WASHINGTON • The Trump administration on Thursday announced the repeal of an Obama-era finding that greenhouse gas emissions endanger human health and eliminated federal tailpipe emissions standards for cars and trucks.

It is the most sweeping climate related policy rollback by the administration to date.

“Under the process just completed by the EPA, 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,” President Donald Trump said, calling it the biggest deregulatory action in U.S. history.

Trump announced the repeal beside EPA Administrator Lee Zeldin and White House Budget director Russ Vought, who has long sought to revoke the finding.

In a memo, the White House said the 2009 finding was used to “justify trillions of dollars in regulations” that included the push for electric vehicle mandates. Its repeal would give Americans regulatory relief and deliver more than $1.3 trillion in savings.

In Colorado, Democrats criticized the move. Gov. Jared Polis argued the “science is clear that pollution from cars and trucks harms our air quality and puts families – especially kids, seniors, and those with health conditions – at greater risk.” Attorney General Phil Weiser, who is running for governor, called it “misguided.”

On X, former President Barack Obama blasted the repeal, saying without the endangerment finding, “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.”

Meanwhile, U.S. Department of Energy Chris Wright, who is from Colorado, said the repeal means America is “returning to free and open dialogue around climate and energy policy – driving the focus back to following the data.”

Zeldin said the Trump administration took on the most consequential climate policy of the last 15 years.

“Referred to by some as the holy grail of federal regulatory overreach, the 2009 Obama EPA endangerment finding is now eliminated,” he said.

The endangerment finding was first adopted by the United States in 2009, and led the EPA to take action under the Clean Air Act of 1963 to curb emissions of carbon dioxide, methane, and four other heat-trapping air pollutants from vehicles, power plants and other industries.    

It came about after the Supreme Court ruled in 2007 in Massachusetts vs. EPA that the agency has authority to regulate carbon dioxide and other greenhouse gas emissions under the Clean Air Act.

Its repeal would remove the regulatory requirements to measure, report, certify, and comply with federal greenhouse gas emission standards for cars, but may not initially apply to stationary sources, such as power plants.

The transportation and power sectors are each responsible for around a quarter of U.S. greenhouse gas output, according to EPA figures.

The EPA said the repeal and end of vehicle emission standards will save U.S. taxpayers $1.3 trillion, while the Biden administration said the rules would have net benefits to consumers through lower fuel costs and other savings.

The Alliance for Automotive Innovation, representing major automakers, did not endorse the action but said “automotive emissions regulations finalized in the previous administration are extremely challenging for automakers to achieve given the current marketplace demand for EVs.”

Under former President Joe Biden, the EPA aimed to cut passenger vehicle fleetwide tailpipe emissions by nearly 50% by 2032 compared with 2027 projected levels and forecast between 35% and 56% of new vehicles sold between 2030 and 2032 would need to be electric.

The agency then estimated that the rules would result in net benefits of $99 billion annually through 2055, including $46 billion in reduced fuel costs, and $16 billion in reduced maintenance and repair costs for drivers.

Zeldin said the repeal would save Americans $2,400 on a new vehicle.

While many industry groups back the repeal of stringent vehicle emission standards, others have been reluctant to show public support for rescinding the endangerment finding because of the legal and regulatory uncertainty it could unleash.

Legal experts said the policy reversal could, for example, lead to a surge in lawsuits known as “public nuisance” actions, which had been blocked following a 2011 Supreme Court ruling that GHG regulation should be left to the Environmental Protection Agency instead of the courts.

In Colorado, environmental groups urged policymakers to “stand up to the Trump administration.”

“We needn’t look beyond our state’s own borders to see that the climate crisis is here and it’s dangerous. We experienced historic wildfires, continued power shutoffs during wind events, severe drought and warm temperatures,” Margaret Kran-Annexstein, the director of the Colorado Sierra Club, said in a news release. “Despite the Trump administration’s clear disdain for human life, there is no amount of climate denial that can stop people from building the more just and sustainable future they want.” 

Others, including the Natural Resources Defense Council and Earthjustice, have said they will challenge the reversal in court, setting off what could be a years-long legal battle up to the Supreme Court.

In its memo, the White House insisted that a policy decision of such magnitude as the 2009 finding, given its “sweeping economic and policy consequences,” lies with Congress alone.

The White House also argued that many predictions and assumptions justifying the rule did not materialize and that, using the same modeling by the previous administrations and their allies, “there would be no material impact on global climate indicators through 2100” even if the U.S. eliminated all of its greenhouse gas emissions from vehicles.

The coal industry celebrated the announcement, saying it would help stave off retirements of aging coal-fired power plants.

“Utilities have announced plans to retire more than 55,000 megawatts of coal-fired generation over the next five years. Reversing these retirement decisions could help offset the need to build new, more expensive electricity sources and prevent the loss of reliability attributes, such as fuel security, that the coal fleet provides,” said America’s Power President and CEO Michelle Bloodworth.

The Trump administration’s energy agency earlier ordered one of three generating units at a Colorado power plant to remain available for operation amid an impending shutdown of the station and its supplying coal mines.

Gazette reporter Scott Weiser contributed to this article.