photo: Michael Dolan/Creative Commons
The link between extreme weather and climate change, including heavy snowfall even though global temperatures continue to climb, has been made again and again by scientists. The most recent iteration comes from the Union of Concerned Scientists. TreeHugger has covered the science of this a number of times, so I'll just pass on the relevant quotes: Weather Underground's Jeff Masters reminds us (with my emphasis),
Heavy snowstorms are not inconsistent with a warming planet. In fact, as the Earth gets warmer and more moisture gets absorbed into the atmosphere, we are steadily loading the dice in favor or more extreme storms in all seasons, capable of causing greater impacts on society.
As the climate continues to warm we should expect an increase in heavy snow events for a few decades, until the climate grows so warm that we pass the point where it's too warm for it to snow heavily.
We are also experiencing spring creep, where the warmer than average temperatures are shortening the length of winter. For instance, we're now seeing spring runoff in the mountains in the western US starting one to three weeks earlier than 60 years ago.
Nipping one in the bud: Climate change won't turn January in the northeast US into June.
Masters cites the unusual nature of this winter's snowfall, pointing out that Only once in the past 50 years (in 1960-61) have there been three storms in one season hitting Category 3 or worse on the Northeast Snowfall Impact Scale. This year New York City experience its two snowiest months on record, with January and February each getting 3' of snow. Minnesota, South Dakota, and North Dakota all had near-record snowfall.