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there are better explanations than the legendary Gulf Stream breakdown for the current coolish autumn.

My first stop on climate questions is always the excellent RealClimate, collective blog of the "hockey team" (i.e. the Hansen crowd)

That pointed me here, to a much more plausible mechanism for global warming causing the cold weather : a combination of the North Atlantic Oscillation and an exceptionally low level of sea ice in the eastern Arctic :

Typically cold weather in northern Europe is associated with the NAO which consists of a high pressure system over the Azores and a low pressure system over Iceland. The so-called negative phase of the NAO was particularly strong during the second half of November, according to Petoukhov. The NAO is the dominant mode of atmospheric variability in the north Atlantic throughout the year and particularly prominent in the winter. The pressure difference drives the winds and the weather fronts.
[...]
"We had a strong negative phase of the NAO in the second half of November. The pressure gradient between the Azores high and the Icelandic low was very small. This is the favourite situation for cold winters

So, we have the NAO which is an apparently random/cyclical type thingy, giving us a bit of a chill this year... But there's more!

Warming oceans, thought by many to be associated with climate change, are contributing to reductions in sea ice in the Arctic area. Computer models suggest that a reduction in sea ice in the eastern Arctic leads to a loss of ocean heat and a consequent warming of the lower atmosphere which can trigger atmospheric circulation anomalies that can in turn lead to an overall cooling of northern continents, according to Petoukhov's research which was published in the Journal of Geophysical Research in November. This can result in a continental-scale winter cooling reaching, on average, −1.5C colder than it would otherwise have been.
[...]
"Just yesterday I checked the sea ice in the Barents-Kara and it was very low. Nearly as low as it was between 2005 and 2006," Petoukhov told Reporting Climate Science .Com on 2 December 2010.

The strong diminishing trend in Arctic sea ice, particularly when it is accentuated in the Barents sea, gives us colder winters. This year it looks like we get the Quinella.

This correlation between the sea ice reduction and the continental cooling is strong, according to the research. Other explanations linking cold winters and global warming include reduced solar activity and changes in the Gulf Stream are less strongly correlated. However, the NAO could interact with sea-ice decrease, the study concludes and one could amplify the other. This is what may be happening at the moment, suggested Petoukhov.

If the Gulf Stream gets messed up as well, that would be the Trifecta. But even without it, I think we'll have a very cold winter.

Footnote : I was hoping to do a bit of early skiing this weekend with the kids... but it's a tepid 15° today, and it's all turned to mush. The joys of a semi-continental climate.

It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II

by eurogreen on Wed Dec 8th, 2010 at 10:18:05 AM EST

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