NASA Administrator Jim Bridenstine, who previously questioned whether humans are primarily responsible for climate change, left no doubt Wednesday that his position has changed. Signifying a striking conversion, he confirmed that he now accepts that humans are, in fact, the leading cause.

During testimony before the Senate Appropriations subcommittee on commerce, justice, science and related agencies, Sen. Brian Schatz (D-Hawaii) asked Bridenstine whether he believes greenhouse gases are the primary cause of climate change. Bridenstine quickly replied in the affirmative.

“The National Climate Assessment, that includes NASA, and it includes the Department of Energy, and it includes NOAA, has clearly stated it is extremely likely, [that] is the language they use, that human activity is the dominant cause of global warming, and I have no reason to doubt the science that comes from that,” Bridenstine said.

Schatz followed up by asking, “Is it fair to call this an evolution of your views?”

Bridenstine replied: “Yes.”

On further questioning from Schatz, Bridenstine also committed to defending the independence and integrity of climate science at NASA.

Schatz thanked Bridenstine for his evolved stance. “I have come to the conclusion that this is a true evolution. That you respect people with whom you work, you respect the science, you want their respect. And there is no way to move forward if you’re going to be undermining the science. So I’m really pleased to see this change,” the senator said.

At his confirmation hearing before the Senate in November, Bridenstine’s responses to a similar line of questioning were much more nuanced and opaque. When asked whether human activity was the primary cause of climate change, he said, “It’s going to depend on a lot of factors, and we’re still learning more about that every day.”

Bridenstine’s position on climate change presents a sharp departure from those of President Trump and high-ranking administration officials, such as Environmental Protection Agency Administrator Scott Pruitt, who have pointedly called into question the degree to which humans contribute.

His evolved views are also notable for a former Republican congressman from Oklahoma. Research published in the journal Climatic Change in 2016 found just 31 percent of Republicans in Oklahoma (and nationwide) agreed that global warming is caused mostly by human activities.