Arctic, as analyzed in this paper.  I ignored years before 1995 as any appearance of the pattern before that time would reduce the trend.

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

I was a little surprised that there is no noticeable evidence that the pattern ended in 2012.  There was an almost opposite pattern present in 2013, and also 2016, but the pattern was there in 2014, and quite strong in 2015.  The other year with an opposite pattern was 2006, and the other strong years were 2005, 2007 and 2011.
Climate change:  Prepare for the worst, hope for the best, expect the middle.

Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #159 on: March 26, 2017, 07:50:39 AM »
I have emailed the authors Qinghua Ding, Eric Steig and Axel Schweiger for an opinion on my criticism of their paper.
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Neven

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #160 on: March 26, 2017, 08:50:34 AM »
Well done, Rob. Keep us posted, if you can.
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AndrewB

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #161 on: March 26, 2017, 08:58:33 AM »
I have emailed the authors Qinghua Ding, Eric Steig and Axel Schweiger for an opinion on my criticism of their paper.
I think that was the Right Thing To Do (tm) in this case, Rob.
But I don't expect any of them to bother answering your email, or much less discussing your criticism of their paper on a public forum, for three reasons:
  • You are not one of their peers, i.o.w. you are not a climate scientist.
  • A total of eleven co-authors signed on to this paper, and then it was peer-reviewed. As William Connolley indicated in his blog, you would expect the peer reviewers or at least one of the co-authors would have found such a mistake as the one you pointed to.
  • Last but not least: we are at a point in US history where climate scientists are fearing for their jobs and research budgets, facing a decidedly pro-fossil fuel industry administration which is expected to remain in place for at least the next eight years *. In this context, I would be surprised if any US climate scientist would concede any climate science paper as "bad science", specially if the criticism/rebuke comes from outside their closely-knit community, irrespective of the validity of such criticism/rebuke.

*: See the thread Trump Administration Assaults on Science here on ASIF
http://forum.arctic-sea-ice.net/index.php/topic,1858.0.html
« Last Edit: March 26, 2017, 10:06:23 AM by AndrewB »

Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #162 on: March 27, 2017, 02:49:22 AM »
Andrew, one of the "Four Agreements" (Google it) is : Don't make any assumptions.

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

Let me work out the logistics with them on how much and where they would like this discussion to be open to the public.
This is our planet. This is our time.
Let's not waste either.

AndrewB

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #163 on: March 27, 2017, 07:34:56 AM »
Andrew, one of the "Four Agreements" (Google it) is : Don't make any assumptions.

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

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

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

Note: I did Google "the Four Agreements". https://en.wikipedia.org/wiki/Don_Miguel_Ruiz
Very interesting!
« Last Edit: March 27, 2017, 07:48:36 AM by AndrewB »

Jim Hunt

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #164 on: March 27, 2017, 09:00:04 AM »
But I don't expect any of them to bother answering your email

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

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



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

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

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AndrewB

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #165 on: March 27, 2017, 10:11:02 AM »
Jim,
As usual your latest post on your blog is a must-read, and I just read it with particular interest, because it is in many ways related to this thread.
I am happy that my expectation that none of the co-authors of the Ding et al paper would answer Rob's email, proved wrong. But we are still missing the substance of Ding's technical reply.
In any case, I am grateful to Rob for his critical analysis effort and for reaching out to these scientists. That Ding himself answered is already proof that Rob was indeed onto something.

Neven

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #166 on: March 27, 2017, 02:40:55 PM »
Here's an example of why it is sometimes embarrassing when malicious motives are assigned to scientists when they publish papers that can be spun by climate risk deniers. From the Stoat discussion on the Ding et al. paper, where the #2 comment stated that 'Qinghua Din lead author, has signed off on other papers with Willie “oilcan” Song, collector of 1+ million dollars from oil, energy & business PR propaganda poopers':

Quote
Qinghua Ding
Goleta,CA
2017/03/26

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

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

Please check this if you want to know more

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

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

Anyway, I'm looking forward to a response to Rob Dekker's critique.
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ktonine

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #167 on: March 27, 2017, 11:14:07 PM »
While Rob D. hasn't been very forthcoming with the author's responses, Eric Steig has commented over at Stoat's:

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

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

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


Archimid

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #168 on: March 28, 2017, 03:23:23 AM »
Thanks for that post ktonine.

