Scientists, environmentalists and Democratic lawmakers quickly denounced EPA Administrator Scott Pruitt after he said Thursday on CNBC's "Squawk Box" that carbon dioxide is not a primary contributor to climate change.
"I think that measuring with precision human activity on the climate is something very challenging to do, and there's tremendous disagreement about the degree of impact, so no, I would not agree that it's a primary contributor to the global warming that we see," he said.
He added that further study was needed to determine the extent of carbon emmissions' impact on global warming.
Sen. Brian Schatz, D-Hawaii, co-chair of the Senate Climate Action Task Force issued a statement shortly after the interview calling Pruitt's views "extreme" and "irresponsible."
"Anyone who denies over a century's worth of established science and basic facts is unqualified to be the administrator of the EPA. Now more than ever, the Senate needs to stand up to Scott Pruitt and his dangerous views," he said in a statement.
Sen. Tom Carper, the ranking Democrat on the Senate Committee on Environment and Public Works, tweeted about the comment, "I think 97% of the world's scientists were surprised to learn this today! I know I was."
Carper was referring to a frequently cited study that found 97 percent of climate scientists who issued findings on the cause of climate change ascribe the phenomenon to human activity. Those findings have been disputed.
California Sen. Kamala Harris also had a tweet for Pruitt: "It's telling when you're at odds with @NASA, the National Oceanic and Atmospheric Administration, and science generally."
Gina McCarthy, the last EPA administrator, also weighed in, saying, "The world of science is about empirical evidence, not beliefs. When it comes to climate change, the evidence is robust and overwhelmingly clear that the cost of inaction is unacceptably high."
Ben Santer, a climate researcher at the Lawrence Livermore National Laboratory in California, said Pruitt's comment on CNBC was flat wrong.
"The scientific community has studied this issue for decades. The consensus message from many national and international assessments of the science is pretty simple: Natural factors can't explain the size or patterns of observed warming," he said in a statement to Climate Nexus, a communications firm that focuses on climate change and clean energy.
Scientists can demonstrate clearly that recent warming of the planet would not have taken place if it weren't for the change in the composition of the atmosphere, Dr. Kevin Trenberth, distinguished senior fellow a the National Center for Atmospheric Research, told Climate Nexus.
"These are scientific facts, not opinion, and it is incumbent on politicians to take account of the scientific evidence," he said.
With his latest comment, Pruitt's mask has come off, said David Doniger, director of the Climate & Clean Air Program at the Natural Resources Defense Council.
"After obscuring his true views during his Senate confirmation hearings, Scott Pruitt has outed himself as a pure climate denier," he said. "Having an EPA administrator who claims carbon pollution is not the primary cause of climate change is like having a U.S. surgeon general who says smoking is not the primary cause of lung cancer."
In his Senate confirmation hearing, Pruitt said "Science tells us that the climate is changing and that human activity in some manner impacts that change," but added that the degree and extent of that impact remained up for debate.
Pruitt's comment on Thursday is "nothing short of an atrocity," said Aura Vasquez, director of Climate Justice at the Center for Popular Democracy, a group that aims to build organizing power at the state and local level.
"Denying the science of this reality will impact millions of people on the front lines of a dangerously changing climate, especially low-income communities and communities of color," she said.