As governor of Massachusetts, Mitt Romney endorsed an aggressive program to reduce the state’s greenhouse gas emissions, pushed to close old coal-fired power plants and embraced wind and solar power. Then came his bids for the Republican presidential nomination, first in 2008 and now in 2012. On climate change as on other issues, he has transformed himself, bit by reactionary bit.

Today he is a proclaimed skeptic on global warming, a champion of oil and other fossil fuels, a critic of federal efforts to develop cleaner energy sources and a sworn enemy of the Environmental Protection Agency.

Mr. Romney has plainly decided that satisfying his party’s antiregulatory base is essential to his political future. But the policies he espouses would be devastating for the country and the planet. If there are doubts on that point, the most recent findings from the International Energy Agency should dispel them: the agency reports an alarming one-year increase in global greenhouse gas emissions, largely because of increasing coal use around the world.

The agency also said that keeping global temperatures below a dangerous threshold is “still within reach” if nations aggressively reduce fossil-fuel consumption while nurturing low-carbon alternatives. And where is Mr. Romney on that? Nowhere.