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

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

From Wikipedia:

 PV = nRT

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

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

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


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

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


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

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

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

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

I would love to see the lower bound. My bet it is on 0% bound for natural variability, but it could very well be 30-40% lower bound due to random variability extrinsic to the arctic. Random variability !=Natural variability.
I am an energy reservoir seemingly intent on lowering entropy for self preservation.

DrTskoul

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #169 on: March 28, 2017, 04:10:36 AM »
Thanks for that post ktonine.

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

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

From Wikipedia:

 PV = nRT

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

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

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


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

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


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

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

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

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

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

Sorry but dynamic variability = random variability = natural variability. The variability of the dynamic earth system. There is no unnatural random variability.

DrTskoul

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #170 on: March 28, 2017, 04:11:23 AM »
Or else...noise

Archimid

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #171 on: March 28, 2017, 04:48:59 AM »
Quote
Sorry but dynamic variability = random variability = natural variability. The variability of the dynamic earth system. There is no unnatural random variability.

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

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

There is also a man made component to the dynamic variability of the climate system.  It is also so complex that it seems random.
I am an energy reservoir seemingly intent on lowering entropy for self preservation.

Archimid

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #172 on: March 28, 2017, 04:51:30 AM »
Or else...noise

There is no such thing as noise, only limits of the models.
I am an energy reservoir seemingly intent on lowering entropy for self preservation.

oren

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #173 on: March 28, 2017, 05:44:13 AM »
We are now down to philosophy. In practical terms, the question is whether the circulation changes are "random" in that there is no underlying trend in them, even if influenced by human activities. In such a case, sea ice should rebound when the random dice roll the other way. OTOH, if the circulation changes have an underlying noisy trend due to human activities, then sea ice ain't coming back.
(My own worthless opinion is in the second camp)

Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #174 on: March 28, 2017, 07:00:43 AM »
OK. Here an update on the reply from the authors of Ding et al 2017.
Qinghua has indicated that he is not interested in an "ongoing blog-based discussion, which can quickly turn into a huge time sink".

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

There simply is no evidence of that.
« Last Edit: March 28, 2017, 07:06:00 AM by Rob Dekker »
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DrTskoul

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #175 on: March 28, 2017, 12:15:51 PM »
Or else...noise

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

I think we are talking past each other... The notion of randomness and noise is perfectly compatible with deterministic dynamical systems.  You can follow every motion of every molecule or describe an average behavior using the notions of random walk and noise.  Brownian motion is fully deterministic yet can be perfectly described as thermal noise. Turbulence is another example. White noise is a Gaussian distribution....  all these are convenient analytical tools.  Volcanoes which are a source of climate variability are perfectly deterministic but can also be described by a random or stochastic process.
« Last Edit: March 28, 2017, 12:23:31 PM by DrTskoul »

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #176 on: March 28, 2017, 12:28:31 PM »
OK. Here an update on the reply from the authors of Ding et al 2017.
Qinghua has indicated that he is not interested in an "ongoing blog-based discussion, which can quickly turn into a huge time sink".
...
The latest development is that, Qinghua Ding seems to have changed his position somewhat, because he posted the following in the Stoat blog (link below):
Quote
Qinghua Ding
Goleta,CA
2017/03/28

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

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

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.

DrTskoul

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #177 on: March 28, 2017, 12:36:31 PM »
OK. Here an update on the reply from the authors of Ding et al 2017.
Qinghua has indicated that he is not interested in an "ongoing blog-based discussion, which can quickly turn into a huge time sink".
...
The latest development is that, Qinghua Ding seems to have changed his position somewhat, because he posted the following in the Stoat blog (link below):
Quote
Qinghua Ding
Goleta,CA
2017/03/28

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

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

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

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

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

which brings us to the realisation that nobody is fully free of confirmation bias.

josh-j

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #178 on: March 28, 2017, 01:42:08 PM »
Eric's latest and probably last comment on the Stoat blog also confuses matters further, because first he dismisses Rob's critical analysis as "nonsense", but then he takes his time to repeat that "we assume, in effect, that most of the trend in Z200 is "natural variability"."

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

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

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

The 2014 paper is, I believe, the following:

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

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

I think if we have doubts about an assumption of natural variability in Z200 (I have no idea myself), it might worth looking at this paper, not just the 2017 one. I could not find it at a glance outside of the paid Nature publication however.

Jim Hunt

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #179 on: March 28, 2017, 01:48:06 PM »
Jim,

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

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

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Quote
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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #180 on: March 28, 2017, 03:41:38 PM »
The latest chapter and hopefully the final one.

