Firstly the UK Parliament has had some sessions recently that I think are a must-see for Arctic climate change nuts. I've not learned much new from the sessions, but it's good to see the sort of points being made here and on other blogs being aired before a select committee, as part of the series of sessions entitled "Protecting the Arctic".
Session on 21/9/12. Prof Peter Wadhams and Prof Tim Lenton, scientists working on the Arctic, join John Nissen of the Arctic Methane Emergency Group in providing evidence before the enquiry.
Session on 14/3/12. Prof Julia Slingo OBE, Chief Scientist at the UK Met Office, gives evidence during the first 20 minutes. I must admit I got bored by the evidence from Shell and Cairn Energy so didn't watch it.
There are other sessions, but these seemed to be the most noteworthy. For more search for "Protecting the Arctic" from January to the present date from the search page here.
In essence the four participents fall equally into two camps: Peter Wadhams and John Nissen being concerned about East Siberian Shelf methane and a rapid transition (within years) to a summer with very little sea-ice. Tim Lenton doesn't express a view as to when we will see an open Arctic Ocean (unless I missed it), however his opinion is in line with Julia Slingo on methane - chronic not catastrophic. I'm particularly impressed by how Julia Slingo's views concur with my own as stated earlier on this blog, we seem to have been reading the same papers. One area where I disagreed with what she said was the implied attribution of the Petoukhov/Semenov mechanism in the Winters of 2009/10 and 2010/11, with regards the former I still think Cohen's explnation fits best. I may end up disagreeing on the imminence of a seaonally sea-ice free Arctic, but I'm now waiting until the Spring PIOMAS results are in to see if I'm going to change my mind on that.
Secondly, and finally, I've read Dr Jennifer Francis and Dr Steve Vavrus's paper entitled "Evidence Linking Arctic Amplification to Extreme Weather in Mid-Latitudes." Abstract. It's well worth reading, clear and succinct. In a nutshell, to quote from the conclusion:
In summary, the observational analysis presented in this study provides evidence supporting two hypothesized mechanisms by which Arctic amplification – enhanced Arctic warming relative to that in mid-latitudes – may cause more persistent weather patterns in mid-latitudes that can lead to extreme weather.
One effect is a reduced poleward gradient in 1000-500 hPa thicknesses, which weakens the zonal upper-level flow. According to Rossby wave theory, a weaker flow slows the eastward wave progression and tends to follow a higher amplitude trajectory, resulting in slower moving circulation systems...
The second effect is a northward elongation of ridge peaks in 500 hPa waves, which amplifies the flow trajectory and further exacerbates the increased probability of slow-moving weather patterns...
Essentially it's the same material covered in the lecture by Dr Fancis that I covered back in January, link, see the last comments that page for requests for pre-print copy. So we're seeing a growing pattern of evidence linking the loss of Arctic sea-ice to changes in mid-lattitude weather. As Dr Francis puts it:
The question is not whether sea-ice loss is affecting large-scale atmospheric circulation, it's 'how can it not?'