The Trump administration has halted U.S. scientists' participation in key U.N. climate change assessments, marking another step in its retreat from international climate efforts. The decision affects researchers working with the Intergovernmental Panel on Climate Change (IPCC).

The White House has ordered staff from the U.S. Global Change Research Program and the National Oceanic and Atmospheric Administration (NOAA) to stop work with an IPCC working group, sources told Reuters.

As a result, the U.S. will not attend a major IPCC plenary meeting in Hangzhou, China, next week, where discussions will shape the next global climate assessment, including policies on carbon capture and removal.

Climate experts have raised concerns over the withdrawal, warning it could weaken the IPCC’s role in providing a shared global understanding of climate risks and mitigation strategies.

“The U.S. being completely removed from that process is concerning,” said Delta Merner of the Union of Concerned Scientists.

Despite the halt, American researchers will continue contributing to climate studies used by the IPCC. However, the absence of official U.S. participation is expected to be significant.

China’s foreign ministry said it was unaware of the U.S. decision. The U.S. previously co-chaired a working group on climate mitigation alongside Malaysia and had pledged $1.5 million to support the IPCC—funds that remain unapproved by Congress.

Climate scientists say the move aligns with Trump’s broader efforts to withdraw from international climate agreements, including his second exit from the Paris accord and reductions in global climate finance.

“This would align with Trump's signals around climate action,” said Kathryn Bowen, an IPCC lead author and professor at Melbourne University. She also noted declining international funding for climate science, which could impact research, particularly in developing nations.

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