Navajo Generating Station, near Page, Arizona. Photo: Jeffrey St. Clair.
In 2009, the U.S. Environmental Protection Agency formally declared that greenhouse gas emissions, including from vehicles and fossil fuel power plants, endanger public health and welfare. The decision, known as the endangerment finding, was based on years of evidence, and it has underpinned EPA actions on climate change ever since.
The Trump administration now wants to tear up that finding as it tries to roll back climate regulations on everything from vehicles to industries.
But the move might not be as simple as the administration hopes.
EPA Administrator Lee Zeldin sent a proposed rule to the White House Office of Management and Budget in early January 2026 to rescind the endangerment finding. Now, a Washington Post report suggests, action on it may be delayed over concerns that the move wouldn’t withstand legal challenges.
Cracks in the administration’s plan are already evident. On Jan. 30, a federal judge ruled that the Department of Energy violated the law when it handpicked five researchers to write the climate science review that the EPA is using to defend its plan. The ruling doesn’t necessarily stop the EPA, but it raises questions.
There’s no question that if the EPA does rescind the endangerment finding that the move would be challenged in court. The world just lived through the three hottest years on record, evidence of worsening climate change is stronger now than ever before, and people across the U.S. are increasingly experiencing the harm firsthand.
Several legal issues have the potential to stop the EPA’s effort. They include emails submitted in a court case that suggest political appointees sought to direct the scientific review.
To understand how we got here, it helps to look at history for some context.
The Supreme Court started it
The endangerment finding stemmed from a 2007 U.S. Supreme Court ruling in Massachusetts v. EPA.
The court found that various greenhouse gases, including carbon dioxide, were “pollutants covered by the Clean Air Act,” and it gave the EPA an explicit set of instructions.
The court wrote that the “EPA must determine whether or not emissions from new motor vehicles cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare.”
But the Supreme Court did not order the EPA to regulate greenhouse gas emissions. Only if the EPA found that emissions were harmful would the agency be required, by law, “to establish national ambient air quality standards for certain common and widespread pollutants based on the latest science” – meaning greenhouse gases.
The EPA was required to follow formal procedures – including reviewing the scientific research, assessing the risks and taking public comment – and then determine whether the observed and projected harms were sufficient to justify publishing an “endangerment finding.”
That process took two years. EPA Administrator Lisa Jackson announced on Dec. 7, 2009, that the then-current and projected concentrations of six key greenhouse gases in the atmosphere – carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride – threatened the public health and welfare of current and future generations.
Challenges to the finding erupted immediately.
Jackson denied 10 petitions received in 2009-2010 that called on the administration to reconsider the finding.
On June 26, 2012, the U.S. Court of Appeals for the D.C. Circuit upheld the endangerment finding and regulations that the EPA had issued under the Clean Air Act for passenger vehicles and permitting procedures for stationary sources, such as power plants.
This latest challenge is different.
It came directly from the Trump administration without going through normal channels. It was, though, entirely consistent with both the conservative Heritage Foundation’s Project 2025 plan for the Trump administration and President Donald Trump’s dismissive perspective on climate risk.
Trump’s burden of proof
To legally reverse the 2009 finding, the agency must go through the same evaluation process as before. According to conditions outlined in the Clean Air Act, the reversal of the 2009 finding must be justified by a thorough and complete review of the current science and not just be political posturing.
That’s a tough task.
Energy Secretary Chris Wright has talked publicly about how he handpicked the five researchers who wrote the scientific research review. A judge has now found that the effort violated the 1972 Federal Advisory Committee Act, which requires that agency-chosen panels providing policy advice to the government conduct their work in public.
All five members of the committee had been outspoken critics of mainstream climate science. Their report, released in summer 2025, was widely criticized for inaccuracies in what they referenced and its failure to represent the current science.
Scientific research available today clearly shows that greenhouse gas emissions harm public health and welfare. Importantly, evidence collected since 2009 is even stronger now than it was when the first endangerment finding was written, approved and implemented.
Berkeley Earth, CC BY-NC
For example, a 2025 review by the National Academies of Sciences, Engineering and Medicine determined that the evidence supporting the endangerment finding is even stronger today than it was in 2009. A 2019 peer-reviewed assessment of the evidence related to greenhouse gas emissions’ role in climate change came to the same conclusion.
The Sixth Assessment of the Intergovernmental Panel on Climate Change, a report produced by hundreds of scientists from around the world, found in 2023 that “adverse impacts of human-caused climate change will continue to intensify.”
Fifth National Climate Assessment
In other words, greenhouse gas emissions were causing harm in 2009, and the harm is worse now and will be even worse in the future without steps to reduce emissions.
In public comments on the Department of Energy’s problematic 2025 review, a group of climate experts from around the world reached the same conclusion, adding that the Department of Energy’s Climate Working Group review “fails to adequately represent this reality.”
What happens if EPA does drop the endangerment finding
As an economist who has studied the effects of climate change for over 40 years, I am concerned that the EPA rescinding the endangerment finding on the basis of faulty scientific assessment would lead to faster efforts to roll back U.S. climate regulations meant to slow climate change.
It would also give the administration cover for further actions that would defund more science programs, stop the collection of valuable data, freeze hiring and discourage a generation of emerging science talent.
Cases typically take years to wind through the courts. Unless a judge issued an injunction, I would expect to see a continuing retreat from efforts to reduce climate change while the court process plays out.
I see no scenario in which a legal challenge doesn’t end up before the Supreme Court. I would hope that both the enormous amount of scientific evidence and the words in the preamble of the U.S. Constitution would have some significant sway in the court’s considerations. It starts, “We the People of the United States, in Order to form a more perfect Union,” and includes in its list of principles, “promote the general Welfare.”
This article is republished from The Conversation under a Creative Commons license. Read the original article.