The Environmental Protection Agency on Thursday overturned its own 2009 finding that greenhouse gas emissions endanger human health, setting up a lengthy legal battle that could end up at the Supreme Court.
The agency’s “endangerment finding” underpinned federal climate regulations issued by the Obama and Biden administrations, including limits on carbon emissions from cars, trucks, and power plants. By reversing it, the Trump administration is attempting to block the federal government — including future administrations — from curbing emissions at all.
If the inevitable lawsuits over the EPA’s decision reach the Supreme Court, its conservative majority could chip away at, or even overturn altogether, a prior landmark 2007 ruling that paved the way for the agency to regulate emissions. In Massachusetts v. EPA, the court ruled that carbon dioxide and other greenhouse gases are considered “air pollutants” and directed EPA to assess their impact on human welfare — allowing the agency to regulate them. That led to the endangerment finding two years later.
EPA administrator Lee Zeldin on Thursday said a policy with such “sweeping economic” consequences should be passed by Congress. The agency in a separate rule on Thursday repealed tailpipe pollution limits for cars and trucks, which had been in place since 2012 and helped usher in more gas-efficient and electric vehicles.
The implications for the power sector are more diffuse. Despite attempts by the Obama and Biden administrations to limit emissions from power plants, rules never took effect. However, many utilities have had to comply with state-level renewable energy goals.
By ending the finding, EPA ignored the overwhelming scientific evidence that climate change is harming human health. The vast majority of scientists agree that emissions — mainly from burning fossil fuels — are causing global temperatures to rise and fueling more frequent and destructive hurricanes, wildfires, and other storms. A warmer climate is also contributing to higher cases of human diseases like West Nile and Dengue fever because the insects that carry them are expanding their geographic range.
Both California Gov. Gavin Newsom and the Natural Resources Defense Council on Thursday said they will challenge the EPA’s decision. NRDC President and CEO Manish Bapna said the Trump administration is trying to rehash legal arguments SCOTUS has already resolved.
“With millions of Americans facing stronger storms, hotter heat waves and more dangerous wildfires, the Trump administration is trying to pretend it’s all a hoax, and there’s nothing to be done about it,” Bapna said. “But the impacts of climate change are right here, right now.”
Energy transition still underway
As these legal battles play out, analysts suggest that the energy transition will continue no matter how they are resolved — just at a slower pace. U.S. emissions have generally fallen since 2005, as the power sector switched from coal to cheaper, less-emitting natural gas. Meanwhile, installations of solar, wind, and battery storage have continued to rise every year as costs drop.
Even before EPA rolled back the endangerment finding, the U.S. was already expected to slash emissions at a much slower pace because Congress ended tax breaks for renewable energy and EVs in the GOP’s One Big Beautiful Bill, as well as a methane tax.
The Rhodium Group in January projected a “substantial slowdown” in emissions reductions by 2035, compared to an outlook it published in 2024. The group expects U.S. emissions to decline by 26-35% by 2035 (compared to 2005 levels), as opposed to 38-56%.
Last year, U.S. emissions rose by 2.4% after two straight years of decline, driven in part by a surge in coal power. Utilities chose to burn more coal to meet power demand last year because it was cheaper than gas, which saw a 58% price spike due to rising LNG exports and cold snaps. Meanwhile, transportation emissions were essentially flat due to the adoption of hybrid and electric vehicles. But sales of cleaner cars slowed at the end of 2025, after Congress repealed tax credits in the OBBB.
Still, John Tobin-de la Puente, a professor at Cornell University’s SC Johnson College of Business, said he doesn’t expect companies to make long-term plans based on the Trump administration’s actions today. Businesses operate on a longer time scale than four-year U.S. presidential election cycles, he said, and there’s a good chance that a future administration will regulate carbon emissions.
