SEARCH BLOG: GLOBAL WARMING
After two fairly cold winters in a row, 2011-12 has started out very mild over a large part of the U.S. Here in SE Michigan, there is no snow and the lake ice, if present, is exceedingly thin. Last year, there were ice fisherman on our lake in early December and fairly deep snow from then through most of the winter. Obviously, the change is much too fast for a climate change... although as pleasant as this winter has been so far, we wouldn't object to a more permanent change in that direction. Of course, if you are a ski bum or can't wait to get out on the snowmobile, this is not change for the better.
What happened? From the National Snow and Ice Data Center [NSIDC]:
The past two Arctic winters were dominated by a negative phase of the Arctic Oscillation, a large-scale weather pattern that brings generally warm conditions to the Arctic and colder conditions to Europe and North America. In contrast, the winter of 2011 has so far seen a mostly positive phase of the Arctic Oscillation. While temperatures were above normal in the Kara and Barents seas, the positive phase of the Arctic Oscillation tends to keep the coldest winter air locked up in the Arctic, which keeps the middle latitudes free of frigid Arctic temperatures and strong snowstorms. This weather pattern helps to explain the low snow cover and warm conditions over much of the United States and Eastern Europe so far this winter.
Separately, the NSIDC explains the phenomenon this way: