Environmental Protection Agency Administrator Scott Pruitt drew the ire of several top Democrats and climate change activists after he declared carbon dioxide was not the primary driver of climate change.

Speaking on CNBC's "Squawk Box," Pruitt said there is "tremendous disagreement" on the degree to which CO2 impacts the climate.

"I would not agree that it is a primary contributor to the global warming that we see," Pruitt said.

That remark sparked a firestorm of pushback from liberals on Twitter.

Senator Tom Udall (D-New Mexico) said Pruitt should not be spreading "alternative facts," a reference to a phrase Kellyanne Conway was criticized for using last month.

"The science on CO2 is clear," Udall said.

Senate Minority Whip Richard Durbin (D-Ill.) likened Pruitt's remark to "denying gravity keeps our feet on the ground."

Hawaiian Senator Brain Schatz called Pruitt "nuts."

And, Sierra Club executive director Michael Brune demanded that Pruitt be removed from office for "contradicting science and law."

Watch Pruitt's initial remarks below: