The Trump administration has dismissed the hundreds of scientists and experts who had been compiling the federal government’s flagship report on how global warming is affecting the country.

The move puts the future of the report, which is required by Congress and is known as the National Climate Assessment, into serious jeopardy, experts said.

Since 2000, the federal government has published a comprehensive look every few years at how rising temperatures will affect human health, agriculture, fisheries, water supplies, transportation, energy production and other aspects of the U.S. economy. The last climate assessment came out in 2023 and is used by state and local governments as well as private companies to help prepare for the effects of heat waves, floods, droughts and other climate-related calamities.

On Monday, researchers around the country who had begun work on the sixth national climate assessment, planned for early 2028, received an email informing them that the scope of the report “is currently being re-evaluated” and that all contributors were being dismissed.

“We are now releasing all current assessment participants from their roles,” the email said. “As plans develop for the assessment, there may be future opportunities to contribute or engage. Thank you for your service.”

For some of the authors, that appeared to be a fatal blow to the next report.

“This is as close as it gets to a termination of the assessment,” said Jesse Keenan, a professor at Tulane University who specializes in climate adaptation and was a co-author on the last climate assessment. “If you get rid of all the people involved, nothing’s moving forward.”

The White House did not immediately respond to a request for comment.

The climate assessment is typically compiled by scientists and expert contributors around the country who volunteer to write the report. It then goes through several rounds of review by 14 federal agencies, as well as a public comment period. The entire process is overseen by the Global Change Research Program, a federal group established by Congress in 1990 that is supported by NASA.

Under the Trump administration, that process was already facing serious disruptions. This month, NASA canceled a major contract with ICF International, a consulting firm that had been supplying most of the technical support and staffing for the Global Change Research Program, which coordinates work among hundreds of contributors.

President Trump has frequently dismissed the risks of global warming. And Russell Vought, the current director of the Office of Management and Budget, wrote before the election that the next president should “reshape” the Global Change Research Program, because its scientific reports on climate change were often used as the basis for environmental lawsuits that constrained federal government actions.

Mr. Vought has called the government’s largest climate research unit, a division inside the National Oceanic and Atmospheric Administration, a source of “climate alarmism.”

During Mr. Trump’s first term, his administration tried, but failed, to derail the National Climate Assessment. When the 2018 report came out, concluding that global warming posed an imminent and dire threat, the administration made it public the day after Thanksgiving in an apparent attempt to minimize attention.

In February, scientists had submitted a detailed outline of the next assessment to the White House for an initial review. But that review has been on hold and the agency comment period has been postponed.

It remains to be seen what happens next with the assessment, which is still mandated by Congress. Some scientists feared that the administration might try to write an entirely new report from scratch that downplays the risks of rising temperatures or contradicts established climate science.

“There may well be a sixth National Climate Assessment,” said Meade Krosby, a senior scientist at the University of Washington’s Climate Impacts Group and a contributor to the assessment. “The question is whether it is going to reflect credible science and be of real use to our communities as they prepare for climate change.”

Scientists involved in earlier climate assessments have said the report is invaluable for understanding how climate change would affect daily life in the United States.

“It takes that global issue and brings it closer to us,” Katharine Hayhoe, a climate scientist at Texas Tech University, said this month. “If I care about food or water or transportation or insurance or my health, this is what climate change means to me if I live in the Southwest or the Great Plains. That’s the value.”

Many state and local policymakers, as well as private businesses, rely on the assessment to understand how climate change is affecting different regions of the United States and how they can try to adapt.

And while the scientific understanding of climate change and its effects hasn’t changed drastically since the last assessment in 2023, Dr. Keenan of Tulane said, there has been a steady progression of research on what communities can do to prepare for worsening wildfires, higher sea levels and other problems exacerbated by rising temperatures.

Decision makers forced to refer to the last assessment would be relying on outdated information on what adaptation and mitigation measures really work, scientists said.

“We’d be losing the cornerstone report that is supposed to communicate to the public the risks we face with climate change and how we can move forward,” said Dustin Mulvaney, a professor of environmental studies at San Jose State University who was an author on the southwest regional chapter. “It’s pretty devastating.”