Speaking in South Carolina at a rally of 10,000 supporters, Donald Trump addressed a plethora of issues facing the nation. In his speech, Trump criticized President Barack Obama’s concern for climate change.

“Can you believe this?” Trump asked the riled up crowd. “Global warming. I’ll tell you what our biggest problem is and I hate to even say it: Our biggest problem is nuclear warming. That’s our biggest problem. And unless we’re smart—and I mean smart and tough and cunning—there’re gonna be problems like you’ve never seen.”

“You think Paris was bad?” Trump added. “You think that’s bad? You think that’s bad? We better get smart.”

Trump has previously expressed skepticism that climate change is a problem to be addressed.