On February 10, the Environmental Protection Agency said it would ditch its “endangerment finding”—the mechanism that allows the government to regulate climate pollution. It’s “the single biggest attack in U.S. history on federal authority to tackle the climate crisis,” Manish Bapna, president and CEO of the environmental nonprofit Natural Resources Defense Council, said in a recent press briefing. Here’s a brief primer on what the rule is and what the repeal might mean.

In 2009, the EPA issued a ruling saying that six greenhouse gases—including carbon dioxide and methane—were a danger to public health and welfare, citing a mountain of scientific evidence. The EPA issues similar “endangerment findings” for every pollutant it regulates,........

© Fast Company