That assessment followed a 2007 U.S. Supreme Court decision in its landmark Massachusetts v. EPA case that said the EPA has the authority under the Clean Air Act to regulate greenhouse gas emissions and required the agency to make a scientific finding on whether those emissions endanger public health.

In one of its most significant reversals on climate policy to-date, the Trump administration on Tuesday proposed to repeal a 2009 scientific finding that human-caused climate change endangers human health and safety,