The US Environmental Protection Authority has announced that emissions of CO2 and other greenhouse gases are a threat to public health, which opens the way for them to be regulated under the Clean Air Act, a measure once promised by George Bush as a presidential candidate but ferociously resisted by his administration.
As Brad Plumer explains here, the regulations will transform the Congressional debate over bills to introduce a national cap-and-trade system. In the absence of EPA regulations, and assuming continuation of current practices regarding the filibuster, the Republicans in the Senate could block any action as long as they could muster 41 votes (and of course, ratification of a treaty like Kyoto requires 66 out of 100 votes). But now the effect of a filibuster will be to leave the EPA to deal with the issue by regulation, which might include establishment of emissions trading schemes, as well as technological mandates to adopt best practice technology. Almost certainly, some Senate Republicans will prefer a deal where they get to protect some favored interests to a system of regulation over which they have no say.