Forty nine states have snow on the ground right now thanks to a rash of snowstorms caused, in part, by human-induced climate change (.pdf, 1.8 MB). First, the situation on the ground:
The extraordinary rash of snowstorms which have swept the U.S. in recent weeks, many generating record snowfall, have produced one of the country's most expansive snow packs in recent memory. National Weather Service researchers charged with monitoring the country's snow cover and its water content estimated Friday that more than 67% of the Lower 48 sat beneath a veil of snow. Hawaii, despite the presence of mountains which can and often do become snow-covered in winter, is the only state not to report at least some snow on the ground. The snow has been so widespread in recent weeks, even perennially snow-free Florida has failed to escape. De Funiak Springs, in the state's panhandle near the Georgia border, reported a 1" snow accumulation late Friday afternoon at the same time a thundery squall line in warmer air to the south was diving southward the length of the Florida peninsula unleashing driving rains and 70 mph gusts.
And the prediction the National Climatic Data Center summarized on their Climate Change FAQ page:
In some areas where overall precipitation has increased (ie. the mid-high northern latitudes), there is evidence of increases in the heavy and extreme precipitation events. Even in areas such as eastern Asia, it has been found that extreme precipitation events have increased despite total precipitation remaining constant or even decreasing somewhat. This is related to a decrease in the frequency of precipitation in this region.
Now, I'm not a physicist, but I do understand that putting the same amount of energy into a system while cutting off the avenues for the energy to dissipate means more energy remains in the system, like having a slow drain in a bathtub. All the evidence might support a different conclusion, of course, which is why scientists are looking for more evidence. Maybe climatologists are wrong. Maybe we're not experiencing an unprecedented shift in worldwide climate, and maybe we didn't cause it. At the moment, though, that's wishful thinking.