DEFENDING THE NATIONAL CLIMATE ASSESSMENT

Our resilience as a nation depends on our willingness to face reality head-on. For over three decades, the National Climate Assessment has drawn on the best available science to understand how climate change affects every region of the United States and every sector of the U.S. economy, helping us make smarter, more informed decisions.

First authorized by Congress in 1990, the Assessment was created to "produce information readily usable by policymakers" and to "increase understanding of and response to global change." This path-breaking legislation has guided decisions on everything from floodplain planning to wildfire response, infrastructure design, and public health readiness. The law requires that its findings be shared not only with Congress and the President, but also with the public at large.

The National Climate Assessment is a statutory obligation, enacted with broad bipartisan support and signed into law by President George H. W. Bush. Canceling the Assessment and turning away from science at a moment of escalating climate risk violates the executive’s constitutional duty to faithfully execute the laws of the land and obstructs public access to information required by law.

Halting this work is as shortsighted as it is unlawful. The Act itself makes clear that climate research is vital to “national economic well-being,” “public health and safety,” and “international cooperation.” Denying Americans this knowledge undermines the Constitution’s promise to “promote the general welfare” and “secure the blessings of liberty for future generations,” weakening our country’s ability to prepare for future challenges.

Since the legislation was passed in 1990:

• CO₂ levels have risen by 69 parts per million, a nearly 20% increase since 1990, reaching 418 ppm as of March 2025. That surpasses the widely recognized “red line” of 400 ppm, beyond which climate scientists warn of increasingly irreversible damage. Elevated greenhouse gas emissions like CO₂ drive greater radiative forcing, stronger climate feedback loops, and escalate the risks the National Climate Assessment was created to track, like extreme weather, rising seas, intensifying wildfires, and growing public health threats. Source
• The planet has warmed by approximately 0.9°C, meaning that over two-thirds of all warming since pre-industrial times has happened after the U.S. made a legal commitment to track and understand climate change through the Global Change Research Act. The world is heating faster, and the need for clear, science-based assessments has never been more urgent. Source
• Global sea levels have risen by about 10 centimeters since 1990, with the rate of rise more than doubling over that time. This acceleration increases the risk of flooding, infrastructure damage, and human displacement, precisely the kind of impact the National Climate Assessment was created to help communities prepare for. Source

We, the undersigned, believe it is necessary to offer the following evidence-based statements in light of recent efforts to cut funding, eliminate coordinating offices, and narrow the scope of the National Climate Assessment, actions that amount to a quiet cancellation of this important leadership initiative and critical public resource^*. The scientific and civic foundations laid by the Global Change Research Act of 1990 charged our nation with understanding and responding to climate change, which is now a defining threat to public health, national security, and long-term economic prosperity. As experts trained to evaluate trade-offs, costs, and consequences, we view the continued dismantling of this assessment as both economically shortsighted and deeply irresponsible.

• The National Climate Assessment continually updates and refines our understanding of climate risks, highlighting emerging threats and where projections have changed. For example, more recent assessments place less weight on extreme emissions scenarios like RCP 8.5 as the most likely outcome, helping decision-makers focus on the most plausible risk pathways. Source
• Economic growth and emissions reduction are not mutually exclusive. Forty-nine middle to high-income countries, including the U.S., have proven it’s possible to decouple growth from emissions. Source
• Failing to act on climate change comes at a steep cost. Leading research shows that ignoring climate change will cost far more in the long run. Without emissions reductions, U.S. GDP could fall by 4% by 2100, with a 5% chance of a 21% loss. Source. Other researchers estimate that 1% Celsius increase translates to 1.4% decrease in GDP. Source
• National security demands climate preparedness. The Department of Defense allocated $3.1 billion in FY 2023 for climate-related initiatives across four key areas: Installation Resilience, Operational Energy, Science and Technology, and Contingency Preparedness. This investment ensures U.S. forces can operate under increasingly volatile conditions and underscores that climate adaptation is mission-critical. Source
• The National Climate Assessment has provided estimates of the economic costs associated with climate change, including infrastructure damage and health-related expenses. For instance, weather-related disasters currently generate at least $150 billion per year in direct damages to the U.S., a figure projected to increase due to climate change. Source
• The National Climate Assessment uses evidence-based analysis to evaluate climate risks and policy responses. This includes evidence showing that carbon pricing can reduce emissions efficiently while supporting economic growth, and that the social cost of carbon is a scientifically grounded measure of the damages caused by greenhouse gas emissions. Source 1, Source 2
• Addressing climate risk requires interagency coordination. The National Climate Assessment exemplifies how agencies can work together to assess risks and share vital knowledge across sectors.
• Municipalities across the United States reference the National Climate Assessment data to improve disaster preparedness, helping emergency officials develop hazard mitigation strategies for hurricanes and extreme weather events. Without continued assessments, regions will face increased planning risks. Source
• The National Climate Assessment has documented health risks associated with climate change, such as increased heat-related illnesses and the spread of infectious diseases. This information has been crucial for public health officials in developing strategies to mitigate these risks, especially for vulnerable populations. Source
• The National Climate Assessment outlines key policy priorities, including investing in clean energy, boosting climate resilience for cities and towns, but also for agriculture, and addressing environmental justice.

• The National Climate Assessment is grounded in interdisciplinary collaboration, with economists playing a central role. Their expertise helps quantify climate damages, evaluate policy trade-offs, and ensure that responses are scientifically sound and economically efficient.

By signing this petition, we call for the immediate reinstatement of the authors and the on-time public release of the U.S. National Climate Assessment, in keeping with both the letter of the law and the urgency of this moment.

^* Update: as of June 30th, 2025 the five previous National Climate Assessments have been removed from U.S. Government websites. Older versions are archived through the National Oceanic and Atmospheric Administration.