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

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

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

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

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

There simply is no evidence of that.

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

Rob based his claim on the  idea that the regression factor removed all of the trend.  It did not.

jai mitchell

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #181 on: March 28, 2017, 04:13:12 PM »
I could not find it at a glance outside of the paid Nature publication however.

http://geog.ucsb.edu/~qinghua/pdf/24.pdf
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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #182 on: March 28, 2017, 07:46:23 PM »
I could not find it at a glance outside of the paid Nature publication however.

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

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

As far as I know, in climate science just as in other sciences, physical evidence is stronger proof than any conclusions derived from models. Which brings us back to the methodology used by Ding et al in both the 2014 and 2017 papers, the assumptions they make, the models they chose to use, and the conclusions they reach from their model simulations.

ktonine

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #183 on: March 28, 2017, 07:57:38 PM »

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

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

It's the sun! It's the wind! It's cosmic rays! It's clouds!  Sound familiar?  It's what we hear from deniers whenever you mention CO2.  You are sounding just like them - simply unable to admit you were wrong and continually searching for some *other* reason to deny it might actually be natural variability.
« Last Edit: March 28, 2017, 09:11:36 PM by Neven »

jai mitchell

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #184 on: March 28, 2017, 08:12:09 PM »
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.

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

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

see:

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

“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

“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.”
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Darvince

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #185 on: March 28, 2017, 08:26:50 PM »
angry
If a certain poster is bothering you so much, there is an ignore feature that allows you to hide people's posts. However, before the posts are hidden, you must check the "Hide messages posted by users on my ignore list" checkbox under Profile > Modify Profile > Look and Layout.

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #186 on: March 28, 2017, 11:39:41 PM »
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.

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

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

see:

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

“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

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

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

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

http://www.nature.com/nature/journal/v145/n3671/abs/145376a0.html

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #187 on: March 29, 2017, 01:44:14 AM »
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.
...
jai mitchell, did you check where the Barnes ice cap is located? It's on Baffin Island, just across from Greenland. See the attached image.

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

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

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

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

The paper by Gilbert et al about the Barnes ice cap supports the assertion that anthropogenic forcing is responsible for the unprecedented warming in the region, "unprecedented" being the key word here. It directly contradicts the claim in the Ding et al 2014 paper that (quoting from the abstract) "... a substantial portion of recent warming in the northeastern Canada and Greenland sector of the Arctic arises from unforced natural variability."
« Last Edit: March 29, 2017, 01:58:56 AM by AndrewB »

Peter Ellis

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #188 on: March 29, 2017, 11:48:54 AM »
If half the warming in the northeastern Canada and Greenland region is - as the Ding et al 2014 paper suggests - due to natural variability, how come this "natural variability" has not once affected the Barnes ice cap in the last 2,000 years?

Uh, this is trivial maths.

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

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

Fundamentally, the straw does not need to outweigh the camel in order to break its back.

AndrewB

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #189 on: March 29, 2017, 12:39:19 PM »
If half the warming in the northeastern Canada and Greenland region is - as the Ding et al 2014 paper suggests - due to natural variability, how come this "natural variability" has not once affected the Barnes ice cap in the last 2,000 years?

Uh, this is trivial maths.
...
Fallacious argument. You are assuming that the present warming due to natural climate variability is by far the largest in over 2,000 years, in other words you just played Russian roulette every summer in over 2000 years, survived unscathed for over 1960 years but died continuously the last 40 years. Not very likely, is it?
Warming (in the northeastern Canada and Greenland region) due to "natural climate variability" has peaked many times over the 2,000 years covered by physical evidence (the cosmogenic nuclides), and it was not enough to affect the Barnes ice cap.
But recent warming is definitely signaling the demise of the Barnes ice cap. Attribution of a large part of this unprecedented warming to anything else than AGW contradicts the very definition of "natural climate variability" as a random phenomenon and, is just bad science. And when this claim is based on model simulations, just an unwarranted use of models. Which is exactly the reason I and others have been questioning the fact that the models-based methodology of Ding et al does not support their conclusions.
« Last Edit: March 29, 2017, 06:59:05 PM by AndrewB »

Jim Hunt

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #190 on: March 29, 2017, 02:19:56 PM »
Fallacious argument.

