The comment marks a shift for the former Texas governor who had previously called the science behind climate change “unsettled” and a “contrived, phony mess.” It also clashes with Trump’s statements during his campaign for the White House that global warming is a hoax meant to weaken U.S. business.

“I believe the climate is changing. I believe some of it is naturally occurring, but some of it is also caused by man-made activity. The question is how do we address it in a thoughtful way that doesn’t compromise economic growth, the affordability of energy, or American jobs,” Perry said.

Trump, who will be sworn in as president on Friday, has vowed to slash U.S. regulations curbing carbon dioxide emissions and has suggested pulling America out of a global climate change pact signed in Paris in 2015.

Perry, 66, was governor of Texas from 2000 to 2015, making him the longest-serving governor of the oil-producing state in its history. He is seen by Trump as someone who can usher in jobs growth in the oil, gas and coal industry.

As energy secretary, he would lead a vast scientific research operation credited with helping trigger a U.S. drilling boom and advancements in energy efficiency and renewables technology, and would oversee America’s nuclear arsenal.

The former Texas governor said during the hearing that he also regrets having previously called for the department’s elimination, during his failed bid for the Republican presidential nomination in 2012.

That proposal, which has become known as his “oops” moment, came during a Republican presidential candidate debate when he could not initially remember all of the three Cabinet-level departments he wanted to eliminate – the departments of Commerce, Education and Energy.

“After being briefed on so many of the vital functions of the Department of Energy, I regret recommending its elimination,” he said in his opening remarks to the Senate Committee on Energy and Natural Resources.

Protect the Scientists

Democrats on the committee expressed worry that Perry would weaken the energy department’s functions and potentially target its army of scientists focused on climate research.

Perry sought to assuage them.

“I am going to protect the men and women of the scientific community from anyone who would attack them,” he said in response to a question from Democratic Senator Maria Cantwell of Washington about whether he would cut the budget of climate science at the department.

He also distanced himself from a questionnaire the Trump transition team sent to the department in December demanding names and publications of employees who had worked on climate issues. After an uproar by critics who said it amounted to a witch hunt, the team disavowed the survey.

“I didn’t approve it. I don’t approve of it. I don’t need that information. I don’t want that information,” Perry said on Thursday.

Perry said much of his focus running the department would be on renewing America’s nuclear weapons arsenal.

“As a former Air Force pilot during the days of the Cold War, I understand the deterrent value of our nuclear weapons systems, and the vital role they play in keeping the peace,” he said.

More than half of the department’s $32.5 billion budget goes to maintaining the U.S. nuclear weapons arsenal and cleaning up the country’s nuclear waste legacy from the Cold War.

The New York Times said on Thursday that Perry was unaware of the size of the nuclear role that the department plays when he accepted the job last year.

Perry also said that he would support a bill in Congress backing a state’s right to block nuclear waste sites if Congress passes it into law. Nuclear waste siting is a major hurdle for expanding the U.S. nuclear power sector.

Department leadership under Perry would represent a pivot from being run by learned scientists to a person who is known for close ties to energy interests.

Current Energy Secretary Ernest Moniz is a nuclear physicist who led technical negotiations in the 2015 Iran nuclear deal, while the previous head, Steven Chu, is a Nobel Prize-winning physicist.

Perry resigned from the board of directors of Energy Transfer Partners LP, the company building the Dakota Access Pipeline opposed by Native Americans and environmentalists.