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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,1858.0.html

Developers Corner / Re: The Distributed Arctic Sea Ice Model
« on: March 25, 2017, 02:12:24 PM »
I am aware I am kind of resurrecting this thread, but just wanted to note two things:
  • A crowd-funded, collaboratively developed, Open Source climate model is always a Good Idea (tm) imho.
  • The significant caveat here, according to my limited expertise in the subject, is that parallel climate simulation algorithms require high bandwidth and low latency interconnects between computing nodes. Hence most are run in batch mode on supercomputers, and do not lend themselves to a distributed environment.

Note that some (many?) climate models are Open Source and their source code is freely available for academic purposes. But honestly, downloading this kind of source code which would take months to run on a desktop PC doesn't seem very practical to me.
So I guess we'll always have to keep counting on large, expensive supercomputer resources for running the latest, most sophisticated climate simulations, including sea ice models.

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?  ;)

Back to content.

Yes, thank you Rob.

: 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.

The Polar Prediction Workshop 2017 (PPW 2017) and the 2nd Sea Ice Model Intercomparison Project Meeting (2nd SIMIP Meeting) will be held at Deutsches Schiffahrtsmuseum ( in Bremerhaven, Germany from 27th to 30th March 2017. Both events are jointly organized by the Polar Climate Predictability Initiative (WCRP-PCPI), the Polar Prediction Project (WWRP-PPP), the Sea Ice Prediction Network (SIPN), and the Sea Ice Model Intercomparison Project (SIMIP).

The list of papers presented for discussion can be found here:

Among others, I just wanted to single out the paper by Dirk Notz, titled:
"When is all the sea ice gone?"

A literally burning question these times...

How do you mention a paper that hasn't even been published yet?

APA REFERENCE STYLE: Unpublished Sources
: Neven
AndrewB, you've made your point. Now don't reiterate it constantly by nitpicking details. Thanks.

You are welcome, Neven. Keep up the good work.

Somehow, the Ding et al paper "forgot" to even mention it...

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

Steven, the Notz paper was submitted on 29 March 2016, four months before the Ding et al paper was submitted. With 11 co-authors, you would expect at least one among Ding et al. would have been aware of the Notz et al paper about the Sea-Ice Model Intercomparison Project (SIMIP), or at least about the SIMIP project itself, which exists since late 2015/early 2016 as far as I can tell. The climate model community is not that large.
Also, check where Notz works and where Ding et al got the ECHAM5 model from.

However, arctic is probably the most difficult place on earth to model because of ice and snow, the large temperature differences and the complex geography.

I agree. The Arctic is particularly difficult to model, as you say because of ice, snow, the ocean, the temperature range, the geography, the huge scale and numerous feedbacks and how all these interact. It's a complex system with a lot of chaos.
You might be interested in checking this paper:
The CMIP6 Sea-Ice Model Intercomparison Project (SIMIP): understanding sea ice through climate-model simulations
by Dirk Notz, Alexandra Jahn, Marika Holland, Elizabeth Hunke, François Massonnet, Julienne Stroeve, Bruno Tremblay and Martin Vancoppenolle

Somehow, the Ding et al paper "forgot" to even mention it...

So the question really is, are models right or wrong (or perhaps something in between), and I don't think this paper provides much help in answering that.

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

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

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

Two videos with Gavin Schmidt about the use of models in climate science: (TED talk) (1 hour lecture, with very bad sound unfortunately)


**Archimid pats AndrewB's back**

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


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

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

The 30~50% attribution is found in the abstract:
"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."

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

Neven, I am not quite sure what to make of what you just wrote here, so please help me out here.
  • Are we ignoramuses just supposed to shut up unless we agree with every word in the Ding et al paper?
  • Should we kowtow every time the name of one of the eleven co-authors is mentioned?
  • Or should we just go about our own lives, because the Ding et al paper is just an insignificant bit of bad science, not worth spending our precious internet time on?
(I hope a little bit of humor is allowed in this thread, to lighten up the atmospheric circulation mood)

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

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

You are suggesting that they didn't, in other words you are suggesting that they randomly chose some climate models, ran their simulations, and then were collectively surprised to find out that "atmospheric circulation" in the months of June-July-August shows a high correlation with Arctic sea ice extent in September, in their simulation runs.

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:

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

And further down:

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)

They are using an *atmospheric circulation model* to assess atmospheric circulation and only tying it to an ocean module when they want to see the near surface effects on SSTs (top 50 meters).
Of course they are using an (obsoleted version of an) atmospheric circulation model (ECHAM5). Because they want to show that the decline in Arctic sea ice in September is mostly due to atmospheric circulation variability in the Arctic in June-July-August, which they then attribute to "natural climate variability".

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

Why don't they use the specific Arctic sea ice model from the Max Planck Institute for Meteorology? Why don't they quantify the skill of the models they use, and compare them to other models for Arctic sea ice?

Thank you Rob for your brilliant dissection of the Ding et al paper. We are still waiting for any of the authors to manifest themselves and respond to your sharp criticism or any of the other questions raised by their scientifically questionable and evidence-defying "natural climate variability" attribution for Arctic sea ice decline, here on ASIF or on the Stoat blog comments section.

