Dr. James Hansen, a climate scientist and the head of NASA's Goddard Institute for Space Studies--who is probably best known for reporting that the White House was editing NASA press releases to downplay global warming--joined 10 other scientists in filing an amicus brief with the Supreme Court encouraging the Court to review the decision of the Court of Appeals for the D.C. Circuit in Massachusetts v. EPA, 415 F.3d 50 (D.C. Cir. 2005).
Massachusetts, and the other petitioners in that case argued that argued that the EPA must regulate greenhouse gas emissions from motor vehicles. They further argued that the EPA could not avoid its responsibility because of "scientific uncertainty" surrounding climate change. There, the court found it was within the EPAs discretion not to regulate such emissions. The petitioners have now appealed to the Supreme Court to for review.
The Clean Air Act provides:
The Administrator shall by regulation prescribe...standards applicable to the emission of any air pollutant from any class or classes of new motor vehicles or new motor vehicle engines, which in his judgment cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare." 42 U.S.C. § 7521(a)(1)
The amici argue that, while that language does give the EPA administrator some discretion, that discretion is limited to asking 1) do the emissions cause air pollution and 2) do the emissions endanger public health or welfare. If so, the EPA must regulate the emissions. The appeals court, on the other hand, held that "Congress does not require the Administrator to exercise his discretion solely on the basis of his assessment of scientific evidence...policy judgments also may be taken into account."
The amici also argue that the United Nations Framework Convention on Climate change (which, unlike Kyoto, the U.S. has ratified), specifically says that "lack of full scientific certainty should not be used as a reason for postponing [measures to mitigate climate change]"