Neil deGrasse Tyson—astrophysicist, author and director of the Hayden Planetarium at New York's Natural History Museum—joined Stephen Colbert Tuesday night to weigh in on claims made by Trump's new EPA head.

Scott Pruitt "said he does not believe CO2 is the control knob for climate change," Colbert reminded his guest. "What is the present consensus of CO2 and climate change?"

"It's a greenhouse gas," Tyson answered. 

"People just talk," he continued. "I can't chase what people say because it flutters with the breeze."

Tyson warned that if Pruitt "puts down some legislation that requires that everyone [must go along with his beliefs], oh! Oh, my god! Hold me back!" he exclaimed. 

"I'll hold you back," Colbert offered. "He's going to blow," he told the audience. "He's a crystal geyser!"

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