Trump, who has dismissed climate change as bullshit and a Chinese hoax , pledged in May to pull the U.S. out of the historic Paris climate agreement a promise that didnt sit well with hundreds of American businesses or many of the worlds leading scientists , including famed physicist Stephen Hawking.

Asked during Mondays press conference if he could confirm reports that Trump planned to withdraw the U.S. from the global pact, White House Press Secretary Sean Spicer said he had no additional information. In April, nearly 200 countries pledged to drastically reduce carbon emissions in an effort to limit the rise in global temperatures.

John Coequyt, global climate policy director of the Sierra Club, was among those who blasted Ebells comments, saying that to pull out of the climate pact would be a mistake of world historic consequence.

Its the kind of wildly irresponsible action that you couldnt imagine an American president taking until last week, he said in a statement on Monday. Our planet is in crisis and we must do everything in our power to tackle it, not move backward.

In September, U.S. President Barack Obama and Chinese President Xi Jinping fortified commitments to reduce carbon emissions by formally joining the Paris agreement and pledging a continued bilateral climate cooperation. The U.S. and China are the worlds two largest emitters of greenhouse gases.

Xi has since warned Trump against withdrawing from the agreement, calling it a hard-won achievement that all signatories should stick to.

Ebell, who directs environmental and energy policy at the anti-regulation Competitive Enterprise Institute , has a long history of denying climate change and opposing global efforts aimed at combatting it.

In a 2005 column in The Guardian, Ebell wrote that policies proposed to deal with global warming such as the Kyoto protocol pose a much greater threat to human flourishing than does global warming.