For 15 years, the American judiciary waited for an updated roadmap through the thicket of modern science. Yet within five weeks of its publication, the guide’s newest and most fiercely contested section was erased.
On Dec. 31, 2025, the Federal Judicial Center and the National Academies of Sciences, Engineering, and Medicine released the long-anticipated fourth edition of the Reference Manual on Scientific Evidence, a treatise judges use as evidentiary gatekeepers. For the first time, the manual included a peer-reviewed guide spanning more than 90 pages on climate science, detailing consensus methodologies, climate modeling and extreme-event attribution.
By Feb. 6, following a push by Republican state attorneys general who said the information was biased and partisan, the FJC excised the entire section.
More recently, NASEM followed by pulling the guide from its public platform pending an independent process review.
Colorado legal observers watching climate dockets expand across the Tenth Circuit and state courts have been surprised by the swift capitulation. Mike Angstadt, an environmental law scholar and associate professor at Colorado College who studies climate governance and judicial decision-making, said, “While it was unfortunate to see judges lose what might have represented a timely and nonpartisan resource, it also validated the increasing intersection between our courts and the politics and scientific reality of climate change.”
Turning the Clock Back on Courtroom Debate
The timing of the handbook’s release and the cut of the climate guide come at a volatile moment. Across the country, judges are grappling with high-stakes municipal lawsuits targeting fossil fuel producers, constitutional challenges asserting public trust violations and administrative disputes over federal energy policy.
Depriving the bench of an authoritative scientific baseline, Angstadt warned, threatens to turn courtroom debate away from legal remedies and back to litigating basic facts.
He said, “This change could certainly affect emphases during litigation, preserving debate over what we should understand as comprising climatic reality, rather than moving toward consideration of whether and how the law should engage climate change.”
He continued, “Access to justice considerations could follow, too, as not all parties have equal resources to retain experts or specialized counsel to interpret science in this manner.”
The stakes are not confined to a group of cases, such as those that deal with emissions.
“Alongside the more than 2,000 U.S. cases that explicitly contain climate-related claims, it’s increasingly challenging to identify an area of law that isn’t, or won’t soon be, inflected by climate change,” Angstadt said. “Some areas of litigation, including natural resources and administrative law, connect clearly and currently to climate challenges. Sadly, though, it’s easy to imagine connections to climate change arising in a host of other issue areas, too, including human rights and finance.”
A Strain on Common-Law Traditions
Of course, judges are trained to dissect legal precedent, statutory interpretation and procedural rules, not atmospheric physics or carbon accounting. This knowledge gap was the impetus for FJC first commissioning the manual in 1994. Angstadt said the ability of judges “to keep pace with novel scientific methods and insights and to understand what science can and cannot tell us demands access not only to science itself but also to support for interpreting it.”
He also believes excising climate change from the manual strikes at the architecture of American jurisprudence. “Climate change is asking the law to do something fundamentally new,” he said. Whereas “much of law seeks to remediate known past harms or to examine historical baselines,” he said, “climate change challenges our courts to address future harms and to thoughtfully engage with uncertainty. It’s vitally important that judges have access to accurate, current, and unbiased information when doing so.”
Science versus Politics in Judicial Education
To those who contend that a judicial handbook should avoid topics entangled in policy disputes, Angstadt offered two counterarguments.
First, he said, “it would be difficult, if not impossible, to identify any area of the science-law interface that doesn’t engage in evolving or contested science or policy.” Two current examples in the manual are sections that address artificial intelligence and mental health.
Second, he noted the difference between political controversy and scientific controversy: “There’s overwhelming consensus among scientists about what climate change could mean, how it can be measured and what important areas of uncertainty remain and demand further research.”
The View from Colorado
For practitioners and judges in the West, the gap in judicial guidance hits particularly close to home.
“The issue of climate change is certainly very resonant here in Colorado, where we’re surrounded by finite water resources, contested public lands, mineral resources and natural hazards that will only intensify under climatic pressures,” Angstadt said.
But he emphasized that judges throughout the United States, and not just the Mountain West, are encountering climate litigation, now without institutional guidance, as in the case of Suncor Energy Inc. v. County Commissioners of Boulder County, scheduled for oral arguments before the Supreme Court on Oct. 5.
How courts bridge a knowledge deficit will remain a challenge. Angstadt noted that Colorado has long adapted institutional structures to handle technical subjects, most notably through specialized water courts where hydrological expertise concentrates.
He said, “We’re expecting our judges to do an awful lot, but that our society could more intentionally consider what supports could help judges to meet this mandate.”