The U.S. Energy Information Administration reported on Friday:

… coal’s share of monthly power generation in the United States dropped below 40% in November and December 2011. The last time coal’s share of total generation was below 40% for a monthly total was March 1978. A combination of mild weather (leading to a drop in total generation) and the increasing price competitiveness of natural gas relative to coal contributed to the drop in coal’s share of total generation.

It’s a tad ironic that warming weather, driven in part by coal-fueled emissions, contributed to the drop in coal use.

Another reason for the steady decline in coal power is that the Sierra Club, with the support of centrists like Mayor Michael Bloomberg of New York, is working to shut down all U.S. coal plants in the Beyond Coal campaign.