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Global warming is about changes in long-term averages and not about single events; it does not mean an end to cold weather. Instead, it means that cold weather will become less frequent and hot weather more frequent when averaged over decades. In fact, both of these trends have been observed over the past 50 years in the United States and globally. Even with global warming, we will have cold winters; however, there will be fewer of them. It is also important to remember that a cold winter for one location doesn’t mean a cold winter everywhere. In fact, many parts of the world, including the Arctic and the tropics, had an unusually warm winter in 2010.
To create heavy snowfall the East Coast experienced during the 2009 and 2010 winters, you need two things: moist air and cold air. In recent winters, the Gulf of Mexico and the tropical Pacific have supplied lots of moist air, and that is the key to getting heavy precipitation. We also had more cold air than usual that spilled out of the Arctic. Conditions were just right in the past two winters for these air masses to meet up and create massive snowstorms. Snowfall occurs when warm, moist air is forced above the cold air and begins to precipitate into the cold air, causing what would haven rain to freeze. Since climate change increases the moisture content of the atmosphere, global warming can actually increase the risk of heavy snowfall.
Source: Center for Climate and Energy Solutions