The Obama administration has opened the way to regulating US greenhouse gas emissions by declaring climate-warming pollution a danger to human health and welfare.
The Environmental Protection Agency said greenhouse gases in the atmosphere endanger the welfare of both current and future generations, and that human activities spur global warming.
Congress is already considering a bill to cut emissions of carbon dioxide, which is emitted by cars, coal-fired power plants and oil refineries, among other sources. It would introduce a cap-and-trade system, which would let those companies that emit more than the limit buy credits from those that emit less.
President Barack Obama would prefer legislation over administrative action to curb greenhouse emissions, the White House said.
The EPA's endangerment finding said high atmospheric concentrations of greenhouse gases "are the unambiguous result of human emissions, and are very likely the cause of the observed increase in average temperatures and other climatic changes."
The finding is essential for the US government to regulate climate-warming emissions like carbon dioxide under the Clean Air Act. Regulation is not automatically triggered by the finding, as there will be a 60-day comment period.