It was not that long ago that those who believe (on faith, not scientific fact) that there is no global warming, celebrated the snowfall in the Eastern U.S. as though it showed that global warming was not happening. Prior posts have reviewed a number of reasons why global warming is not preceding as rapidly as many hypothecated; they have also reviewed the evidence of global warming as reflected in changing patterns of animal migration, droughts in various parts of the country, etc. Ironically, the increased snowfall may support the models of global warming, even though (as noted in prior posts) they are often flawed predictive tools.
Most models have indicated that global warmings first temperature increases would occur in the far North and far South. As noted in prior posts, this is in fact happening; the measurements provide hard evidence that global warming is occurring. Like all things global, such increases are not uniform across a region, but as noted in prior posts there are some amazingly large increases in North and South polar regions that support the global warming models. Another irony of the ignorance of those who deny global warming is that polar warming may actually mean more snow in the Northern Hemisphere. But, how can that be? Were their celebrations an act of ignorance? Possibly so.
Despite rising global temperatures, extreme winters have blasted much of the Northern Hemisphere during the last decade. Unusually large snowstorms have pummeled the United States' east coast during the winters of 2009 to 2010 and 2010 to 2011. Parts of Japan saw record levels of snow this winter (2011-2012), while in Europe both the Danube and Venice's canals froze over, a rare sight. To explain this bitter cold and snow, some scientists have not unreasonably turned to natural climate fluctuations, including El Niño, a periodic warming of the eastern Pacific Ocean thought to portend warmer and drier winter conditions; but since some severe winters coincided with El Niño years, this explanation made no sense. Researchers thus looked instead to sea ice floating in the Arctic, a region that has been warming twice as quickly as the average rate for the Northern Hemisphere (a fact reflective of a number of climate models, those flawed engines of prediction that have been criticized frequently in prior posts).
Satellite observations show that the amount of sea ice during autumn months, after the summer melt, declined by 27.3% between 1979 and 2010. In its worst year, 2007, sea ice covered 4.13 million square kilometers in September, down 1.19 million square kilometers from the previous record low in 2005. Years with less autumn ice tended to be followed by more winter snow in many parts of the Northern Hemisphere. The researchers' computer simulations suggest that losing 1 million square kilometers of ice can increase snowfall by 3 to 12% in some places, including parts of the United States, Europe and China. So, an association has been established. But, what is the causal connection?
Researchers have been studying the atmosphere to work out how changes in sea ice could chill faraway places. When the reflective ice disappears, the darker ocean that remains absorbs more of the sun's energy. Both the surface of the water and the air above it heat up, changing the way that winds circulate through the atmosphere and forming a high-pressure system. Computer simulations published in 2009 found that such a pressure system can push cold air out of the Arctic and into Eurasia. A case study of Europe's 2005-2006 winter, reported in 2010, suggested that cold air blowing in from the Arctic increases by threefold the chance of cold winter extremes in Europe.
Disappearing sea ice may also provide more moisture for forming snow. In further simulations, open water no longer covered by ice released vapor that traveled to parts of Europe and Asia. But, other researchers have expressed doubt that this humidity plays much of a role. Most of the United States would have abnormally low humidity during the winter, in precisely the areas where lots of snow falls. Critics argue that whether there is enough moisture to cause heavy snowfall during a cold interval is probably controlled by other factors. They note that disappearing sea ice is not the only thing driving the cold and the snow. The United States had a particularly warm and snowless winter this year, probably thanks to a periodic flip in Arctic winds that trumped the effects of sea ice loss.
Still, if sea ice melts further, the supporters of the association believe that big snowstorms may be in the forecast more often than not. If this pattern of reduced sea ice continues, in the short term there will be more cold, snowy conditions, believe those who support the sea ice-snow model.
As I frequently say, stay tuned. There is only one conclusion that can be drawn so far. Major snowfalls in the Winter in the Eastern U.S. do not mean that global warming is a flawed theory.
Studies of this issue can be found at: http://www.pnas.org/content/early/2012/02/17/1114910109; http://www.tellusa.net/index.php/tellusa/article/view/11595/html; http://www.agu.org/pubs/crossref/2010/2009JD013568.shtml; & http://www.agu.org/pubs/crossref/2009/2008GL037079.shtml.
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