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Tuesday, January 12, 2010

Joseph Romm: Met Office’s Richard Betts incorrectly asserts “the dramatic decline in Arctic sea ice in 2007 … was then partly reversed in 2008 and 2009”

Met Office’s Richard Betts incorrectly asserts “the dramatic decline in Arctic sea ice in 2007 … was then partly reversed in 2008 and 2009.”

by Joseph Romm, Climate Progress, January 12, 2010

Memo to media, non-cryosphere scientists:  The peer-reviewed literature does not provide support for the view that the Arctic “recovered” in 2008 — and even what happened in 2009 has now been called into question (see below).   Don’t fall into the mindset of the anti-science disinformers, who all seem to think two dimensionally.

In July 2009, leading cryoscientists at JPL, the Polar Science Center at the University of Washington, and NASA published a major peer-reviewed article, “Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008” (discussed here) and posted this figure of Arctic ice volume:

Not bloody much “recovery” or “reversal” from 2007 to 2008.
Now Andy Revkin has just posted a typical Goldilocks piece on Dot Earth — it’s not too hot, it’s not too cold.  I don’t want to rehash all of my problems with this approach, but I will say that since the observational evidence shows that warming of the climate system is “unequivocal” — and essentially the entire scientific community and every member government of the IPCC agrees with that analysis — it is clearly reasonable for the media to discuss certain very unique, extreme weather events predicted by climate science in the context of that warming — as Revkin himself once did in discussing the remarkable extremes in Australia last year [see CNN, ABC, WashPost, AP, blow Australian wildfire, drought, heatwave “Hell (and High Water) on Earth” story — never mention climate change].  Since we’re not in a cooling trend, of course, it would be illogical for a competent reporter to use a cold snap as evidence of such a non-existent trend.

I want to focus on a quote he got from Richard Betts, the head of the climate impacts division at Britain’s Met Office, which shows that even the most knowledgeable climate experts don’t follow the literature as closely as they should:

One classic example is the dramatic decline in Arctic sea ice in 2007, which was then partly reversed in 2008 and 2009. Although there is still definitely a declining trend in Arctic sea ice (2009 and 2008 were still the second and third lowest sea ice extents, after 2007) there was a lot of hype surrounding the 2007 minimum even though that was partly just natural variability in the Arctic climate.
Well, we’ve already seen that Betts was wrong abut the reversal in 2008.  He was focused on the two-dimensional Arctic ice coverage, and apparently missed the sharp drop in volume, which I dare say is “dramatic” and much more important.

The scientific literature has also weighed in on the cause of the 2007 decline (see “What drove the dramatic retreat of arctic sea ice during summer 2007?“). Let me quote from the Geophysical Research Letters (subs. req’d) analysis by four scientists from the Polar Science Center, Applied Physics Laboratory, College of Ocean and Fishery Sciences, University of Washington, Seattle:
A model study has been conducted of the unprecedented retreat of arctic sea ice in the summer of 2007. It is found that preconditioning, anomalous winds, and ice-albedo feedback are mainly responsible for the retreat. Arctic sea ice in 2007 was preconditioned to radical changes after years of shrinking and thinning in a warm climate.The Arctic Ocean lost additional (sic) 10% of its total ice mass in which 70% is due directly to the amplified melting and 30% to the unusual ice advection, causing the unprecedented ice retreat. Arctic sea ice has entered a state of being particularly vulnerable to anomalous atmospheric forcing.
So, yes, that minimum was partly due to natural variability, but in fact it was mostly due to warming. 
Arguably, absent the warming trend, there’d have been exceedingly little chance of anything like the 2007 decline.

Final question:  Did the ice recover from 2008 to 2009?  To answer, that you must read the new study, “Perennial pack ice in the southern Beaufort Sea was not as it appeared in the summer of 2009” (subs. req’d), which I discussed at length here:  “Where on Earth is it unusually warm? Greenland and the Arctic Ocean, which is full of rotten ice.”

That study concluded:
Our results are consistent with ice age estimates (Fowler & Maslanik, that show the amount of MY sea ice in the northern hemisphere was the lowest on record in 2009 suggesting that MY sea ice continues to diminish rapidly in the Canada Basin even though 2009 areal extent increased over that of 2007 and 2008.
If it’s true that the amount of multiyear sea ice in the northern hemisphere was the lowest on record in 2009, then it is hard to say that there was any genuine recovery.

Second, the satellite and other measurements that suggested two-dimensional recovery of sea ice extent have been called into question.  It appears an unfortunate trick of Nature helped hide the decline of Arctic ice:
In September 2009 we observed a much different sea icescape in the Southern Beaufort Sea than anticipated, based on remotely sensed products. Radarsat derived ice charts predicted 7 to 9 tenths multi-year (MY) or thick first-year (FY) sea ice throughout most of the Southern Beaufort Sea in the deep water of the Canada Basin. In situ observations found heavily decayed, very small remnant MY and FY floes interspersed with new ice between floes, in melt ponds, thaw holes and growing over negative freeboard older ice. This icescape contained approximately 25% open water, predominantly distributed in between floes or in thaw holes connected to the ocean below. Although this rotten ice regime was quite different that the expected MY regime in terms of ice volume and strength, their near-surface physical properties were found to be sufficiently alike that their radiometric and scattering characteristics were almost identical.
Until the community of cryosphere scientists resolves this apparent overestimation of ice recovery by their standard measurement techniques, claims that the Arctic ice recovered even in 2009 are premature.  The stunning decline in Arctic ice volume in recent years remains very strong evidence of human-caused warming and something the media has every reason to continue to write about in the context of overall global warming stories.


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