WASHINGTON—The Trump administration faces a deadline at the end of next week on whether to approve a scientific report that verifies climate change and attributes it to humans, a position that contradicts some of the rhetoric the president used during his 2016 campaign.

The White House’s Office of Science and Technology Policy is supposed to decide by Aug. 18 whether to approve or recommend changes to the “Climate Change Special Report,” the research on climate science that feeds its National Climate Assessment. That document, mandated by Congress, is a quadrennial government analysis of the effects of climate change in the U.S. Its last version, in 2014, concluded climate change cost the economy billions of dollars through flooding, droughts and other disasters in every region of the country.

The initial draft of the current report documents thousands of studies that show a changing climate with the hottest temperatures in 1,700 years, the fastest-rising seas in more than 2,000 years and a five- to 10-fold increase in U.S. coastal flooding since the 1960s. New scientific advances since 2014 also show more clearly that climate change and extreme weather events come from humans, the draft report said.

“Many lines of evidence demonstrate that human activities, especially emissions of greenhouse gases, are primarily responsible,” it said. “There are no alternative explanations.”

That is at odds with President Donald Trump’s Environmental Protection Agency administrator, Scott Pruitt, who has said it is “very challenging” to be precise about humans’ role in climate change. And the president himself, while campaigning, called global warming a “hoax.”


“So Obama’s talking about all of this with the global warming and the—a lot of it’s a hoax, it’s a hoax,” Mr. Trump said at a campaign stop in Hilton Head, S.C. in December 2015.

The scientific draft has been through several versions, one publicly available since late last year. The New York Times reported about the latest draft on Tuesday. Environmental groups and scientists say they are concerned that the Trump administration might try to change or quash the findings. The White House criticized the Times’s article but declined to discuss details.

“Drafts of this report have been published and made widely available online months ago during the public comment period,” White House press secretary Sarah Huckabee Sanders said. “The White House will withhold comment on any draft report before its scheduled release date.”

The Aug. 18 deadline is set by the U.S. Global Change Research Program, the administrative unit created by Congress in part to manage the assessment, said Katharine Hayhoe director of the Texas Tech University Climate Science Center and a lead author of the report. That deadline is to ensure that the scientific report gets released by this autumn so the National Climate Assessment can then publish in late 2018.


This would be only the fourth assessment in 28 years, though Congress required one every four years. Two of the prior three assessments were published during Barack Obama’s presidency.

Mr. Trump has reversed several Obama-era environmental policies, most notably announcing in June he planned to withdraw the U.S. from the Paris climate accord. Mr. Pruitt is reportedly considering an exercise that would serve as sort of a public debate in which the science of climate change would be thoroughly and publicly discussed. Backers of this concept say there are questions about humans’ role in climate science and that a public airing of the debate would be the best approach.

Scientists and environmentalists say the draft scientific report shows how there is no longer a legitimate debate on whether the climate is changing and whether humans are responsible. And by bringing more attention to the report before the White House’s decision, the authors made it more difficult for potentially hostile political leaders to meddle with those findings, those environmentalists and scientists said.

“It’s scientifically bulletproof,” said Jeremy Symons, associate vice president at the Environmental Defense Fund. “This report takes us past questions of science to focus on solutions.”


—Eli Stokols contributed to this article.

Write to Timothy Puko at tim.puko@wsj.com