Sen. John McCain (R-AZ) on Sunday said he can’t guess why some fellow Republicans deny the scientific consensus that climate change exists and is affected by human activity.

“I don’t know because I can’t divine their motives,” McCain said on CNN’s “State of the Union.”

“There is things happening with the climate in the world that is unprecedented,” he added. “We have to understand that the climate may be changing and we can take commonsense measures which will not harm the American people.”

McCain also said an agreement President Donald Trump came to with Democrats for a short-term increase in the debt limit “was not an exercise in bipartisanship.”

“The Republicans leaders, Ryan and McConnell, were surprised to hear that he had cut this deal with Chuck and Nancy,” McCain said, referring to House Speaker Paul Ryan (R-WI), Senate Majority Leader Mitch McConnell (R-KY), and their Democratic counterparts House Minority Leader Nancy Pelosi (D-CA) and Senate Minority Leader Chuck Schumer (D-NY).

“The proposal that the President accepted, the speaker of the House had just categorically rejected,” McCain said. “So that’s not the way we need to do business.”