Can Trump Reverse the Climate Endangerment Finding?

 

Expert Blog

Can Trump Reverse the Climate Endangerment Finding?

 

Sixteen years ago, the EPA found that climate change is real, dangerous, and caused by carbon pollution. Trying to repeal that finding is a fool's errand.

 

August 14, 2025

David Doniger

Senior Attorney and Strategist, Climate & Energy

https://www.nrdc.org/bio/david-doniger/can-trump-reverse-climate-endangerment-finding

 

President Trump’s assault on the nation’s climate protection policies is going even further than he dared in his first term. Appearing last month at an Indianapolis truck dealership while hundreds of millions of Americans sweltered under July’s heat dome, U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin announced the Trump administration’s proposed repeal of the government’s foundational scientific finding that carbon dioxide, methane, and other climate-changing pollutants are dangerous to our health and well-being.

 

At the same time, Zeldin proposed to repeal every standard for those pollutants from cars, SUVs, vans, pickups, and big trucks going back to 2010. (For a deeper analysis on those rollbacks, read this blog.)

 

5 Facts About the Endangerment Finding

Issued by the EPA in 2009, the endangerment finding is the scientific and legal foundation for 16 years of Clean Air Act standards to cut climate pollution from cars and trucks. It also supports standards to cut climate pollution from power plants, oil and gas drilling, and other industries. The Trump EPA hopes to kill the car and truck standards now, and later, all the other standards by repealing that finding and allowing industries to freely spew climate-harming pollution again without limit.

 

It is stunning that the Trump team would even consider this in the middle of another scorching summer and on the heels of disasters like the Texas flooding that killed at least 135 people last month, the deadly fires in Los Angeles in January, and the catastrophic hurricane flooding in North Carolina last year.

 

Indeed, as you can see below, while Zeldin spoke, a Fox television chyron blared out warnings of a 126-degree heat index in nearby Missouri.

 

Yet Administrator Zeldin has gone all in for climate denial, calling his move “a dagger through the heart of the climate change religion” and “the most consequential day of deregulation in American history.”

 

This is bringing thrills to a small cadre of fringe climate science deniers. No one should be surprised. These deniers got their wishes into Project 2025 (page 425), which calls for “[e]stablish[ing] a system, with an appropriate deadline, to update the 2009 endangerment finding.” Indeed, Zeldin was joined in Indianapolis by U.S. Department of Energy (DOE) Secretary Chris Wright, who hired five of those climate deniers to gin up a paper that purports to refute the broad scientific consensus reflected in decades of reports by the Intergovernmental Panel on Climate Change (IPCC) and the National Climate Assessments.

 

The deniers’ joy, however, will be short-lived.

 

In the face of overwhelming science, it’s impossible to think that the EPA will be able to develop a contradictory finding that can stand up in court. Indeed, the courts have repeatedly rejected attacks on the endangerment finding. Even Trump’s first-term EPA administrators understood that trying to reverse it was “a fool’s errand,” in the words of one conservative former agency official.

 

Zeldin is abandoning the EPA’s primary mission to protect the health and welfare of the American people. In the Trump administration, the EPA’s mission is to make the world safe for unlimited exploitation of coal, oil, and gas.

 

They’re swinging for the fences. But when you swing for the fences, most of the time, you strike out.

 

Under the Clean Air Act, the EPA is legally required to limit vehicle emissions of any air pollutant that, as determined by the agency, “causes or contributes to air pollution that may reasonably be anticipated to endanger public health or welfare.” Public health plainly includes pollution-related deaths or illnesses. The law defines adverse effects on welfare to include any kind of environmental and economic harms beyond human health—the statutory definition specifically calls out harm to “weather” and “climate.”

 

In 2007, the U.S. Supreme Court held in Massachusetts v. EPA that carbon dioxide and other greenhouse gases are unambiguously air pollutants under the Clean Air Act. The Court also held that the EPA’s refusal to regulate them during the Bush administration was based on a hodgepodge of reasons it was not allowed to consider under the Clean Air Act, like whether voluntary action is enough or whether the United States should hold back acting because other countries supposedly haven’t done enough. The Court ordered the EPA to decide, up or down, based only on the science, whether greenhouse gases endanger health or welfare.

 

President George W. Bush initially said he’d abide by the ruling, and his EPA prepared a positive finding. But Bush’s Office of Budget and Management (OMB) refused to open the email containing the EPA finding.

 

So it fell to the Obama EPA, which, in 2009, determined that carbon dioxide, methane, and four other greenhouse gases do indeed endanger health and welfare and that vehicle emissions contribute to that harm. The EPA adopted these findings, relying on reports from the IPCC, the National Academy of Sciences, the multiagency National Climate Assessments, and hundreds of scientific papers and after receiving and reviewing thousands of public comments. The endangerment finding for vehicle emissions—and subsequent findings for other sources—triggered the EPA’s legal duty to set standards for cars, trucks, power plants, aircraft, and oil and gas operations.

 

When climate deniers, fossil fuel companies, and their red state allies challenged the EPA finding, the U.S. Court of Appeals for the D.C. Circuit upheld it, explaining that it was backed by an overwhelming scientific record and rejecting the deniers’ contrary arguments. The Supreme Court denied review.