Meanwhile, 2017 just saw the lowest maximum Arctic sea ice extent on record, 2016 was the third hottest year on record in a row and 1.1C above pre-industrial, and atmospheric CO2 concentration has passed the 405ppm threshold, 125ppm above pre-industrial and probably the highest it has been in over 1 million years. And 25% of the world's corals died last year.

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

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

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

From the conclusion in the final submitted version:

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

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

Back on-topic to the discussion of the Ding et al paper, I would like to point to an excellent rebuke of the Ding paper on a scientific basis, written by Rob Dekker in a long comment on the Stoat blog, which you all can find here:
Here is Rob's conclusion, with which I agree 100%:
That would have been a fine conclusion, but is completely different from their conclusion that “summertime atmospheric circulation” may have contributed as much as 60% to the September sea-ice extent decline since 1979.
It’s not “summertime atmospheric circulation” that caused it; it is “summertime climate change (with ALL the variables, including temperature) being the cause. And with AGW being real, we know that temperature for one is NOT a natural variability variable.

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

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

(emphasis mine)

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

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

Also, if I may add, it is a well-known fact here at ASIF, that the weather (natural variability) during the months of June-July-August is a determining factor in how low September ice extent will go. But that in no way is the correct attribution for the year-round exponential decrease TREND in Arctic sea ice volume, which we can observe since the beginning of satellite records, as evidenced by this excellent chart:

AndrewB, welcome and thank you for putting it so concisely. To me argument 1 is still the most important, and I find the scientific claim highly questionable. The negative arctic sea ice trend is so obvious that attributing it to variable natural causes unrelated to AGW and GHGs using a model, probably means the model is not good enough.

Hi oren,
Thank you for your comment. Indeed the Ding et al paper makes the following claim, found in the abstract:
"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:
1) ECHAM5, an atmospheric general circulation model developed at the Max Planck Institute for Meteorology (see Actually ECHAM5 is not intended for modeling Arctic sea ice, and has been superseded by ECHAM6. Why Ding et al chose to use an obsolete version of an atmospheric general circulation model beats me - unless they wanted a model that would best fit their foregone conclusions. The source code for ECHAM6 is freely available for lawful scientific use, and you can basically run the model on a properly configured desktop Linux workstation.
Now, even more puzzling is that the Max Planck Institute for Meteorology actually has a model specifically developed for modeling Arctic sea ice, see here ( and here (
2) A global coupled ocean/sea-ice (POP2-CICE4) model, developed at UCAR (Ding). See for details. Obviously Ding is most familiar with POP2-CICE4.

The paper is lacking in that they don't quantify the skill of the models they used, they just claim they are "better" (actually they don't even use the word "skill", which is the proper technical term). I would suggest they used the models that "better" worked out to show their claim that sea ice decline is mostly the result of "natural climate variability". A clear example of manipulating your "experiment" to reach a desired conclusion.

Actually, I don't think they asserted most of the loss was from natural variation, and I suggest the philosophical discussion get moved to an appropriate thread.
Hi jdallen,
From the abstract of the paper:
Our experiments indicate that the circulation trend may have contributed as much as 60% to
the decline of the September sea ice extent minimum since 1979.

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

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

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

"Climate scientists can't even agree among themselves whether climate change (or how much of it) is the result of human activity."
"It's not settled science."
"CO2 is not the main driver of climate change."
"They were growing wheat in Greenland some centuries ago and nobody was any worse for it."

Even if it is wrong, the scientific way to find out is publish and be damned. (or not damned)
Hi crandles,
Again, I am not even arguing about the scientific value of the Ding paper per se here, or how it was worded, or how many caveats it was filled with.

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

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

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

Now, of course since they have already been published, they have legitimized the clearly false assertion that the year-round disappearance of Arctic sea ice which will occur over the coming few decades is mostly due to "natural climate variability". You could demonstrate that they are entirely wrong, de-construct all the fallacies in their tortuous reasoning, dissect their various logic mistakes, point to each and every dubious assumption they make in the paper, it wouldn't matter: they cannot be unpublished. And clearly, people with such an oversized ego are not going to retract themselves or even admit that they were wrong and wrote a piss-poor excuse of a climate science paper.
So there you have it.
Arctic sea ice is going to disappear over the coming years but now the takeaway from this man-made disaster is that it's mostly "natural climate variability". Crappy (un)science is the new normal.
Talk about improving communications between climate scientists and the general public!


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.

First, thank you Neven for practically immediately releasing my profile and welcoming me into the ASIF community. Also, thank you Archimid for starting this thread, and thank you Andre, Jim Hunt, jai mitchell, Jim Williams and oren, for your replies/comments.

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

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

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

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

Michael E. Mann has previously calculated that if we wanted to keep global warming under 2C, we would have to keep CO2 concentration under 450ppm; that was allowing for a 0.5C overshoot for a few decades, AND the widespread use of negative emission technologies after 2050. Without the widespread use of negative emission technologies after 2050, we would have to keep CO2 concentration under 405ppm. (see

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

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

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

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

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

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

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

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

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

Just a few charts to support my opinions above, mainly that the disappearance of sea ice is NOT due to any kind of "natural climate variability", despite what Ding's "improved" models may show or not:

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