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

In particular, "what if natural variability is exactly the same today as it has been for the last 10,000 years?"
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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #191 on: March 29, 2017, 04:20:34 PM »
Can anyone think of a physical  mechanism that can account for 60% of the sea ice loss experienced from 1979 to 2014?  Such mechanism should reflect the very small loss rate from 1979-2007 and an acceleration from 2007-today.

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

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

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

I am an energy reservoir seemingly intent on lowering entropy for self preservation.

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #192 on: March 29, 2017, 04:53:10 PM »
...
If the first X varied naturally for thousands of years without destabilizing the ice sheet and only when humans added the second X was the ice destabilized, the ice loss is 100% due to to human warming.
I don't want to defend Ding et al.  But I do want to defend Peter.

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

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

I, too, question (the unread by me) Ding et al.  There were driftwood studies and Arctic Ocean ice shelves that suggest what has happened to Arctic ice these past 30 years is seriously unprecedented these past several thousand years.  I'd hazard a guess of a factor of 10, rather than 2.
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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #193 on: March 29, 2017, 07:27:04 PM »
...
2X 'obviously' exceeded some tipping point with relation to the Barnes Ice Sheet.
...

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

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

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

https://en.wikipedia.org/wiki/Flying_Spaghetti_Monster
« Last Edit: March 29, 2017, 07:48:14 PM by AndrewB »

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #194 on: March 29, 2017, 07:45:29 PM »
Can anyone think of a physical  mechanism that can account for 60% of the sea ice loss experienced from 1979 to 2014?
...

Archimid, there is a single physical mechanism that melts ice, and it's energy (heat). And we know that the Arctic is warming 2.5~3 x faster than the rest of the world.
So the question is, how does heat from lower latitudes reach the Arctic? There are only two possible ways: either the oceans or the atmosphere. The relative percentages are irrelevant. We just know that this extra heat is due to the present energy imbalance of our planet as a whole (AGW).
In other words, whatever ocean currents or atmospheric circulation patterns you want to invoke to explain the demise of the Arctic sea ice, the heat/energy being transported to the Arctic is the result of an anthropogenic forcing, and certainly NOT "natural climate variability".
« Last Edit: March 30, 2017, 08:31:54 AM by AndrewB »

Archimid

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #195 on: March 29, 2017, 11:18:54 PM »
AndrewB, I agree with you but I was hoping that I was missing something that the "natural variability"  folks know.

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

Then you have the Arctic. Since 1979 it has been in decline yet the PDO has oscillated several times. It has been mostly positive for decades and mostly negative for decades. Yet through positives and negatives the arctic decline continues. At most, the natural variability of the PDO is responsible for the rate of melt. During negative cycles the arctic melts slowly and during a positive cycle it melts faster. But it melts either way. Thus 100% of the melt is anthropogenic, but the rate of melt has natural variation in it.
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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #196 on: March 29, 2017, 11:55:59 PM »
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The concept of "tipping point" does not apply to the Barnes ice cap.
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I say it does!  The ice cap wasn't melting faster than it was expanding for a very long time, and now it is.  (And what caused approximately 100% of this change, I'm sure, is AGW.)

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

As to figuring out what non-AGW variability is affecting Arctic sea ice, there is "weather" - functionally good-for-melting seasons vs. good-for-keeping-ice-around seasons.  The generic AGW conditions were similar, but the Arctic responses in 2007 and 2012 were very different from 2013 and 2014.  If an 'average' season is half-way between these two pairs, what metric would one use to derive percentages (low points, high points, area, volume, some combination???)?  My biggest problem with this approach is that weather patterns are changing because of AGW.
Arctic ice is healthy for children and other living things.

Michael Hauber

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #197 on: March 30, 2017, 12:56:40 AM »
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.

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

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

see:

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

“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

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

Your argument might work if Aerosol was 100% of NA variability, or if the proposed link between Arctic ice cover and variability being discussed in this thread was about the Atlantic instead of the Pacific.
Climate change:  Prepare for the worst, hope for the best, expect the middle.

ktonine

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #198 on: March 30, 2017, 01:11:49 AM »

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

see:

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

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


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

I'm also not sure when volcanoes became part of anthropogenic emissions.  Not all aerosols are anthro - just sayin'

Michael Hauber

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #199 on: March 30, 2017, 01:19:16 AM »

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

The PDO has only oscillated once.  Maybe the start of a second oscilation if it turns out that the warm PDO for the last few years is a real warm phase and not a false alarm.  A trend analysis 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.
Climate change:  Prepare for the worst, hope for the best, expect the middle.