Northern Hemisphere Snow Cover Drops to Record Low for Month of May

Rutgers University's Global Snow Lab (GSL) reports that snow cover in May dropped to the lowest level on record (since 1966) for the month over the Northern Hemisphere.  The mean snow cover for the Northern Hemisphere in May from 1966 through 2010  is 19.5 million square km (7.5 million square miles).  This May, however, the extent dropped to 15.2 million square km (5.9 million square miles). 

That is a departure of 4.3 million square km (1.7 million square miles) -- or 22% -- below the mean.  That departure from the mean is roughly equivalent to the areas of the eight largest U.S. states combined (Alaska, Texas, California, Montana, New Mexico, Arizona, Nevada and Colorado).

As the figure below indicates, the May snow cover continues the trend of declining snow cover in May for the Northern Hemisphere.  Similarly, there is a declining trend for Spring (March, April, and May) snow cover, though the spring snow extent did not break the record (see here).  Spring 2010 had the fourth lowest snow extent on record over the Northern Hemisphere.

The figure below shows that the negative snow cover anomaly was widespread, with record low levels in both North America and in Eurasia.  In the image, browns show area where snow extent was below the mean while blue colors show snow cover that is above the mean.

Last winter, climate change denialists deceptively and loudly claimed that heavy snows in some areas of the northern hemisphere somehow meant the climate change was not happening.  Comedian Bill Maher recently said such conclusions were "like saying the sun might not be real because last night it got dark. And my car's not real because I can't find my keys."  See also Colbert mocks Fox News for using snowstorm to deny global warming, posted at Climate Progress on 12 February 2010.

The denialists thus far have not commented on the record low snow cover this May -- and on the longer term declines for both May and Spring snow cover.

Online Resources:

Rutgers University's Global Snow Lab.