In two sharply diverging opinions, the Fifth Circuit Court of Appeals and a northern California district court recently considered the validity of common law tort claims against large emitters of greenhouse gases. The Fifth Circuit, in Comer v. Murphy Oil USA, held that plaintiffs had standing and that their claims did not present a nonjusticeable political question. The district court, in Native Village of Kivalina v. ExxonMobil Corporation, found that plaintiffs lacked standing because their injuries were not traceable to defendants' actions, and that their claims were barred by the political question doctrine.

Comer is generally consistent with the Second Circuit's recent opinion in Connecticut v. American Electric Power Company Inc., ____F.3d ____, No. 05-5104 (2nd Cir. 2009), although the Fifth Circuit did not rely on that case. Kivalina, on the other hand, explicitly criticized the reasoning of American Electric, setting the stage for a potential circuit split if the Ninth Circuit upholds the district court's decision.