U.S. President Donald Trump on Thursday announced the revocation of a key 2009 climate determination that has served as the legal foundation for federal climate regulations, including rules on greenhouse gas emissions from motor vehicles and mandates supporting electric vehicle adoption.

Trump and U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin unveiled the decision at the White House, describing it as the "single largest deregulatory action in U.S. history."

"We are officially terminating the so-called endangerment finding, a disastrous Obama-era policy that severely damaged the American auto industry and drove up prices for American consumers," Trump said at a news conference.

The determination, known as the 2009 Greenhouse Gas Endangerment Finding, concluded that carbon dioxide, methane and four other greenhouse gases threaten public health and welfare. It has been used to justify regulations such as vehicle emissions standards and requirements for fossil fuel companies to report their emissions.

"This determination had no basis in fact – none whatsoever. And it had no basis in law. On the contrary, over the generations, fossil fuels have saved millions of lives and lifted billions of people out of poverty all over the world," Trump said.

Former U.S. President Barack Obama said on X that the endangerment finding has served as the basis for limits on tailpipe emissions and power plant rules. "Without it, we'll be less safe, less healthy and less able to fight climate change – all so the fossil fuel industry can make even more money."

"It boggles the mind that the administration is rescinding the endangerment finding; it's akin to insisting that the world is flat or denying that gravity is a thing," Howard Frumkin, professor emeritus of public health and physician at the University of Washington, told AP.

"Health risks are increasing because human-cause climate change is already upon us. Take the 2021 heat dome for example, that killed (more than) 600 people in the Northwest," Dr. Jonathan Patz, physician and director of the Center for Health, Energy and Environmental Research at the University of Wisconsin-Madison, told AP. "The new climate attribution studies show that event was made 150-fold more likely due to climate change."

Trump has long been critical of renewable energy and has even referred to climate change as a "scam."

Last November, the United States skipped the UN annual climate conference held in Belém, Brazil. It was the country's first absence from the meeting in 30 years.

In January 2025, Trump signed an executive order to pull the United States out of the Paris Agreement again, with the exit taking effect on January 27. This marks the second time the U.S. has withdrawn from the agreement, highlighting the deep political divide in the country over climate change.

Earlier this year, Trump also declared that the U.S. would leave dozens of international and UN bodies, including the UN Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change.

The UNFCCC requires wealthy industrialized nations to reduce emissions, implement policies to limit greenhouse gas output, publicly report national emission data, and provide financial support to developing countries to help them address climate change.

(With input from Xinhua)