NASA Administrator Jim Bridenstine used to deny climate change and humans' role in rising global temperatures.

His views have evolved, however, and he now supports the mainstream scientific consensus that human activity is causing Earth's climate to change on an unprecedented scale.

He told The Washington Post in a recent interview that his views changed because he "read a lot."

NASA Administrator Jim Bridenstine explained to The Washington Post on Tuesday why his position on climate change has evolved.

In a 2013 speech on the House floor, Bridenstine, a former three-term Republican congressman from Oklahoma who served as a pilot in the Navy, denied the scientific consensus on climate change, saying that "global temperatures stopped rising 10 years ago."

But now, as the head of NASA — an agency that funds a lot of research on climate change — Bridenstine has changed his tune. He agrees with the scientific consensus that humans' burning of fossil fuels is spewing greenhouse gases like carbon dioxide into the atmosphere, causing global temperatures to rise.

Skye Gould/Business Insider

"I heard a lot of experts, and I read a lot," Bridenstine told The Post. "I came to the conclusion myself that carbon dioxide is a greenhouse gas that we've put a lot of it into the atmosphere and therefore we have contributed to the global warming that we've seen."

This acceptance of climate science is common among Democrats, but many Republicans deny it.

A year ago, President Donald Trump announced his intention to pull the US out of the Paris climate agreement, a global accord designed to prevent the Earth's average temperature from rising more than 2 degrees Celsius above pre-industrial levels. In Trump's announcement, he said that "we're not going to put our businesses out of work" to reduce carbon emissions.

Scott Pruitt, the Environmental Protection Agency administrator, told CNBC in an interview in March that he didn't think humans were causing climate change, saying there's "tremendous disagreement about the degree of impact." A federal judge ruled this week that Pruitt must provide scientific evidence to back up his claim.

Recent research suggests that the global average temperature will increase to 3.2 degrees Celsius above pre-industrial levels by the end of this century. Already, we've seen a rise of nearly 1 degree, something that scientists say was caused mainly by human activity.

"I don't deny that consensus that the climate is changing," Bridenstine said last month in a town-hall meeting for NASA employees. "That is absolutely happening, and we are responsible for it."