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In 2003, several states and environmental groups sued the U.S. EPA for violating the by not regulating emissions from new vehicles.

When the eventually reached the Supreme Court, a group of climate scientists —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 that greenhouse gases did constitute pollutants under the Clean Air Act and, ultimately, to the EPA's 2009 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 , along with .

In a new published in AGU Advances, Scott Saleska and colleagues, the authors of the amicus brief, reflect on the brief and the damage the endangerment finding's could cause.

Today, many of the climate scientists' concerns from the early 2000s have become reality, the authors say. Earth's 12 warmest years on record all occurred after 2009. The oceans are growing and , and Arctic sea ice is . 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 are on the rise, and so too are , precipitation extremes such as and , climate-enabled , and disruptions in .

The amicus brief authors also note that 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 politicization 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.