When a cautious, science-based and largely apolitical group like the United Nations Intergovernmental Panel on Climate Change says the world must utterly transform its energy systems in the next decade or risk ecological and social disaster, attention must be paid.

The panel, created in 1988 , synthesizes the findings of leading climate scientists, an undertaking for which it received the 2007 Nobel Peace Prize. It is not in the habit of lecturing governments. But its latest report, issued near Seoul on Monday, is very different. One United Nations official described it as “a deafening, piercing smoke alarm going off in the kitchen” — an alarm aimed directly at world leaders. “Frankly, we’ve delivered a message to the governments,” said Jim Skea, a co-chairman of the panel and a professor at Imperial College, London. “It’s now their responsibility … to decide whether they can act on it.”

Unfortunately, no alarm seems loud enough to penetrate the walls of the White House or the cranium of its principal occupant. President Trump had nothing substantive to say about the report, preferring, his staff said, to focus on celebrating the elevation of Brett Kavanaugh to the Supreme Court. Having already announced that he would withdraw the United States from the 2015 Paris agreement on climate change, having also rolled back a suite of Obama-era efforts to reduce greenhouse gas emissions, Mr. Trump thus reaffirmed his sorry role as an outlier in the global struggle against climate change — a struggle few believe can be won without the enthusiastic participation of the United States.

The report, written by 91 scientists from 40 countries, came about at the request of several small island nations that took part in the Paris talks, where 195 countries pledged their best efforts to limit increases in global warming to 3.6 degrees (2 degrees Celsius) above preindustrial levels. Fearing that their countries might someday be lost to rising seas, they asked the intergovernmental panel for further study of a lower threshold, 2.7 degrees Fahrenheit (1.5 degrees Celsius). The panel’s report concluded that the stricter threshold should become the new target. The alternative is catastrophe — mass die-offs of coral reefs, widespread drought, famine and wildfires, and potentially conflict over land, food and fresh water.