The newly revised Reference Manual on Scientific Evidence (Fourth Edition) (“RMSE”), a vital resource used by federal judges to understand complex technical issues, was released at the end of 2025. The RMSE is an indispensable tool that can strengthen defense lawyers’ Rule 702 arguments and play an important role in keeping “junk science” out of the courtroom.

Added to the Fourth Edition was a new, 80-page “Reference Guide on Climate Science” intended to help judges navigate the growing number of climate-related lawsuits by explaining how specific weather events or impacts can be linked to human-caused emissions. The article was well researched and highly instructive. It came as a shock to federal court litigators that the Federal Judicial Center (FJC) unceremoniously deleted the entire climate science chapter on February 6, 2026, a few days after a coalition of 27 Republican state attorneys general sent a letter to the FJC demanding the chapter’s immediate removal. The Republican state attorneys argued that the climate science discussion was biased and threatened to undermine judicial impartiality. They argued that the chapter was “indoctrinating” judges with “left-wing prose.” Further, they (and Republican members of Congress) criticized the authors for relying on consensus-based bodies like the UN’s Intergovernmental Panel on Climate Change (IPCC) while ignoring a highly controversial 2025 Department of Energy report that was skeptical of climate science.

The removal sparked a massive outcry from the scientific and legal communities. Over two dozen of the manual’s co-authors and various scientific organizations (including the American Meteorological Society and the American Statistical Association) condemned the move as a “political attack” on the independence of the judiciary. The scientists argued that the chapter had undergone rigorous peer review and that removing it deprived judges of a “baseline explanation” of the science, leaving them vulnerable to “cherry-picked” data presented by paid expert witnesses in court.

Some legal experts pointed out the inconsistency in the FJC’s logic. The manual contains chapters on other “litigation-heavy” topics like Asbestos, DNA Evidence, and Epidemiology. Judges noted that those chapters were not removed despite being central to massive, high-stakes lawsuits, leading to the conclusion that the climate chapter was singled out solely for political reasons.

The administrative quiet of the FJC’s decision was quickly shattered by a chorus of high-profile dissenters. Leading the charge was Nancy Gertner, a retired judge of the U.S. District Court for the District of Massachusetts and current Harvard Law senior lecturer. Gertner called the removal “outrageous.” In her view, the FJC’s move signaled a dangerous vulnerability to the “politics of the time.” She likened the attorneys general demands for “balance” to a false equivalence, stating:

“It’s like we’re at a time that somehow we think we have to give equal time to the people who believe that the Earth is flat. I mean, you don’t. There are certain issues that are simply beyond the pale.”

For Gertner and other jurists, the manual isn’t supposed to be a debate stage; it’s supposed to be an independent anchor. Judges use the manual to understand the broader scientific landscape so they can better evaluate—and sometimes “supplant”—the arguments being fed to them by lawyers. Scholars have pointed out that while the attorneys general attacked the authors’ affiliations, the chapter underwent the same rigorous, multi-layered peer review as the sections on DNA or Epidemiology.

For their part, the attorneys general coalition relied on a controversial 2015 report from DOE in support of their claim that climate science is “hotly disputed.” This report, the coalition argued, was the “missing link” that the FJC manual ignored. However, as it turns out, the report itself was the product of a “Secret Panel” of scientists whose identities and funding were shielded from public view until a series of FOIA requests blew the lid off the operation. The “Secret Panel” responsible for the DOE’s report’s authorship was composed of researchers with ties to fringe think tanks, who operated outside the standard National Academies peer-review process. When the DOE report was finally scrutinized by the broader scientific community in early 2026, the consensus was that the DOE panel ignored fifty years of satellite data in favor of a narrow window of atmospheric readings from the mid-90s to support their findings. Moreover, leaked emails suggested that the report’s executive summary was edited not by climatologists, but by political appointees seeking to create “probative doubt” for use in active ongoing litigation.