Yesterday, the US Supreme Court ruled 8-0 that the Clean Air Act displaces the federal common law of nuisance with respect to climate change and its mitigation. (You can read the opinion here). Justice Sotomayor did not take part in the decision; she had sat on the appellate panel below, but was not a party to that court's ruling.
Most scholars expected this result. In fact, I doubt whether more than a few were surprised that it was a unanimous decision. Many environmentalists will not be pleased that state and private plaintiffs cannot sue power plants and other large carbon emitters for nuisance. It certainly reduces the incentive large emitters have to seek a federal solution as a means of reducing common-law exposure. However, the prospect of controlling greenhouse gas emissions through nuisance law has always struck me as both haphazard and too costly, relative to a well-designed regulatory scheme (which still isn't in place).
Perhaps more important than the Court's ruling on the merits, going forward, is the Court's strong reaffirmation of Massachusetts v. EPA. As Dan Farber explains (here), Justice Sotomayor, voting in subsequent cases, would make a clear 5-vote majority on issues of standing and the political question doctrine.