They are among the members of the Intergovernmental Panel on Climate Change, a group of scientists convened by the United Nations to make recommendations to world leaders. Their report, issued Monday, warns of environmental catastrophe as early as 2040 and advises that the worst can be staved off only if civilization is transformed more profoundly than at any point in recorded history.

President Trump, in comments to reporters Tuesday on the South Lawn, seemed unaware of the IPCC, as the body is known, and expressed doubts about its determinations. The remarks put him at odds with most world leaders, as well as with scientific fact — a familiar position for the brash former businessman who has long ridiculed climate concerns.

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“It was given to me. It was given to me, and I want to look at who drew, you know, which group drew it,” the president said, as Hurricane Michael edged closer to the Florida’s northern Gulf Coast, threatening devastating flooding, which scientists say is exacerbated by rising sea levels.

Trump said some reports were good, while others were not as good.

“Because I can give you reports that are fabulous, and I can give you reports that aren’t so good,” he added.

The 700-page report includes drawings of sorts — graphs and other visual renderings. But it is mostly detailed analysis, dense with citations, of the effects of surpassing 1.5 degrees Celsius (2.7 degrees Fahrenheit) of warming over preindustrial levels.

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A 33-page summary for policymakers includes four main points, A through D, each with an elaborate set of sub points, arranged in digestible paragraphs.

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It anticipates skepticism. For each finding, the authors report a level of confidence, from very low to very high, “grounded in an evaluation of underlying evidence and agreement.” For instance, the scientists have “high confidence” that human activities are contributing to significant warming and “very high confidence” that partnerships with nonstate actors, such as the banking system and scientific institutions, would help limit warming to livable levels.

Trump assured reporters: “But I will be looking at it, absolutely.” Yet he famously doesn’t read much, so the chances that he will look at it, let alone read it, are in question.

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He has scorned climate science and promised to yank the United States from the Paris climate agreement, which gave rise to the report issued this week.

Meanwhile, he has pledged to speed up the burning of coal, which the report warns would block pathways to keeping warming below 1.5 degrees Celsius. And just Monday, the Trump administration announced that the Environmental Protection Agency would be changing a rule to allow year-round sales of E15, or fuel that is 15 percent ethanol by volume.

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“I want more industry. I want more energy. I want more,” Trump told reporters Tuesday before leaving for a rally in Iowa. He said he was dissatisfied with the current price of crude oil per barrel, $74.

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“I want low prices, so I’m okay with it,” he added. “You know, it’s an amazing substance. You look at the Indy cars. They run 100 percent on ethanol.”

Sen. Charles E. Grassley (R-Iowa) hailed the plan to lift the ban on summer sales of high-ethanol blends, calling the long-expected White House announcement “a very good victory for agriculture.” As chairman of the Senate Judiciary Committee, Grassley has just finished leading the Republicans in a successful battle to confirm Brett M. Kavanaugh, Trump’s nominee, to the Supreme Court.

Trump called the notion that year-round sales have a negative effect — the EPA previously cited smog concerns — a “misnomer,” which is actually a misnomer, meaning an inaccurate use of a term.

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Conspiracy theories about the climate fill Trump’s Twitter page. He has called global warming a “canard,” speculated about global cooling and, on Election Day in 2012, claimed that “global warming was created by and for the Chinese to make U.S. manufacturing noncompetitive.” He frequently cites weather reports about rain and snow to argue, contrary to scientific consensus, that the planet can’t be warming.

“By the way, it’s supposed to be 70 degrees today. It’s freezing. Speaking of global warming, where is — we need some global warming!” he shouted in April 2016 during a rally in Rochester, N.Y.

The EPA’s acting administrator, Andrew Wheeler, told The Washington Post recently that the United States would remain engaged in U.N. work on climate change, despite Trump’s stated plan to withdraw from the Paris accord. But he declined to specify a level at which the country would seek to keep warming.

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Meanwhile, the administration has made its own climate predictions. A 500-page impact statement drawn up over the summer by the National Highway Traffic Safety Administration assumed that the planet would warm a calamitous seven degrees Fahrenheit by the end of the century.

The statement, meant to rationalize Trump’s decision to freeze certain fuel-efficiency standards, argued that temperatures would rise that amount over the average between 1986 and 2005 whether or not the Obama-era guidelines in question were stalled. From preindustrial levels, the analysis assumed a rise of about four degrees Celsius, or seven degrees Fahrenheit, vastly more than the U.N. panel says is sustainable.

This sort of increase, scientists say, would have disastrous consequences. It could put parts of Manhattan and Miami underwater, while causing heat waves that suffocate whole swaths of the world.

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