EPA’s proposed repeal of the nation’s climate rule for power plants may reveal how the agency plans to undo the scientific basis for regulating greenhouse gases, known as the endangerment finding.
It could hinge on a single word: “Significantly.”
Three EPA administrations — including President Donald Trump’s first — have used Section 111 of the Clean Air Act to curb climate pollution in the power sector. The provision’s language asks EPA to determine whether a new stationary source “causes, or contributes significantly” to harmful air pollution.
Conservative legal experts — including some who worked in past Republican administrations — told POLITICO’s E&E News that EPA could reinterpret “significantly” to play down the role that carbon emissions from U.S. power plants and other domestic sectors have on global warming.
If successful, the argument could be used to undermine the endangerment finding — and the authority it granted to EPA to regulate six greenhouse gases. It would also allow the Trump administration to wage war on a single word — and how it has been used by Democratic administrations — rather than on the trove of scientific studies that offer evidence of the perils that climate change poses to people.
“These kinds of more finessed approaches are certainly smarter than taking on the endangerment finding head on,” said Jonathan Adler, a law professor at Case Western Reserve University School of Law. “Targeting specific rules is better than trying to tackle all of climate science.”
The White House regulatory office is reviewing a draft rule that would be used to scrap the power plant climate regulations that were finalized last year. The draft was submitted for review in record time — a mere 102 days after Trump’s second inauguration — and is widely believed to exclude a replacement rule for coal and gas plant emissions — a move that would leave the power sector unregulated for climate pollution.
The word “significantly” doesn’t show up in other Clean Air Act sections that govern how EPA weighs the dangers of pollution for the purposes of regulation. For example, the original Obama-era endangerment finding was drafted under Section 202 (a), which directs EPA to regulate pollutants from new motor vehicles if they “cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.”
Under that section, any level of harmful pollution triggers an endangerment finding, which in turn opens the door for regulation. EPA would likely aim to undo that broader finding, too, at a later date.
But the presence of “significantly” in Section 111 gives EPA more wiggle room. Other language does too, including phrases in the same section that give EPA Administrator Lee Zeldin the task of deciding what “significantly” means.
“‘Contribute significantly’ is not defined in the statute,” said Jeff Holmstead, who served as EPA air chief under President George W. Bush. “It’s the sort of term that the administrator has some discretion on.”
Zeldin is likely to define “significantly” differently from past EPA leaders, such as Gina McCarthy or Michael Regan, both of whom led the agency under Democratic presidents. Adler said EPA would have to account for that change in the rule.
“They will have to defend that change, and they will have to hope that their interpretation of ‘significantly’ is more convincing to the courts than the prior definition,” said Adler.
Future administrations could reverse any changes that Zeldin makes to the interpretation of “significantly.”
Future administrations could reverse any changes that Zeldin makes to the interpretation of “significantly.”
An agency spokesperson declined to provide details about its plans, saying only that the agency “will be kicking off a formal reconsideration of the 2009 Endangerment Finding in collaboration with the Office of Management and Budget and other relevant agencies.”
Attacking a word, not science
The administration’s efforts to repeal the power plant rule — and the endangerment finding — are coming as the power sector’s contribution to climate change has fallen.
EPA’s most recent greenhouse gas inventory, which the Environmental Defense Fund, an advocacy group, released this month after obtaining it through a Freedom of Information Act request, showed that in 2023 the power sector contributed 31 percent of U.S. carbon emissions from fossil fuel combustion.
But that share is trending down.
The power sector released 22.3 percent less carbon from fossil fuels in 2023 than it did in 1990, driven mostly by a transition away from coal-fired electricity. Transportation overtook power generation as the highest-emitting U.S. sector in 2016, and its lead has grown ever since.
The U.S. economy’s overall contribution to global CO2 emissions is also falling. In 2015, when the nation’s first climate rule for power plants, the Clean Power Plan, was finalized, the U.S. was responsible for 14.2 percent of the world’s CO2 emissions, according to Carbon Brief, a U.K. media outlet that covers climate change. In 2023, it was 13 percent.
So, EPA could argue that the U.S. power sector contributes less to the global problem of climate change than it did when the Obama administration first started using Section 111 of the Clean Air Act to regulate it.
“You don’t have to dig into the science, and you don’t need a huge record,” said Holmstead, who is an attorney with Bracewell LLP. “You know what power plant CO2 emissions are. We have great data on that. We know that as a percentage of global emissions, they’re continuing to fall.”
“I don’t think that’s a bad argument,” he said.
If EPA succeeds in defining power sector emissions as not “significant” to climate change, it could have a cascading effect. Other stationary source categories — like oil and gas facilities — could wiggle out of regulatory requirements created by the endangerment finding. Because they contribute smaller amounts of U.S. emissions than the power sector.
But EPA faces some obstacles to doing that. And at least one stems from Trump himself.
A week before Trump left office in January 2021, EPA published a final “significant contribution finding” in the Federal Register that attempted to define any sector that’s responsible for less than 3 percent of overall U.S. greenhouse gas emissions. The idea was to identify emissions sources that had contributed too little pollution to warrant regulation. The finding said stationary sources like oil and gas production, iron and steel manufacturing, and landfills all fell comfortably below that threshold.
“It was an effort to protect smaller, but still important source categories from regulation,” said Sean Donahue, an attorney with Donahue Goldberg & Herzog. “It was an effort to pre-exclude them.”
But the finding affirms that power plants meet every possible criteria for being significant contributors of greenhouse gas emissions.
“Although emissions from [power plants] have fallen since the EPA promulgated the 2015 rule, they still remain uniquely large among stationary source categories,” it stated.
The power sector’s contribution to climate pollution was “greater than the emissions of all but four countries,” it noted, making it “the most appropriate place” for EPA and states to look for opportunities to reduce emissions.
The U.S. Court of Appeals for the District of Columbia Circuit vacated the administration’s last-minute finding on procedural grounds. But it could still present a stumbling block for EPA, if it offers a radically different conclusion, said Donahue.
He said such an approach would be “indefensible.”
“Anyone who knows anything about climate change knows that it is inherently produced by multiple sources around the world, and that the only way you mitigate is by attacking at least the largest of those source categories,” Donahue said.
If EPA were to say power sector emissions aren’t significant enough to warrant regulation, he said, “I think you’re basically saying nothing would be.”
