After another extreme winter in the eastern United States – symbolized by Boston’s historic snow blitz of 90 inches in just over three weeks – scientists, the media and the public are asking once again: Is climate change causing more extreme snowfall events? The argument that climate change is leading to greater snowfalls is based on a very simple law of physics – a warmer atmosphere can hold more moisture. But on the other hand, snowfall is dependent on sub-freezing temperatures, so what does it mean for places like the eastern United States, where climate change might make it too warm for snowfall? The best tools we have to answer such a complex question, which incorporate all the physics and competing factors, are the climate models. Put simply, climate models are similar to weather models but run on a much larger scale in both space and time. They take into account interactions between land, oceans and ice, and importantly, they attempt to predict changes in our climate as greenhouse gases increase in the atmosphere. All of the climate models predict that mid-latitude storm tracks (like the winter storms we see in the United States) will shift toward the poles with climate change — north in the Northern Hemisphere, and south in the Southern Hemisphere. They also predict more precipitation overall. However, with a more northward storm track and warmer temperatures, the precipitation increase actually leads to more rainfall and less snowfall for the Northern Hemisphere mid-latitudes in winter, including the eastern United States. The models predict an increase in snowfall across parts of the Arctic, and in particular Siberia, where temperatures for much of the year are well below freezing and where an atmosphere with more moisture can more than compensate for warmer temperatures. But contrary to the predictions of the climate models, recent winters, especially since 2009-2010, have produced some historic snowstorms and seasonal totals in the Northeast. So, despite being much warmer now, the large cities in the Northeast are seeing an increase in snowfall, similar to the model projections for Siberia. Once-moderate snowfalls are now blockbuster snowstorms instead, pushing both storm and seasonal snow totals higher. So are the models wrong? Does climate change actually result in an increase in snowfall? More via The Washington Post.
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