Predicting the weather

And interesting explanation of factors that affect the weather, and why declining arctic ice from global warming can cause cooler winters in the U.S.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1965

NOAA's annual Arctic Report Card discussed the fact that recent record sea ice loss in the summer in the Arctic is having major impacts on winter weather over the continents of the Northern Hemisphere. The Report Card states, "There continues to be significant excess heat storage in the Arctic Ocean at the end of summer due to continued near-record sea ice loss. There is evidence that the effect of higher air temperatures in the lower Arctic atmosphere in fall is contributing to changes in the atmospheric circulation in both the Arctic and northern mid-latitudes. Winter 2009 - 2010 showed a new connectivity between mid-latitude extreme cold and snowy weather events and changes in the wind patterns of the Arctic; the so-called Warm Arctic-Cold Continents pattern...With future loss of sea ice, such conditions as winter 2009 - 2010 could happen more often. Thus we have a potential climate change paradox. Rather than a general warming everywhere, the loss of sea ice and a warmer Arctic can increase the impact of the Arctic on lower latitudes, bringing colder weather to southern locations." As a specific example of what the Report Card is talking about, Francis et al. (2009) found that during 1979 - 2006, years that had unusually low summertime Arctic sea ice had a 10 - 20% reduction in the temperature difference between the Equator and North Pole.

This resulted in a weaker jet stream with slower winds that lasted a full six months, through fall and winter. The weaker jet caused a weaker Aleutian Low and Icelandic Low during the winter, resulting in a more negative Arctic Oscillation (AO), allowing cold air to spill out of the Arctic and into Europe and the Eastern U.S.

Thus, Arctic sea ice loss may have been partially responsible for the record negative AO observed during the winter of 2009 - 2010, and strongly negative AO last winter. If the Arctic Report Card is right, we'll be seeing more of this pattern during coming winters--possibly even during the winter of 2011 - 2012, since Arctic sea ice loss this year was virtually tied with 2007 as the greatest on record.

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tags: Arctic Oscillation, North Atlantic Oscillation, sunspot cycle, La Niña
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