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05 May 2010

Pollution Speeds Up Snow Melt In Europe, Asia

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NSF-supported climate scientist Mark Flanner and colleagues find differences in the rates for spring warming and snow cover decline in Eurasia and North America, and are studying whether aerosols are a key factor

Over the past 30 years, springtime snow melt and warming appear to be proceeding at a faster rate in Eurasia than in North America.

Climate scientist Mark Flanner, an assistant professor at the University of Michigan and a recent Advanced Study Program graduate at the National Science Foundation's (NSF) National Center for Atmospheric Research (NCAR), led a study that investigated these changes, ultimately finding that spring warming rates and snow cover decline in Eurasia may be twice what they are in North America.

In the same study, Flanner and his colleagues also pointed out that only one of the climate scenarios generated by general circulation models in the Intergovernmental Panel on Climate Change's (IPCC) Fourth Assessment Report reflected this trend.

In fact, most IPCC model scenarios show the regions having similar springtime temperatures and snow-melt rates. Flanner and his collaborators suspect aerosols--particularly black carbon and mineral dust--might be responsible for the difference in modeled versus observed climate.

Eurasia produces high levels of both types of aerosols, which blow across the Eurasian land mass and affect the surface and nearby atmosphere in a variety of ways.

Some aerosols reflect incoming solar energy, potentially cooling underlying surfaces, but black carbon and mineral dust tend to warm snow-covered surfaces by absorbing incoming solar energy. Particulates that fall to the surface also reduce snow's reflective qualities, causing even more radiation to be absorbed.

In the Northern Hemisphere, springtime snow cover is unique because of its widespread distribution, and because intense incoming solar radiation during that season amplifies atmospheric aerosols' effects.


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