Current statistics underscore Bloomberg’s speech, with coal-fired plants providing only 35% of U.S. electricity needs in 2012—down from 44% in 2011. Hostile regulations from Washington, bankruptcies and intense competition from natural gas are just part of the picture.

“It used to be coal is king, and regrettably coal remains king in nations like India and China,” added the mayor. “Here in the U.S., I am happy to say, the king is dead; coal is a dead man walking.”

Bloomberg’s donations have gone to the Sierra Club’s “Beyond Coal” campaign that claims to have shut down 150 coal-fired power plants through litigation and local activism. Bloomberg’s $50 million donation represents one-third of $150 million budget for the movement that seeks to shutter as many as one-third of the nation’s oldest coal-fired power plants by 2020.