A federal court rejected a claim that the evidence for climate change is too uncertain for the United States government to act on it. The case, Coalition for Responsible Regulation, Inc., et al., v. EPA, involved a challenge to the Environmental Protection Agency's implementation of the Clean Air Act, filed by a number of states and industry groups. The challenge was based, in part, on the idea that the evidence that anthropogenic climate change is a threat to public health and welfare is shaky. A three-judge panel of the United States Court of Appeals for the District of Columbia Circuit found otherwise.
As part of its eighty-two-page decision issued on June 26, 2012, the court wrote (PDF), "The body of scientific evidence marshalled by EPA ... is substantial. EPA's scientific evidence of record included support for the proposition that greenhouse gases trap heat on earth that would otherwise dissipate into space; that this 'greenhouse effect' warms the climate; that human activity is contributing to increased atmospheric levels of greenhouse gases; and that the climate system is warming. Based on this scientific record, EPA made the linchpin finding: in its judgment, the 'root cause' of the recently observed climate change is 'very likely' the observed increase in anthropogenic greenhouse gas emissions" (pp. 28-29).
As The New York Times (June 26, 2012) summarized, "The judges unanimously dismissed arguments from industry that the science of global warming was not well supported and that the agency had based its judgment on unreliable studies. 'This is how science works,' they wrote. 'The E.P.A. is not required to reprove the existence of the atom every time it approaches a scientific question.'" The Times added, "The plaintiffs could still ask for a hearing by the full appeals court or decide to appeal to the Supreme Court, but it is not clear whether they will do so, given the emphatic nature of the decision."