Jeffrey Bossert Clark, who represented BP in lawsuits over the nation's largest oil spill and has repeatedly challenged the science of climate change, was confirmed Thursday by the Senate to serve as the nation's top environmental lawyer—a key position for the defense of President Donald Trump's regulatory rollback.

Lawmakers voted 52 to 45 to confirm Clark to serve as assistant attorney general for environment and natural resources.

In that post, Clark will steer the federal government's defense of the slew of legal challenges the Trump administration faces over its repeal of environment and climate regulations. He also will be responsible for taking polluters and other environmental lawbreakers to court as head of the Justice Department's Environment and Natural Resources Division.

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Clark has represented numerous oil industry clients as a partner in the Washington, D.C., office of Kirkland & Ellis, including defending BP in lawsuits by fishing businesses and others who sued the oil company in the wake of the 2010 Deepwater Horizon disaster in the Gulf of Mexico.

Clark also represented the U.S. Chamber of Commerce in lawsuits challenging the federal government's authority to regulate carbon emissions. In court, he repeatedly argued that it is inappropriate to base government policymaking on the scientific consensus presented by the UN's Intergovernmental Panel on Climate Change (IPCC).

"When did America risk coming to be ruled by foreign scientists and apparatchiks at the United Nations?" Clark demanded in a 2010 blog post on the EPA's endangerment finding. In a 2010 talk at a convention of the conservative Federalist Society, he said the Obama administration's policies to reduce greenhouse gas emissions were "reminiscent of kind of a Leninistic program from the 1920s to seize control of the commanding heights of the economy."

In 2016, he filed a "friend of the court" brief against the Clean Power Plan, the nation's first limits on carbon emissions from power plants, on behalf of a non-profit group that opposes regulation, Consumers' Research. Environmental groups could use that as a basis to seek Clark's recusal in the inevitable litigation ahead over the Trump administration's Clean Power Plan repeal.

Critics of Clark pointed out that the Senate was confirming someone who had called the science of climate change "contestable" during a week when a Category 4 hurricane hit the Southeast and the IPCC warned that time is running out to head off catastrophic warming.

Clark is "exactly the wrong person to be in this job of enforcing regulations to clean up our environment," said Sen. Dick Durbin (D-Ill.) the minority whip.

But Senate Majority Leader Mitch McConnell (R-Ky.) praised Clark for his background as a litigator. "Mr. Clark's legal colleagues describe him as one of the most capable lawyers with whom they've ever worked," he said.

Two Democrats who are facing tough re-election battles in red-leaning states, Sens. Joe Manchin of West Virginia and Claire McCaskill of Missouri, joined Republicans in voting to confirm Clark. Sen. Heidi Heitkamp of North Dakota, now seen as the most endangered red-state Democrat in November, did not vote. The two Florida senators, Democrat Bill Nelson and Republican Marco Rubio, were focused on the devastation in their state in the wake of Hurricane Michael and also didn't vote on Clark's confirmation.

Clark, who was nominated for the post more than a year ago, was one of nearly 200 Trump appointees awaiting confirmation, according to the Partnership for Public Service.