More than two dozen contributors to a widely used reference manual for judges are raising alarm bells about political interference after the deletion of a chapter on climate science.
The uproar is over the latest edition of the Reference Manual on Scientific Evidence, which has been published since 1994 by the Federal Judicial Center, an agency that provides resources to judges. A group of Republican state attorneys general sent a letter to the center on Jan. 29, claiming that the climate chapter was biased and demanding its retraction. About a week later, the center deleted the chapter from its online edition of the nearly 1,700-page manual.
A new letter posted on Monday, signed by 28 experts in science, technology and law who had written other chapters of the manual, strongly criticized the move. The topics they had written about included engineering, neuroscience and toxicology. Their letter was posted online by Science Politics, a publication of Georgetown University’s School of Foreign Service.
“The coordinated effort by 27 state attorneys general to remove that peer-reviewed content is a direct challenge to the independence of the federal judiciary and an attack on a thoroughly vetted exposition of climate science that those attorneys general do not like,” the letter said.
The two most recent editions of the manual were developed with the National Academies of Sciences, Engineering and Medicine, a private organization chartered by Congress in 1863 to advise the nation on technical matters. The National Academies said previously that it stood by the chapter and did not plan to remove it from its website, where it remains accessible.
That resulted in another letter by Republican state attorneys general, led by Austin Knudsen of Montana. On Feb. 19, Mr. Knudsen and 20 of his counterparts wrote to the leadership of the National Academies, calling it “unacceptable” that the organization had allowed the chapter to remain in circulation.
The letter pointed to taxpayer support for the organization and requested a response by March 2. A spokesperson for the National Academies said it had received the letter and would respond in a timely manner.
The letter from the contributors to the manual warned that political interference could potentially affect every scientific discipline relevant to complex litigation. “The political attack by the attorneys general on a carefully and rigorously prepared scientific publication should concern us all,” the letter said.
The number of cases involving climate science has been growing rapidly for the last two decades. The Sabin Center for Climate Change Law at Columbia University tallied about 2,000 cases in American courts as of 2025.
The contributors’ letter said that each chapter had gone through extensive vetting and multiple rounds of revisions. Potential authors had been assessed for their expertise and ability “to write as objectively as humanly possible, and awareness of how that science is used as evidence in litigation,” it said. The work was evaluated by a committee from the National Academies, and then sent to external independent experts for additional review.
“For every edition, including the recently published fourth edition, this extensive vetting has resulted in multiple rounds of revisions that successively improve each draft,” the letter said.
Brenda Eskenazi of the University of California at Berkeley, who is one of the authors of the epidemiology chapter in the newest manual, said that the exhaustive level of review made the politicians’ actions “particularly disturbing.”
“This is just one more example of science being under attack,” said Dr. Eskenazi, who was among the signatories of the letter. “It’s time for us to stand up and say, No, we’ve gone through a process of peer review by other scientists, apart from any political orientation. This is about science.”
Congressional Democrats have called on the center to restore the chapter. More than two dozen lawmakers, led by Senator Ron Wyden of Oregon and Representative Don Beyer of Virginia, sent their own letter to the judicial center on Friday, demanding answers about how the decision to delete it was made.
“At a time when cases implicating climate science are increasing in number and frequency, your decision to capitulate to right-wing pressure and remove this chapter is unconscionable,” they wrote. “It is critical that you restore this chapter and reject all future attempts to intimidate the judiciary into silence.”
It was the first time the manual for judges had included a chapter on climate science. The chapter was written by two experts affiliated with Columbia University: Jessica Wentz, a legal scholar, and Radley Horton, an earth and environmental scientist. They responded this week to the criticisms from the attorneys general in a 10-page document posted on the website of the Sabin Center.
They also noted the existence of a third letter from Republican state attorneys general, to the House and Senate Judiciary Committees on Feb. 2, that urged the committees to investigate and potentially defund the Federal Judicial Center based on their objections to the manual.
Karen Zraick covers legal affairs for the Climate desk and the courtroom clashes playing out over climate and environmental policy.
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