Is Snow a Sign of Global Warming?

Image Gallery Rising ocean surface temperatures caused by global warming have increased the temperature and moisture content of the air passing over the United States, thus setting the stage for heavier snow and rainstorms. FLICKR/B ROSEN

Recent heavy snowstorms and cold weather have prompted some commentators to suggest that a cold winter proves global warming isn’t really happening.

Don’t let those naysayers snow you. 

A few snowstorms, cold snaps or even heat waves do not prove anything about climate change, because there is a significant difference between weather and climate. Weather is what we experience on any given day or even over a couple of weeks. Climate describes a region’s prevailing conditions — including such things as temperature, rainfall, wind, humidity and atmospheric pressure — over long periods of time. Climate is a good indicator of what to expect. For example, in the Midwest, one would expect cold winters, whereas in a Mediterranean climate, one would expect a generally milder winter.

Climate change refers to shifts in prevailing conditions observed over decades. One such shift is a long-term rise in global average temperatures. The current cold spells are occurring against this backdrop.

Putting aside the difference between weather and climate, climate change projections show that a warming planet generates more precipitation in areas that typically experience rain or snow. Rising ocean surface temperatures already have increased the temperature and moisture content of the air passing over the United States, setting the stage for heavier snow and rainstorms. An Intergovernmental Panel on Climate Change report found that global warming has increased the frequency of storms that dump heavy precipitation over most land regions that experience storms. Most deserts, conversely, are getting drier.  

“Climate scientists aren’t at all surprised that there are more drenching rain or blizzards in certain parts of the country,” says Dr. Brenda Ekwurzel, a climate scientist with the Union of Concerned Scientists (UCS). “That’s consistent with well-documented climate change trends over the past several decades. Unless we take some dramatic steps to curb global warming, we likely will see a lot more regional precipitation over the next few decades.”