On Thursday, the Trump administration will rescind the central scientific finding that underpins much of the nation's climate pollution rules, its most aggressive action yet to halt initiatives that address planetary warming.
The 2009 Environmental Protection Agency endangerment finding was a determination that pollutants from developing and burning fossil fuels, such as methane and carbon dioxide, can be regulated under the Clean Air Act. The EPA now argues that the Clean Air Act does not give it the legal authority to regulate greenhouse gases.
"This will be the largest deregulatory action in American history," White House Press Secretary Karoline Leavitt said at a Tuesday briefing. EPA Administrator Lee Zeldin is expected to join President Trump at the White House to formalize the decision on Thursday, Leavitt said.
The endangerment finding stemmed from a section of the Clean Air Act focused on regulating vehicle emissions. So, the EPA is expected to also end rules to reduce climate pollution from cars and trucks. Transportation is the largest source of direct greenhouse gas emissions in the United States.
"This is a slap in the face to the millions of Americans who are living through climate disasters and their aftermath," says Abigail Dillen, president of Earthjustice, a nonprofit environmental law group. "And we will see this administration in court, to ensure that our government does its job to protect us."
The administration's decision comes in the wake of the three hottest years humans have ever recorded, deadly flooding in communities across the U.S. from Texas to Alaska and climate-fueled wildfires that destroyed thousands of homes in Los Angeles.
Trump has rejected the basic tenets of climate science and called climate change a "con job." This is his latest effort to reverse former President Biden's ambitious climate agenda and make it more difficult for future administrations to limit the human-caused greenhouse gas pollution heating the planet. And it's almost certain to lead to years of court battles that will end up before the U.S. Supreme Court.
Ending a cornerstone of U.S. climate action
In 2007, the Supreme Court found in Massachusetts v. EPA that the agency is required to regulate carbon dioxide and other greenhouse gas emissions under the Clean Air Act. Then in 2009 the EPA, during the Obama administration, declared that greenhouse gases in the atmosphere were a hazard to people.
The endangerment finding is the basis for rules regulating climate pollution from coal and gas-fired power plants, car and truck exhaust, and methane from the oil and gas industry.
On the first day of his second term, Trump signed an executive order asking the EPA administrator to submit recommendations "on the legality and continuing applicability" of the endangerment finding. That echoes recommendations laid out in the Heritage Foundation's Project 2025, a sweeping conservative plan to remake American society that includes limiting regulation of climate pollution.
Zeldin first announced the EPA's intention to eliminate the endangerment finding last March.
"We are driving a dagger straight into the heart of the climate change religion to drive down cost of living for American families, unleash American energy, bring auto jobs back to the U.S. and more," Zeldin said in a news release at the time.
While EPA regulations are typically rooted in science, Trump's EPA has taken more of a legal approach to overturning the endangerment finding. And the science the agency did depend on for its proposed rule came from the Department of Energy's controversial Climate Working Group (CWG). The group wrote a report that prompted dozens of independent scientists to issue a joint rebuttal saying it was full of errors. The panel has since been disbanded, and a federal judge ruled that the Energy Department violated public records laws when it created the group.
What this means for cars
The EPA's limits on greenhouse gas emissions from cars and trucks have been central to the agency's years-long push to make the U.S. auto industry sell less-polluting vehicles. Under the Biden administration, the standards became more ambitious than ever, setting limits so low that in order to meet them, the White House expected automakers would make electric vehicles up to 56% of their sales by 2032.
The Trump administration is now poised to entirely eliminate those restrictions. That's part of a multi-pronged rollback of policies meant to support EVs. The administration has also blocked California's longstanding ability to set its own vehicle rules and made federal fuel economy rules less stringent. Meanwhile, Congress has eliminated penalties for noncompliance with those fuel economy rules, essentially giving automakers free rein to focus on large, less-efficient gas and diesel vehicles. Because big, gas-guzzling trucks are very profitable, that's been a boost to automakers' bottom lines, partially offsetting the higher costs from tariffs.
The Trump administration and Congress have also eliminated a consumer tax credit for electric vehicles, and delayed, blocked and redirected federal money that was meant to support the buildout of electric vehicle charging stations.
The EPA's greenhouse gas limits for cars benefited all-electric automakers like Tesla and Rivian, but traditional automakers argued that the Biden-era rules were out of step with market realities. Even with the consumer tax credit and other incentives, EVs made up around 10% of new car sales in 2024, and growth of EVs had flagged as mainstream buyers were slow to embrace them. Sales were nowhere near on track to hit the EPA's targets.
As a result, the auto industry was broadly enthusiastic about plans to weaken EV regulations. However, constant regulatory whipsawing creates a headache for them when it comes to product planning, which needs to be done years in advance. Automakers are also watching with increasing anxiety as Chinese automakers release more impressive and more affordable EVs every year. Executives say that they need to invest in EVs to be competitive long-term. MEMA, the trade group representing the manufacturers who supply parts to automakers, asked the EPA to keep greenhouse gas rules in place, to provide stability that would help U.S. companies stay competitive in the global EV race."
Meanwhile, some industry members have warned that eliminating the endangerment finding, rather than just imposing a weaker set of greenhouse gas standards for cars, could trigger a legal battle with an uncertain outcome, and open the door to state-by-state rules, if there's no overarching federal regulation.
On Thursday, Leavitt said that the rescission of the endangerment finding would save $1.3 trillion, mostly from the money car buyers would save on the sticker price of new vehicles. Electric vehicles do typically cost more up front in the U.S., but are generally cheaper to operate over their lifespan. In fact, economic analyses have found that under the more stringent EPA rules, drivers save overall because they use less gasoline — and that's before considering health and environmental benefits.
Years of legal battles ahead
The U.S. is the largest historical emitter of man-made climate pollution and, under the 2015 Paris climate agreement, agreed to contribute to the global effort to reduce emissions and limit warming. Trump has withdrawn the U.S. from that agreement and a 1992 treaty that underlies it.
To challenge the legal foundations of the endangerment finding, the Trump administration argued that the EPA, under then-President Barack Obama, established the endangerment finding in "a flawed and unorthodox way" and "did not stick to the letter of the Clean Air Act." The Trump EPA now argues that previous administrators overstepped their legal authority and "imposed trillions of dollars of costs on Americans."
Environmental groups argue that the law is clear, and point to the section of the act that requires the EPA administrator to regulate, "air pollution which may reasonably be anticipated to endanger public health or welfare."
Environmentalists also say Trump's EPA is ignoring the costs of damage from extreme weather fueled by climate change when it estimates that eliminating regulations based on the endangerment finding will save trillions. And they argue the science about the risks of climate change were clear in 2009, when the endangerment finding was issued — and are even more clear now.
"The Trump administration is trying to upend very well settled law, about what our Clean Air Act not only allows but requires our government to do, to protect us from climate change," Dillen says.
Once the EPA publishes the final decision on the endangerment finding in the Federal Register, there likely will be years of legal battles ahead that could end up before the Supreme Court.
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