On Tuesday, the Bush administration filed a brief defending the EPA’s refusal to regulate greenhouse gas emissions from automobiles, proving once again the administration is stuck in a Stone Age of environmental science. The EPA is hiding behind a narrow interpretation of language in the Clean Air Act (CAA) to avoid taking meaningful steps toward reducing greenhouse gas emissions. The agency claims nuances in the legislation describe their role in curbing greenhouse gases as “nonregulatory,” thereby absolving them from responsibility. However, this is at odds with language elsewhere in the CAA: 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. [Section 202(a)(1)] The growing presence of greenhouse gases is one of the gravest environmental threats of our time. EPA has a responsibility under the Clean Air Act to protect our health and environment from the impacts of greenhouse gas emissions. Industry alone cannot be expected to reduce emissions without regulatory intervention.