Seizing a new opportunity they believe has been opened up by the White House, hard-line foes of climate action on Monday once again asked the Trump Administration to reverse the landmark Obama-era finding that greenhouse gases are a danger to human health and the environment.

The Competitive Enterprise Institute (CEI), a conservative Washington, D.C., think tank and steadfast ally of the fossil fuel industry, filed a petition with the U.S. Environmental Protection Agency (EPA), seeking to block the agency from continuing to use the so-called "endangerment finding" adopted by the agency in 2009 as a basis for policymaking.

The endangerment finding served as the foundation for most of President Barack Obama's climate agenda, providing the legal basis for his administration's actions to curb emissions from power plants and motor vehicles. The U.S. Supreme Court had ruled in 2007 that the EPA had authority to regulate greenhouse gases as pollutants if it found that they were a danger to human health and the environment.

If the EPA were to suspend the endangerment finding, it would have profound consequences for rules the agency adopted under the Clean Air Act.

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CEI has long challenged the science of climate change, and soon after President Donald Trump took office, the organization filed a petition with EPA challenging the endangerment finding on its scientific merits.

But CEI's new challenge is different—it doesn't attack the science per se, but instead challenges the process that the EPA used to adopt the endangerment finding. CEI argues that the scientific peer review done at that time did not meet the government's legal data quality requirements under guidelines expanded on April 24 by Trump's Office of Management and Budget.

"So you can believe in global warming, all the things that the IPCC [Intergovernmental Panel on Climate Change] says, and still agree with us that the peer review process was improper," said Devin Watkins, a CEI lawyer.

The EPA did not immediately respond to a request for comment on the petition.

How Trump's OMB Changed the Rules

The Trump administration's new guidance made at least two changes that have improved the prospects for such a process challenge, Watkins said.

First, it requires that OMB review EPA's response to the petition, giving the White House oversight over the process. And second, it sets a deadline of 120 days for the EPA to respond to such a petition. (In contrast, the agency faces no such deadlines for other most regulatory petitions, including CEI's previous endangerment finding challenge.)

The Trump administration has been rolling back Obama-era climate regulations, even with the endangerment finding still in place. But supporters of Trump's deregulatory agenda have been divided between pragmatists, who argue the administration should simply focus on the nuts and bolts of undoing regulations without wading into a battle over the science of climate change, and hard-liners who believe that rescinding the endangerment finding will be necessary to fend off climate policies for the long term.

"There will be future administrations dealing with these issues for years to come," Watkins said.

The petition details a number of ways in which it says that the EPA's peer review was deficient—including that it did not allow the public to nominate peer reviewers, and that some of the peer reviewers were federal scientists who were the very authors of the science that the agency relied upon for the endangerment finding. CEI also challenged the EPA's reliance on the IPCC's scientific assessments, arguing among other things that the IPCC's peer review process does not match the requirements that OMB had established for U.S. federal government data quality.

Science Supports 2009 Endangerment Finding

If anything, the scientific consensus on the causes and risks of global climate change have only become more robust in the ensuing decade, with several reports by the IPCC and federal agencies reaffirming it more strongly than ever. These assessments have received extensive peer review, and are endorsed as sound by the world's scientific academies.

"CEI has been on the record for years now, wanting the endangerment finding to be removed, and in that intervening time, the only thing that's happened is that the science of climate change has become ever clearer and ever more urgent," said Rachel Cleetus, policy director for the Union of Concerned Scientists.

Pointing to the IPCC's report last fall on the risks of the planet warming beyond 1.5 degrees Celsius and to the U.S. National Climate Assessment, she said, "Everything that was in the endangerment finding is now highlighted and in bold face in the latest science."

The endangerment finding faced multiple challenges when it was first adopted, but in 2012 it was upheld by the U.S. Court of Appeals for the District of Columbia Circuit.

Cleetus said she remains confident that the endangerment finding will survive any challenge, but the legal wrangling itself is consequential, because the government is caught in a debate over the validity of the science instead of working on solutions.

"They know they are going to ultimately lose because the science is clear, but they are seeking to delay and obfuscate," Cleetus said. "The tactic is clear, they're trying to buy time for the fossil fuel industry to extract the last bit of profit it can."