Source: AGU Advances
In 2003, several states and environmental groups sued the U.S. EPA for violating the Clean Air Act by not regulating emissions from new vehicles.
When the case eventually reached the Supreme Court, a group of climate scientists contributed an amicus brief—a legal document in which a third party not directly involved in the case can offer testimony—sharing data demonstrating that rising global temperatures were directly caused by human activity. This led to the Supreme Court deciding that greenhouse gases did constitute pollutants under the Clean Air Act and, ultimately, to the EPA’s 2009 endangerment finding that greenhouse gas emissions endanger human health. The endangerment finding became the basis for governmental regulation of greenhouse gases. Sixteen years later, the Trump administration is poised to repeal it, along with other environmental protections.
In a new commentary, Saleska et al., the authors of the amicus brief, reflect on the brief and the damage the endangerment finding’s potential repeal could cause.
Today, many of the climate scientists’ concerns from the early 2000s have become reality, the authors say. The Earth’s 12 warmest years on record all occurred after 2009. The oceans are growing hotter and more acidic, and Arctic sea ice is retreating. Sea level rise is speeding up—from 2.1 millimeters per year between 1993 and 2003 to 4.3 millimeters per year between 2013 and 2023. Continued warming is also affecting human health. Direct heat-related deaths are on the rise, and so too are wildfires, precipitation extremes such as flooding and drought, climate-enabled spread of disease, and disruptions in agricultural productivity.
The amicus brief authors also note that attribution science, the field that links specific weather events to climate change, has advanced since 2009. Today, they are even more firm in their stance that climate change poses a serious threat to society.
A reversal of the endangerment finding would likely require a lengthy legal process and compelling evidence that climate change does not pose a risk to human health and well-being. But the possibility of a repeal implies a worrying lack of trust in the science and increasing politicalization surrounding climate issues, the authors say. If the role of climate science in policymaking is weakened, it will harm scientific progress and our national well-being, they warn. (AGU Advances, https://doi.org/10.1029/2025AV001808, 2025)
—Rebecca Owen (@beccapox.bsky.social), Science Writer
