An interesting new paper on Arctic sea ice has just been published. According to the conclusions of “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice“:

Although positive feedbacks between sea ice and the Arctic circulation exist, we find that these are small during summer. Instead, circulation variations over the Arctic have been a significant factor in driving sea-ice variability since 1979, and have had a non-trivial contribution to the total surface temperature trend over Greenland and northeastern Canada39 . The potentially large contribution of internal variability to sea-ice loss over the next 40 years reinforces the importance of natural contributions to sea-ice trends over the past several decades. The similarity of high-latitude circulation variability associated with sea-ice loss to the teleconnections with the tropical Pacific suggests a contribution of sea-ice losses from SST trends across the tropical Pacific Ocean. Decadal trends in the hemispheric circulation are an important driver of Arctic climate change, and therefore a significant source of uncertainty in projections of sea ice. Better understanding of these teleconnections and their representation in global models under increasing greenhouse gases may help increase predictability on seasonal to decadal timescales.

As you may already be able to imagine, this paper (PDF as submitted) is already the source of considerable controversy! Firstly let’s take a look at an overview of the paper from the University of Washington, entitled “Rapid decline of Arctic sea ice a combination of climate change and natural variability”:

“The idea that natural or internal variability has contributed substantially to the Arctic sea ice loss is not entirely new,” said second author Axel Schweiger, a University of Washington polar scientist who tracks Arctic sea ice. “This study provides the mechanism, and uses a new approach to illuminate the processes that are responsible for these changes.”

[First author Qinghua] Ding designed a new sea ice model experiment that combines forcing due to climate change with observed weather in recent decades. The model shows that a shift in wind patterns is responsible for about 60 percent of sea ice loss in the Arctic Ocean since 1979. Some of this shift is related to climate change, but the study finds that 30-50 percent of the observed sea ice loss since 1979 is due to natural variations in this large-scale atmospheric pattern.

Now let’s take a look at another overview of the paper, this time from Roz Pidcock at Carbon Brief and entitled “Humans causing up to two-thirds of Arctic summer sea ice loss, study confirms”:

Rising greenhouse gas emissions are responsible for at least half, possibly up to two-thirds, of the drop in summer sea ice in the Arctic since the late 1970s, according to new research. The remaining contribution is the result of natural fluctuations, say the authors.

The paper, published today in Nature Climate Change, confirms previous studies which show how random variations in the climate have acted to enhance ice loss caused by rising CO2.

Importantly, the authors state clearly in the paper that their work does not absolve human activity as a driver of Arctic sea ice loss. A News and Views article that accompanies the paper, by Dr Neil Swart from Environment and Climate Change Canada, adds:

“The results of Ding et al. do not call into question whether human-induced warming has led to Arctic sea-ice decline — a wide range of evidence shows that it has.”

There has already been much debate about the paper on Twitter! Here’s the “scientific” edition:

and here’s the “skeptical” edition:

Needless to say Anthony Watts swiftly stepped up to the plate on the “skeptical” side of the “debate” with a guest article on his blog by David Middleton entitled “Arctic ice loss driven by natural swings, not just mankind: study” which begins by quoting a similarly titled Reuters article by Alister Doyle:

Natural swings in the Arctic climate have caused up to half the precipitous losses of sea ice around the North Pole in recent decades, with the rest driven by man-made global warming, scientists said on Monday.

The study indicates that an ice-free Arctic Ocean, often feared to be just years away, in one of the starkest signs of man-made global warming, could be delayed if nature swings back to a cooler mode.

Natural variations in the Arctic climate “may be responsible for about 30–50 percent of the overall decline in September sea ice since 1979,” the U.S.-based team of scientists wrote in the journal Nature Climate Change.

David embellished his article with some “humorous” asides such as:

“This is the worst of the worst catastrophes in the world! Oh, it’s crashing … Oh, the humanity! Honest, I can hardly breathe. I’m going to step inside where I cannot see it.”

Please say it ain’t so!!!

“The melt of the Arctic is disrupting the livelihoods of indigenous peoples and damaging wildlife such as polar bears and seals while opening the region to more oil and gas and shipping.”

which some of us took exception to:

David – An Arctic indigenous person of my acquaintance asks me to tell you to “go f(r)@ck yourself”!

What should I reply on your behalf?

No answer has yet been received to that (im)pertinent question!

