The first presidential debate did not include a direct line of questioning on climate change, despite pleas from several different outlets for NBC News moderator Lester Holt to bring it up in the context of the economy, but the matter came up briefly in an exchange between former Secretary of State Hillary Clinton and Donald Trump.

“Donald thinks that climate change is a hoax perpetrated by the Chinese,” Clinton said, referring to a Trump tweet from 2012 that has since been deleted from his account. “I did not,” Trump interrupted. “I did not say that. I do not say that.” He further said: “Now, look, I’m a great believer in all forms of energy. But we’re putting a lot of people out of work. Our energy policies are a disaster. Our country is losing so much in terms of energy.”

In other instances in 2013 and 2014, Trump took to Twitter to mock climate change, and in interviews throughout the campaign, has expressed skepticism that the problem is caused by human activity or warrants a plan of action.