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Scott Pruitt,Watch Chrysalis Online the administrator of the Environmental Protection Agency (EPA), signaled in testimony before the Senate Environment and Public Works Committee on Tuesday that he is open to revisiting a bedrock scientific analysis that paved the way for his agency to regulate planet-warming greenhouse gases. If he does so, it could take the EPA entirely out of the ballgame when it comes to limiting emissions of carbon dioxide, methane, and other global warming pollutants.

It would also set up an epic legal battle that could go on for years.

That Pruitt is willing to entertain the notion of revisiting what is known as an “endangerment finding” under the Clean Air Act tells you a lot about how Pruitt views his own agency. He has spent his first year as administrator as a kind of trojan administrator, bent on destroying the agency’s work from within. He has swiftly rolled back regulations on everything from pesticide use to methane emissions, all while downsizing the agency’s workforce to Reagan-era levels.

SEE ALSO: EPA administrator Scott Pruitt kept close tabs on scrubbing agency's climate websites, documents show

The 2009 endangerment finding holds that carbon dioxide and emissions of other greenhouse gases from mobile sources, such as cars and trucks, “threaten the public health and welfare of current and future generations.” It was based entirely on the peer reviewed scientific literature tying global warming to greenhouse gas emissions from human activities.

Here's why this is a big deal: If this analysis is overturned, it would get the EPA out of the business of regulating global warming altogether, which the agency has the authority to do based on a 2007 Supreme Court decision.

When he was first confirmed in February 2017, Pruitt said the endangerment finding, which took about 2 years for agency scientists to produce, was settled law.

Here is the transcript of an exchange Pruitt had with Massachusetts Democrat Ed Markey during his confirmation hearing on Jan. 18, 2017.

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Markey:Will you promise to keep on the books the scientific finding that carbon pollution poses a danger to the American public health and welfare?

Pruitt:Two things, Senator. First, with respect to Massachusetts v. EPA, the Supreme Court said to the EPA that they had to make a decision.

Markey:That’s right.

Pruitt:To determine whether CO2 posed a risk and, as you indicated, in 2009 they did so. That is the law of the land, those two cases. There is an obligation of the EPA Administrator to do his or her job in fulfilling Massachusetts v. EPA and that endangerment finding from 2009.

Markey:So you will keep that scientific finding on the books?

Pruitt:That the endangerment finding is there and needs to be enforced and respected. Senator Markey:You will not review that scientific finding? Pruitt:There is nothing that I know that would cause a review at this point.

On Tuesday, though, Pruitt sang a different tune. When asked by ranking member Tom Carper of Delaware whether he still favors leaving the endangerment finding alone.

"We have not made a decision or determination on that," Pruitt said, leaving the door wide open to reconsidering the finding.

Let's just be clear about this. If Trump's EPA reverses the endangerment finding, it would pull the rug out of any attempts to regulate carbon dioxide emissions using regulatory means. Only congressional action, or perhaps an extraordinary court ruling, could compel national policy making then.

In fact, one way Pruitt may be maneuvering to undermine the endangerment finding is by holding public debates on climate science, the so-called "red team, blue team" debates, that are widely assumed to be skewed toward industry interpretations of the science.

During Tuesday's hearing, Pruitt said the debates "are still under consideration" despite being denounced by scientific organizations and prominent climate scientists as a sham.

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Under former president Barack Obama, the EPA built upon the endangerment finding and crafted far-reaching regulations aimed at reducing emissions from coal-fired power plants, which is known as the Clean Power Plan.

Pruitt's EPA is currently working to scrap that plan, in favor of a far more narrowly targeted program that has yet to be fully rolled out. But Pruitt has not decided how far to go in stripping away the EPA's program to regulate greenhouse gases.

Some conservative activists have urged him to go after the endangerment finding as a means to knee-cap the EPA's ability to address climate change, and Pruitt has variously been reported to be both open to that route and reluctant given the legal fight that would ensue.

From Tuesday's hearing, it sounds like he's still debating it.

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