The first major threshhold of irreversible climate change seems to have been crossed. Things are probably never going back to “normal” in the Arctic. This may have large consequences.
The international Polar Year has issued a press release entitled
As predicted by all IPCC models, Arctic sea ice will most likely disappear during summers in the near future. However, it seems like this is going to happen much sooner than models predicted, as pointed out by recent observations and data reanalysis undertaken during IPY and the Damocles Integrated Project.
Providing an object lesson of one of our main themes:
No, that is not a reason to relax and forget the whole thing.
That is a reason to be more worried than the models indicate.
The entire Arctic system is evolving to a new super interglacial stage seasonally ice free, and this will have profound consequences for all the elements of the Arctic cryosphere, marine and terrestrial ecosystems and human activities. Both the atmosphere and the ocean circulation and stratification (ventilation) will also be affected. This raises a critical set of issues, with many important implications potentially able to speed up melting of the Greenland ice sheet, accelerating the rise in sea levels and slowing down the world ocean conveyor belt (THC). That would also have a lot of consequences on the ocean carbon sink (Bates et al. 2006) and ocean acidification. Permafrost melting could also accelerate during rapid Arctic sea-ice loss due to an amplification of Arctic land warming 3.5 times greater than secular 21st century climate trends, as pointed out recently by Lawrence et al. (2008). This permafrost evolution would have important consequences and strong impacts on large carbon reservoirs and methane releases, either in the ocean and/or on land.
Are we having fun yet?
Update 3/14: Similar news out of Copenhagen.