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

[Edit – March 18th]

I tried this Google search this morning:

38,000 results. We’re number 4. If you repeat the exercise please feel free to experiment with the search phrase(s) you employ. Make sure to only click on the link that leads you back here!

Watch this space.

Alternative Points of View – Scientific

William M. Connolley (AKA Stoat)

Without being able to pick any obvious holes I feel somewhat uncomfortable with that; the idea that September ice depends just on JJA circulation doesn’t feel at all right. Having decided that, though, they then run a variety of model experiments, for example “nudging” the circulation back to re-analysis, with and without an ocean-ice model underneath. And the result seems to be that it is mostly the circulation forcing the sea ice, rather than the sea ice changes forcing the atmosphere. This kinda-fits the “information flow” meme from way back so I should be prepared to accept that mostly. Having done that they then convince themselves that most of the circulation changes that matter to the ice are not GW forced, and so must be natural variability; and hence the conclusion. If you took all of this at face value then they’d have solved one of the puzzles, that on the whole models show much less ice decline that reality. But of course if the decline is substantially a freak of variation, not forced, that would fit.

The flaw in this overall, without looking at the details, is that it’s hard to see a near-40-year trend and being so much natural variability. That seems to be asking for an awful lot of one-way variation.

The Science Media Centre

Prof. Andrew Shepherd, Director of the Centre for Polar Observation and Modelling at the University of Leeds, said:

“According to this new research, the dramatic decline in Arctic sea ice that we have witnessed over recent decades is primarily due to anthropogenic (man-made) climate warming.

“Although this finding may not come as a surprise, being able to separate this from the effects of natural climate variability is an important step forwards, and paves the way for an improved understanding of what we should expect in future decades.”

Dr Ed Hawkins, Climate research scientist at the University of Reading, said:

“Recent summer Arctic sea ice extents have all been amongst the lowest on record but this is not necessarily all due to warming global temperatures – part of the sea ice decline is also because of changes in the atmospheric circulation.

“It is challenging to determine how much of the change in the circulation is itself due to warming temperatures, but this study suggests that a substantial fraction is due to natural fluctuations.

“Looking ahead, it is still a matter of when, rather than if, the Arctic will become ice-free in summer, but we expect to see periods where the ice melts rapidly and other times where it retreats less fast.”

Archived Alternative Points of View – “Skeptical”

Colin Fernandez at the Daily Mail

HALF of Arctic ice loss is driven by natural swings and not global warming, controversial study claims

• Decline in ice cover due to ‘random’ and ‘chaotic’ natural changes in air currents
• The rest has been driven by man-made global warming, scientists said

Colin Fernandez’ Daily Mail article reproduced at the “Global Warming Policy Forum”

The Arctic icecap is shrinking – but it’s not all our fault, a major study of the polar region has found. At least half of the disappearance is down to natural processes, and not the fault of man made warming.

Part of the decline in ice cover is due to ‘random’ and ‘chaotic’ natural changes in air currents, researchers said.

The rest has been driven by man-made global warming, scientists said.

The research means that although it is widely feared that the Arctic could soon be free of ice, this could be delayed if nature swings back to a cooler cycle.

Colin Fernandez’ Daily Mail article reproduced at Mark Morano’s “Climate Depot”

Study in journal Nature: HALF of Arctic ice loss driven by natural swings — not ‘global warming’

David Middleton at Anthony Watts’ “Watts Up With That”

From the No Schist, Sherlock files…

Perspective: NSIDC Arctic Sea Ice Index Interactive Graph

The five earliest years of data plot near +2 standard deviations. The five most recent full years of data plot near or just outside of -2 standard deviations. Ding et al., 2017 conclude that up to half of the difference is due to the NAO and other natural climate fluctuations.

Paul Homewood at “Not a Lot of People Know That”

Shock news! Scientists discover natural climate cycles.

Astonishingly though, the study makes no mention of the Atlantic Multidecadal Oscillation, which also has a significant effect on Arctic sea ice extent.

Since the late 1970s, the AMO has moved from the coldest point of its cycle to its highest, coinciding with a decline in Arctic sea ice coverage.

Patrick Michaels and Paul “Chip” Knappenburger at “The Cato Institute“:

Considering that the climate models are already performing poorly as it is, the new finding means that they are actually faring even worse than has been generally realized. And accounting for this strengthens the case for a lukewarming future from greenhouse gas emissions.

Ring up another strike against the climate models, and another reason why basing government policy on their output is a bad idea.