On 12 February, US president Donald Trump revoked the “Endangerment Finding”, the bedrock of federal climate policy.

The 2009 finding concluded that six key greenhouse gases, including carbon dioxide (CO₂), were a threat to human health, triggering a legal requirement to regulate the gases and the subsequent rollout of policies such as federal emission standards for vehicles, power plants, factories, and other sources.

In a statement issued by the EPA, Administrator Lee Zeldin said the endangerment finding had been “the source of 16 years of consumer choice restrictions and trillions of dollars in hidden costs for Americans” and that its elimination  ̶- the “largest deregulatory action in U.S. history”  ̶  would save American taxpayers over $1.3 trillion.

While the revocation is expected to face multiple legal challenges, it will have a profound impact on federal emissions regulations should these challenges fail.

Carbon Brief has published an analysis of the endangerment finding including its effect on US climate policy in the past and the potential implications of the repeal going forward. Read it here.

Further commentary: Winners and losers from the rollback of US climate policies

Read also: Analysis: Trump has overseen larger coal decline than any other US president