By Janet Raloff

Web edition: December 7, 2009

In April, the Environmental Protection Agency announced that based on its reading of the science, greenhouse gases threaten public health. Since then, the public and legions of interest groups have weighed in on the subject, shooting EPA some 380,000 separate comments. “After a thorough examination of the scientific evidence and careful consideration of public comments on the ruling,” EPA today reiterated its so-called “endangerment” assessment of greenhouse gases.

This afternoon's announcement paves the way for the agency to regulate greenhouse gases, such as carbon dioxide, under the Clean Air Act. The timing of this pronouncement also appears to signal the Obama administration’s intent to get tough on climate. As tough as Congress will allow, anyway.

Currently, traffic contributes almost one-quarter of total U.S. greenhouse-gas emissions. EPA now intends to finalize greenhouse-gas emissions standards that it proposed earlier this year for new light-duty vehicles (ie cars, SUVs and light-duty trucks). It was part of a joint rulemaking with the Department of Transportation.

The proposed standards are intended to cut U.S. greenhouse emissions by nearly 950 million metric tons – and the use of 1.8 billion barrels of oil – over the life of vehicles built between 2012 and 2016.

“These long-overdue findings cement 2009’s place in history as the year when the United States government began addressing the challenge of greenhouse-gas pollution and seizing the opportunity of clean-energy reform,” EPA Administrator Lisa Jackson said today.