At last, a little more clarity on what the EPA is planning to do in terms of greenhouse-gas regulations. (Riveting topic, huh?) Last Friday, West Virginia's Jay Rockefeller and seven other Senate Democrats from coal states sent a letter to EPA head Lisa Jackson expressing "serious economic and energy security concerns" about the agency's plans to regulate carbon-dioxide and other heat-trapping gases on its own. (If you missed it, here's a primer on what those EPA rules would likely entail.)

So that prompted Jackson to fire off a response today, laying out the EPA's likely timetable for moving forward. In her letter, she explained that the agency's regulations for power plants and industrial facilities would phase in slowly, starting in 2011. Only about 400 plants would have to apply for permits by the first half of next year—and that just includes those plants that already have to apply for permits for non-greenhouse-gas emissions. After that, the largest polluters—facilities that emit more than 25,000 tons of CO2 per year—would start getting regulated between 2011 and 2013. Smaller polluters, meanwhile, wouldn't get regulated until at least 2016.

Jackson also told Rockefeller et. al. that if Congress ended up blocking the EPA's authority over greenhouse gases, that would imperil the fuel-economy rules that the Obama administration drew up alongside the states and automakers last year. At our TNR energy event today, White House climate adviser Carol Browner said much the same thing. And if the national fuel-economy rules fall apart, that means we'd almost certainly go back to the earlier system where California is pushing ahead with tighter standards that are different from other states—a patchwork approach that car companies all seem to hate.

In any case, some of those coal-state Dems seem to be partly mollified by the EPA's relatively slow timetable. "It helps," said Rockefeller, although he noted that he may want to pass legislation that pushes back the agency's timetable back even more, in order to give Congress enough time to pass a climate bill of its own. (Of course, if Congress passes a climate bill this year, Jackson's timetable won't be a problem.) That said, none of those Dems concerned about the EPA's plans sound like they're quite ready to join Lisa Murkowski's efforts to nullify the agency's authority over greenhouse gases.

(Flickr photo credit: willstegerfoundation)