Scott Pruitt's remarks put him at odds with overwhelming scientific consensus and even his own agency's stance
The head of the Environmental Protection Agency in the US has been criticised after questioning carbon dioxide's role in global warming.
When asked on CNBC if he believed carbon dioxide was 'the primary control knob for climate', Scott Pruitt claimed: "No. 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. But we don't know that yet - we need to continue the debate and continue the review and the analysis."
The statement directly contradicts the EPA's own stance on CO2 and climate change.
"Carbon dioxide is the primary greenhouse gas that is contributing to recent climate change," the agency says on its website.
It adds that while much CO2 is absorbed and emitted naturally, human activities "release large amounts of CO2, causing concentrations in the atmosphere to rise".
Overwhelming scientific consensus points towards society's impact on the environment, with NASA saying that increased CO2 concentration from human activity since the Industrial Revolution is "the most important long-lived 'forcing' of climate change".
Mr Pruitt's comments drew swift condemnation from climate activists and scientists, including from his predecessor Gina McCarthy.
In a statement, Mrs McCarthy said: "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.
Insisting that preventing the consequences of climate change is imperative for the good of everyone 'who calls Earth home', she added: "I can not imagine what additional information the administrator might want from scientists for him to understand that."
The White House downplayed the comments, with Press Secretary claiming the controversial remarks were 'just one snippet' of what Mr Pruitt said.
Mr Pruitt, who previously served as the Oklahoma Attorney General, was one of the most controversial appointments by President Donald Trump.
Pruitt was a vocal critic of Barack Obama's policies on climate change. He has previously questioned the overwhelming scientific consensus on human-influenced climate change.