A federal agency has deleted a chapter on climate science from a reference manual for judges after complaints from 27 Republican state attorneys general.
In recent weeks the officials had written to the Federal Judicial Center, an office that provides resources to judges nationwide, alleging that the climate chapter in the manual was biased. On Friday, Attorney General John B. McCuskey of West Virginia made public the text of a Feb. 6 letter from Judge Robin L. Rosenberg, the center’s director, stating that the chapter on climate change had been removed.
“In response to your letter dated January 29, 2026, I write to inform you that the Federal Judicial Center has omitted the climate science chapter from the Reference Manual on Scientific Evidence, Fourth Edition,” it said.
There was no further explanation, and the center declined to comment.
In recent years the courts have become an increasingly important battleground for climate policy. The role of judges in resolving those disputes was elevated further by a 2024 Supreme Court decision overturning a longstanding principle, known as the Chevron deference, of courts deferring to the knowledge and decisions of federal agencies.
That has added to the burden on judges to understand the complexities of scientific issues like climate change when hearing cases.
The end of the Chevron deference means that judges “must more carefully assess scientific evidence when interpreting the law,” said Delta Merner, lead scientist for the Science Hub for Climate Litigation at the Union of Concerned Scientists, an advocacy group. “That elevates the importance of clear, well-supported science in the courtroom and robust standards for evaluating expert testimony.”
The Federal Judicial Center was created by Congress in the 1960s to assist the judiciary with research and continuing education, and its board is led by the chief justice of the United States. The manual is a joint product of the center and the National Academies of Sciences, Engineering, and Medicine, a private nongovernmental group operating under a Congressional charter signed by Lincoln to advise the nation on issues related to science and technology.
The fourth edition of the manual, totaling nearly 1,700 pages, was issued last year. The climate chapter remains available in the version posted to the National Academies’ website. A spokesperson said the organization stood by the chapter.
Other topics in the manual include artificial intelligence, DNA identification and epidemiology.
It was the first time the manual had included a chapter on climate science, according to Jessica Wentz, a legal expert who wrote the chapter with Radley Horton, an earth and environmental scientist. Both are affiliated with Columbia University. Ms. Wentz said she had spent “hundreds of hours” on the chapter since 2023.
“We endeavored to make it a neutral but comprehensive assessment of the science, and it underwent an extensive peer review process,” Ms. Wentz said. “The goal was to provide foundational information about climate science to help judges evaluate the reliability and credibility of expert testimony.”
Justice Elena Kagan wrote in the foreword to the manual that it was intended as a dispassionate guide for judges dealing with complicated topics. “We live in an era of science and technology, with legal controversies reflecting that fact,” she wrote.
Ms. Wentz said her chapter acknowledged the scientific consensus that climate change is driven by the burning of fossil fuels and also recognized areas of uncertainty, particularly around the field of attribution science, the study of how much effect climate change may have had on individual storms.
Mr. McCuskey and his colleagues alleged that the chapter was biased and that its authors were proponents of using the judicial system to file lawsuits about climate change “to advance their preferred political objectives.” They took issue with the authors citing the Intergovernmental Panel on Climate Change, a body of experts convened by the United Nations that produces a comprehensive overview of climate science every few years.
They also faulted Ms. Wentz and Dr. Horton for not citing the people behind a Energy Department report that downplayed the dangers of global warming. That assessment, which has been condemned by dozens of scientists, has been used by the Trump administration to justify the repeal of one of the central legal underpinnings of climate regulations, a decision known as the “endangerment finding.” (The repeal is expected on Thursday.)
Ms. Wentz said the Energy Department report was “clearly a political document” that was not subject to peer review, in contrast to the I.P.C.C. reports, which go through extensive vetting involving researchers from around the world. “That report is so obviously flawed, incorporating it into an assessment of climate science would itself be an infusion of politics into the science,” she said.
Republicans have also criticized a separate training program, the Climate Judiciary Project of the Environmental Law Institute, a nonprofit group in Washington, for what they call bias. The group says it was formed in response to demand from judges seeing increasing references to climate science. Ms. Wentz said she had contributed one training module for that project but was not involved in the overall curriculum or leadership.
Karen Zraick covers legal affairs for the Climate desk and the courtroom clashes playing out over climate and environmental policy.
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