WASHINGTON (AP) — The Trump administration on Thursday will revoke a scientific finding that long has been the central basis for U.S. action to regulate greenhouse gas emissions and fight climate changethe White House announced.

The Environmental Protection Agency will issue a final rule rescinding a 2009 government declaration known as the endangerment finding. That Obama-era policy determined that carbon dioxide and other greenhouse gases endanger public health and welfare.

President Donald Trump and EPA Administrator Lee Zeldin will “formalize the rescission of the 2009 Obama-era endangerment finding” at a White House ceremony, White House press secretary Karoline Leavitt said Tuesday.

The action “will be the largest deregulatory action in American history, and it will save the American people $1.3 trillion in crushing regulations,” she said. The bulk of the savings will stem from reduced costs for new vehicles, with the EPA projecting average per vehicle savings of more than $2,400 for popular light-duty cars, SUVs and trucks, Leavitt said.

The endangerment finding is the legal underpinning of nearly all climate regulations under the Clean Air Act for motor vehicles, power plants and other pollution sources that are heating the planet. It is used to justify regulations, such as auto emissions standards, intended to protect against threats made increasingly severe by climate change — deadly floods, extreme heat waves, catastrophic wildfires and other natural disasters in the United States and around the world.

Legal challenges certain to come

Legal challenges are certain for any action that effectively would repeal those regulations, with environmental groups describing the shift as the single biggest attack in U.S. history on federal efforts to address climate change.

“The Trump administration is abandoning its core responsibility to keep us safe from extreme weather and accelerating climate change,’’ said Abigail Dillen, president of the nonprofit law firm Earthjustice. “There is no way to reconcile EPA’s decision with the law, the science and the reality of disasters that are hitting us harder every year. Earthjustice and our partners will see the Trump administration in court.”

EPA press secretary Brigit Hirsch said the Obama-era rule was “one of the most damaging decisions in modern history” and said EPA “is actively working to deliver a historic action for the American people.”

Trump, who has called climate change a “hoax,” previously issued an executive order that directed EPA to submit a report on “the legality and continuing applicability” of the endangerment finding. Conservatives and some congressional Republicans have long sought to undo what they consider overly restrictive and economically damaging rules to limit greenhouse gases that cause global warming.

Zeldin, a former Republican congressman who was tapped by Trump to lead EPA last year, has criticized his predecessors in Democratic administrations, saying they were “willing to bankrupt the country” in an effort to combat climate change.

Democrats “created this endangerment finding and then they are able to put all these regulations on vehicles, on airplanes, on stationary sources, to basically regulate out of existence … segments of our economy,” Zeldin said in announcing the proposed rule last July. ”And it cost Americans a lot of money.”

Peter Zalzal, a lawyer and associate vice president of the Environmental Defense Fund, countered that the EPA will be encouraging more climate pollution, higher health insurance and fuel costs and thousands of avoidable premature deaths. The EPA is focusing solely on industry costs while ignoring the rule’s climate and health benefits, he and other advocates said.

Zeldin’s push “is cynical and deeply damaging, given the mountain of scientific evidence supporting the finding, the devastating climate harms Americans are experiencing right now and EPA’s clear obligation to protect Americans’ health and welfare,” Zalzal said.

Supreme Court has upheld endangerment finding

The Supreme Court ruled in a 2007 case that planet-warming greenhouse gases, caused by burning of oil and other fossil fuels, are air pollutants under the Clean Air Act.

Since the high court’s decision, in a case known as Massachusetts v. EPAcourts have uniformly rejected legal challenges to the endangerment finding, including a 2023 decision by the U.S. Court of Appeals for the District of Columbia Circuit.

Following Zeldin’s proposal to repeal the rule, the National Academies of Sciences, Engineering and Medicine reassessed the science underpinning the 2009 finding and concluded it was “accurate, has stood the test of time, and is now reinforced by even stronger evidence.”

Much of the understanding of climate change that was uncertain or tentative in 2009 is now resolved, the NAS panel of scientists said in a September report. “The evidence for current and future harm to human health and welfare created by human-caused greenhouse gases is beyond scientific dispute,” the panel said.

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___ Associated Press writers Seung Min Kim in Washington and Bill Barrow in Atlanta contributed to this report.