Former New York congressman Lee Zeldin, president-elect Donald J. Trump’s nominee to run the Environmental Protection Agency, told senators on Tuesday that he would “enthusiastically uphold” the agency’s mission to protect human health and the environment and that he grasped the basic science of climate change.
But in a back and forth with Senator Edward J. Markey, Democrat of Massachusetts, Mr. Zeldin would not commit to aggressively regulating greenhouse gases from from smokestacks and tailpipes in the way that the agency under President Biden had. Carbon emissions from transportation and power plants are chief drivers of global warming.
Instead at his confirmation hearing before the Senate Environment and Public Works Committee, Mr. Zeldin repeatedly said that the agency’s mission is to ensure “clean air and clean water” but did not flag climate action as a central responsibility.
Mr. Zeldin’s tone was markedly different from that of the future president, who has called climate change a hoax and vowed to “kill” many major E.P.A. rules, particularly on climate change. People close to the Trump transition have also recommended ousting E.P.A. career staff, eliminating its scientific advisers, and closing an office that helps minority communities that disproportionately struggle with polluted air and water.
The nomination of Mr. Zeldin, 44, who ran unsuccessfully for governor of New York in 2022, baffled many, since he has little background in environmental regulation.
He struggled to answer detailed questions about chemical recycling by Senator Jeff Merkley, Democrat of Oregon. “I would look forward to an opportunity to be able to read what you’re referencing,” Mr. Zeldin said.
Still, Mr. Zeldin and his allies point to his years representing his Long Island district, which included miles of coastline and had a bipartisan tradition of environmental conservation. He is a Trump supporter who voted against certifying the results of the 2020 election. Friends say he has a long and loyal connection with the president-elect.
In his opening statement to the committee, Mr. Zeldin said, “I strongly believe we have a moral responsibility to be good stewards of our environment for generations to come. It’s been so motivating to see the tremendous talent stepping up to serve at the EPA. I couldn’t be more excited to partner with our EPA team nationwide, to exceptionally serve the American public.”
He also said, “I will foster a collaborative culture within the agency, supporting career staff who have dedicated themselves to this mission.”
When Senator Sheldon Whitehouse, Democrat of Rhode Island and one of the loudest voices on Capitol Hill for climate action, grilled the nominee on the basic science of climate change, Mr. Zeldin waffled at first but ultimately produced a correct answer.
“What is the effect of carbon dioxide emissions from fossil fuel combustion?” Mr. Whitehouse asked Mr. Zeldin, referring to the legally designated pollutant that is the chief cause of the global warming that is dangerously heating the planet.
Initially, Mr. Zeldin tried to evade the question. “While I am someone who believes strongly that science and policymakers should work together, I think we have many talented scientists who provide that research,” he said.
But when Mr. Whitehouse pressed, Mr. Zeldin responded accurately: “Trapping heat, sir,” adding “Greenhouse gases trap heat.”
Mr. Zeldin said he would support the career employees at the E.P.A. That stood in contrast to the approach of Mr. Trump’s first E.P.A. administrator in his first term, Scott Pruitt, who viewed career employees at the agency as antagonists, openly denied the science of climate change, and oversaw an era in which the nation’s top regulator of air and water pollution and industrial chemicals saw its budget slashed, leading to an exodus of employees and weakened enforcement of environmental rules.
Lisa Friedman contributed reporting.
