NASA Administrator Jim Bridenstine sparred with Sen. Brian Schatz during his confirmation hearing last fall over whether human activity was a contributor to or the primary cause of climate change.
Now Schatz is praising Bridenstine for what the Hawaii Democrat described as "an act of common sense and courage" after the administrator said he now accepts that humans are primarily responsible for climate change.
During a Senate appropriations subcommittee hearing Wednesday, Schatz asked Bridenstine whether he believed that greenhouse gases were the primary cause of climate change.
Bridenstine, a former Oklahoma Republican congressman, replied that he did.
"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 -- is the language they use -- that human activity is the dominant cause of global warming," Bridenstine said.
"I have no reason to doubt the science that comes from that," he added.
Schatz then asked Bridenstine if he agreed "with the scientific consensus, which includes many NASA researchers, that the climate is changing and humans are the leading cause.
Bridenstine again said he did, and, when asked by Schatz, agreed that it was accurate to call it an evolution of his views. He also said, when asked by Schatz, that he would commit to funding, independence and integrity of climate science at NASA "without question."
Schatz thanked Bridenstine for his answers and said he wanted to recognize the administrator's "evolution on this issue."
"I think it's essential for one of the premier science agencies of the federal government for you to abide by the science," Schatz said. "We needed to move through this period of sort of ideological disagreement, political disagreement, and back to the point where the NASA administrator is a leader of a science agency. And you can't lead a science agency if you are not grounded by the science."
Schatz said he had come to the conclusion that Bridenstine had undergone a "true evolution" and added that he was "really pleased to see this change."
In response to CNN's request for comment, Bridenstine said in a statement:
"I appreciate Senator Schatz and all of the Subcommittee's questions and look forward to working closely with them on NASA related issues. NASA employees include some of the greatest scientists in the world and as the head of NASA I will continue to seek their guidance and counsel while we work to achieve the President's goal of getting the United States back to the moon, to Mars, and beyond."
Bridenstine was confirmed to lead NASA last month in a close and dramatic Senate vote, with many Democratic lawmakers opposing his nomination. For some, that was because he is the first elected official to serve as NASA administrator. Other opponents viewed him as a denier of climate change.
Following the hearing Wednesday, Schatz tweeted that he had "fought Bridenstine to run NASA because he was a climate denier."
"He has since changed his mind, and has confirmed that climate change is caused by humans. This is an act of common sense and courage," Schatz added.
"I don't want to overstate it, but it also shows that people of good faith, when exposed to the facts, can in fact acknowledge the reality of what we are doing to our planet," he said in a later tweet. "Our politics are broken but I still have endless faith in people."