[JURIST] US Environmental Protection Agency (EPA) Administrator Stephen L. Johnson [official profile] Friday signed a notice [PDF text] for submission to the Federal Register explaining the agency's reasons for denying California's request for a waiver [JURIST news archive, EPA backgrounder] that would have allowed it to impose stricter greenhouse gas emissions standards on cars and light trucks. Johnson wrote:

It is true that many of the effects of global climate change (e.g. water supply issues, increases in wildfires, effects on agriculture) will affect California. But these effects are also well established to affect other parts of the United States. Many parts of the United States may have issues related to drinking water (e.g., increased salinity) and wildfires and effects on agriculture are by no means limited to California. These are issues of national, indeed international, concern and Congress has indicated that such conditions do not merit separate standards in California unless the conditions are sufficiently different in California compared to the rest of the nation as a whole. In my judgment, the impacts of global climate change in California, compared to the rest of the nation as whole, are not sufficiently different to be considered “compelling and extraordinary conditions” that merit separate state GHG standards for new motor vehicles.

Critics have argued that California does in fact face unique global warming problems due to its already warm climate and diverse wildlife and that higher emissions standards are therefore warranted.

In December 2007, the EPA denied [rejection letter, PDF; JURIST report] California's waiver request, with Johnson saying that a unified national standard for greenhouse gas regulation was preferable to a state-by-state network of regulations and pointing to the Energy Independence and Security Act of 2007 [HR 6 materials; WH fact sheet], signed into law that month by President George W. Bush. California filed suit [JURIST report] in January to challenge the denial. AP has more. Dow Jones has additional coverage.