 

The Supreme Court has followed the Massachusetts precedent in three other climate change cases decided over the following 15 years. While two of those decisions put limits on precisely what form EPA regulations can take, none of those decisions casts any shade on the underlying endangerment finding and the EPA’s legal duty to act on climate pollution. That’s true of even the most recent decision, West Virginia v. EPA, which upheld the EPA’s authority to set “traditional” technology-based standards for power plants’ climate pollution, even as it ruled out a particular emission credit and trading approach.

 

And as part of the 2022 Inflation Reduction Act (IRA), Congress amended the Clean Air Act to codify the Massachusetts holding that greenhouse gases are air pollutants, by adding Sections 135 and 136 to the law. (Even though Trump’s One Big Beautiful Bill Act rolled back many of the IRA’s clean energy grants and tax incentives, it did not reverse this definition of greenhouse gases as air pollutants.)

 

The endangerment finding holds up, but attacks keep coming

The scientific basis for the endangerment finding has only strengthened since 2009. A Denali-size mountain of evidence has grown to Mount Everest–size since then. While some may have thought in 2009 that the risks of climate change still lay in the distant future, by now the impacts are blindingly obvious to millions of ordinary Americans suffering through more severe and more frequent storms, droughts, wildfires, and other extreme weather events.

 

When issuing standards for vehicles, power plants, oil and gas, and aircraft during the Obama and Biden administrations, the EPA regularly updated the endangerment finding to reflect the ever more compelling science and to reiterate the agency’s legal obligation to act.

 

The climate denier cadre did not go away, however. In Trump’s first term, they petitioned the EPA to rescind the endangerment finding. Neither of Trump’s first-term EPA chiefs—Scott Pruitt and Andrew Wheeler—took the bait. When Biden's EPA denied the petitions, the D.C. Circuit turned away the challengers again—and again, the Supreme Court denied review.

 

Back in office for a second term, President Trump set out in the opposite direction. He issued a day one executive order, entitled “Unleashing American Energy” that set in motion his administration’s attempt to kill the endangerment finding. The order directed agencies to “implement action plans to suspend, revise, or rescind” all regulations that impose an “undue burden” on oil, gas, coal, and other Trump-favored energy resources. The targets include Clean Air Act standards for vehicles, power plants, and oil and gas, as well as other pollution and efficiency standards.

 

The order also told Zeldin to give OMB his “recommendation” on “the legality and continued applicability” of the endangerment finding. Zeldin sent his recommendations to proceed with repeal in February. As mentioned, Zelding unveiled the formal proposal in July, with a deadline for public comment by September 22.

 

Scientists and the public demand action

Now that the proposal is public, it is generating massive pushback from scientists and ordinary citizens across the country.

 

The original endangerment finding was based on thousands of scientific studies, including analyses by the National Academy of Sciences, the IPCC, and others. It has only gotten stronger.

 

The latest IPCC report, for example, says climate change is “widespread, rapid, and intensifying,” and there is “very high confidence” that the risks and adverse impacts of climate change will escalate without major emission reductions. That’s stronger than any prior conclusion.

 

The EPA repeal proposal, however, rejects the consensus findings of the IPCC, the National Academy of Sciences, and the National Climate Assessments. Instead, it relies on the report by the five climate deniers commissioned by DOE Secretary Wright, which purports to poke holes in those authoritative findings.

 

The DOE report has stirred outrage from dozens of climate scientists who contributed to the IPCC and other consensus reports. Indeed, the National Academy of Sciences has announced that it will prepare another report updating the science undergirding the endangerment finding and responding to the DOE paper.

 

It is difficult to imagine writing a rational decision, supported by a record, that refutes this mountain of evidence. They’ll get nowhere trying to dismiss the massive pollution from vehicles, power plants, and the oil and gas industry as insignificant. Anything like this will surely be struck down as arbitrary and capricious by the D.C. Circuit (the only lower court where the decision can be challenged).

 

Meanwhile, Zeldin’s EPA is throwing lots of other spaghetti at the wall. For example, while it concedes that the Supreme Court held that greenhouse gases are air pollutants under the Clean Air Act, the agency now contends that it only has authority over vehicle pollutants that cause “local or regional” harm, not those that contribute to global climate change. The EPA also argues that the law covers only pollutants that hurt you directly when you breathe them, not those that cause deadly heat waves, wildfires, floods, and storms. There are no such limitations in the Clean Air Act.

 

And the EPA is also proposing to find that there have never been any workable, affordable emission controls—even though today’s new cars emit half the carbon pollution of those made in 2009 and save their owners thousands of dollars in reduced fuel costs.

 

Plainly, the Trump EPA is swinging for the now more conservative Supreme Court to come to its rescue. The Court, however, would defy its long-standing rules of behavior if it were to revisit Massachusetts or its three subsequent climate decisions, especially now that Congress has expressly put its holding that greenhouse gases are air pollutants into the Clean Air Act. And the Court will likely think twice before further stretching its public credibility by contradicting the scientific consensus and announcing that climate change isn’t real.

 

But the Trump team has gone all in on outright climate denial. They have set off the EPA toward the edge of the cliff.

 

NRDC and our partners are preparing public comments objecting to the EPA’s proposed endangerment repeal. States and businesses will make their objections known as well. Comments are due September 22, and you can let the EPA know what you think by submitting your views here.

 

This is going to get ugly. We’ll fight them all the way, and we’ll see them in court.

 

This blog was originally published on January 23, 2025, and has been updated with new information and links.