The Clean Air Act gives the Environmental Protection Agency the duty to regulate carbon dioxide emissions, and the Obama administration has been using this authority in a number of important ways over the years. What it hasn't yet done are promulgate regulations on existing sources of climate pollution rather than on hypothetical new sources. One reason it hasn't done that is that for a long time nobody could really think of an economically feasible way to do this. Just shutting down random power plants would be extremely disruptive. But back last winter I wrote about a very clever strategic outline from the Natural Resources Defense Coucnil that paints a path forward for using this power in a way that would give states more flexibility in terms of how to reduce emissions, while still making huge progress on climate issues.
Jon Chait has recently revived interest in this issue among generalist pundits by arguing that Obama not only can but probably will do this.
When I first wrote about the topic, I said I thought it had the proverbial snowball's chance in hell of actually happening. That was perhaps overly strong language, but I'm still skeptical. The administration's attitude toward the Keystone XL pipeline does not strike me as that of a group of people prepared to use any means necessary to reduce greenhouse gas emissions. But I've come to think that arguing over predictions is one of the least-useful possible uses of a writer's time, so I think the important point is simply that Obama can use this authority to end up with a much more substantive climate legacy than most people are currently penciling in for him. The roadmap exists, and the question is whether it's going to be used.