WATCH: Trump and EPA’s Zeldin announce end to scientific basis for US action on climate change

WASHINGTON (AP) — The Trump administration on Thursday rescinded a scientific discovery that has long been the central basis of U.S. work to regulate greenhouse gas emissions and fight climate change, the most aggressive move by a president to roll back climate regulations.

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The EPA rule rescinds a 2009 government declaration known as a hazard finding that determined that carbon dioxide and other greenhouse gases endanger public health and welfare.

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The Obama administration’s finding of danger is the legal basis for nearly all climate regulations under the Clean Air Act for cars, power plants and other sources of pollution that heat the planet.

Experts say legal challenges are certain for the measure that repeals all greenhouse gas emissions standards for cars and trucks, and could unleash a broader rollback of climate regulations related to stationary sources such as power plants and oil and gas facilities. Ann Carlson, a professor of environmental law at UCLA School of Law, said overturning the result “would wreak more havoc” than other actions the Trump administration has taken to roll back environmental rules.

EPA Administrator Lee Zeldin, who has steered the agency toward a business-friendly approach that has repeatedly reversed climate regulations, said repealing the hazard finding “would be the largest deregulatory action in American history.”

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Environmental groups called the move the largest single attack in US history against federal authority to address climate change.

Zeldin announced the completion of the base on Thursday alongside President Donald Trump. The EPA also said it would propose a two-year postponement of a Biden-era rule restricting greenhouse gas emissions from cars and light trucks.

Zeldin, a former Republican congressman appointed by Trump to lead the EPA last year, criticized his predecessors in Democratic administrations, saying that in the name of tackling climate change, they were “willing to bankrupt the country.”

Myron Ebell, a conservative activist who has questioned the science behind climate change, said withdrawing the danger finding “is the most important step the Trump administration has taken yet to return to energy and economic rationality.” He added that the decision “will make our economy more productive and benefit consumers, immediately by allowing auto manufacturers to produce vehicles that people want to buy.”

The Supreme Court upheld the risk finding

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

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

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The hazard finding is widely considered the legal basis underpinning a series of regulations aimed at protecting against increasingly serious threats due to climate change. This includes deadly floods, extreme heat waves, catastrophic wildfires, and other natural disasters in the United States and around the world.

Gina McCarthy, a former administrator of the Environmental Protection Agency who served as a White House climate adviser in the Biden administration, called the Trump administration’s actions reckless. “This EPA would rather spend its time in court working for the fossil fuel industry than protecting us from pollution and the escalating effects of climate change,” she said.

The EPA has a clear scientific and legal obligation to regulate greenhouse gases, McCarthy said, adding that the evidence supporting the danger finding has “become stronger” as the health and environmental risks of climate change have become impossible to ignore.

David Doniger, a climate expert at the Natural Resources Defense Council, said Trump and Zeldin are trying to use overturning the result as a “killing bullet” that would allow the administration to render nearly all climate regulations invalid. A repeal could erase existing restrictions on greenhouse gas pollution from cars, factories, power plants and other sources and could prevent future administrations from proposing rules to address global warming.

The EPA’s action follows an executive order from Trump directing the agency to report on the “legality and continuity of application” of the hazard finding. Conservatives and some Republicans in Congress have long sought to repeal what they view as overly restrictive and economically harmful rules to limit greenhouse gases that cause global warming.

Exhaust pipe emission limits have been targeted

Zeldin and Transport Minister Sean Duffy have moved to dramatically reduce limits on tailpipe emissions from cars and trucks. The rules imposed under Democratic President Joe Biden aim to encourage American automakers to build and sell more electric cars. The transportation sector is the largest source of greenhouse gas emissions in the United States

The Trump administration in December announced a proposal to weaken the auto industry’s mileage rules, easing regulatory pressure on automakers to control pollution from gasoline-powered cars and trucks. The EPA said its two-year delay of a Biden-era rule on greenhouse gas emissions from cars and light trucks will give the agency time to develop a plan that better reflects the reality of slowing electric vehicle sales, while promoting consumer choice and lowering prices.

The mileage plan would significantly reduce rule-setting requirements on how far new vehicles need to travel on a gallon of gasoline. Trump said the rule change would lower new car prices and increase Americans’ access to the full range of gasoline vehicles they need and can afford.

Environmental groups said the plan would keep polluting, gas-burning cars and trucks on American roads for years to come, threatening the health of millions of Americans, especially children and the elderly.

Advocates say the Biden-era standards for clean cars and trucks are among the most important and effective protections to address climate pollution.