Supreme Court of the United States Nº 05–1120

Based on respected scientific opinion that a well-documented rise in global temperatures and attendant climatological and environmental changes have resulted from a significant increase in the atmospheric concentration of “greenhouse gases,” a group of private organizations petitioned the Environmental Protection Agency (EPA) to begin regulating the emissions of four such gases, including carbon dioxide, under §202(a)(1) of the Clean Air Act, which requires that the EPA“shall by regulation prescribe . . . standards applicable to the emission of any air pollutant from any class . . . of new motor vehicles . . . which in [the EPA Administrator’s] judgment cause[s], or contribute[s] to, air pollution . . . reasonably . . . anticipated to endangerpublic health or welfare,” 42 U. S. C. §7521(a)(1). The Act defines “air pollutant” to include “any air pollution agent . . . , including any physical, chemical . . . substance . . . emitted into . . . the ambientair.” §7602(g).