National Academies Publish New Report Reviewing Evidence for Greenhouse Gas Emissions and U.S. Climate, Health, and Welfare

News Release | September 17, 2025

WASHINGTON — A new report from the National Academies of Sciences, Engineering, and Medicine says the evidence for current and future harm to human health and welfare created by human-caused greenhouse gases is beyond scientific dispute.

The report focuses on evidence gathered by the scientific community since 2009, when the U.S. Environmental Protection Agency found that greenhouse gas emissions threaten public health and welfare. The EPA recently gave notice of proposed rulemaking indicating its intention to rescind this finding.

The report says EPA’s 2009 finding was accurate, has stood the test of time, and is now reinforced by even stronger evidence. Much of the understanding of climate change that was uncertain or tentative in 2009 has now been resolved by scientific research, the report says.

“This study was undertaken with the ultimate aim of informing the EPA, following its call for public comments, as it considers the status of the endangerment finding,” said Shirley Tilghman, professor of molecular biology and public affairs, emeritus, and former president, Princeton University, and chair of the committee that wrote the report. “We are hopeful that the evidence summarized here shows the strong base of scientific evidence available to inform sound decision-making.”

To prepare its report, the committee considered widely available datasets that provide information about greenhouse gas emissions, the climate system, and human health and public welfare; a broad range of peer-reviewed literature and scientific assessments; and more than 200 comments submitted in response to a request for information.

The report concludes:

• Emissions of greenhouse gases (GHGs) from human activities are increasing the concentration of these gases in the atmosphere. Human activities, such as the extraction and burning of fossil fuels, cement and chemical production, deforestation, and agricultural activities, emit greenhouse gases, which include carbon dioxide, methane, nitrous oxide, and fluorinated gases, into the atmosphere. Total global GHG emissions continue to increase, even though U.S. emissions of CO2 have decreased slightly in recent years largely due to changes in energy production and consumption. Multiple lines of evidence show that greenhouse gas emissions from human activities are the primary driver of the observed long-term warming trend. No known natural drivers, such as incoming solar radiation or volcanic emissions, can explain observed changes.   

• Improved observations confirm unequivocally that greenhouse gas emissions are warming Earth’s surface and changing Earth’s climate. Longer records, improved and more robust observational networks, and analytical and methodological advances have strengthened detection of observed changes and their attribution to elevated levels of greenhouse gases. Trends observed include increases in hot extremes and extreme single-day precipitation events, declines in cold extremes, regional shifts in annual precipitation, warming of the Earth’s oceans, a decrease in ocean pH, rising sea levels, and an increase in wildfire severity.

• Human-caused emissions of greenhouse gases and resulting climate change harm the health of people in the United States. Climate change intensifies risks to humans from exposures to extreme heat, ground-level ozone, airborne particulate matter, extreme weather events, and airborne allergens, affecting incidence of cardiovascular, respiratory, and other diseases. Climate change has increased exposure to pollutants from wildfire smoke and dust, which has been linked to adverse health effects. The increasing severity of some extreme events has contributed to injury, illness, and death in affected communities. Health impacts related to climate-sensitive infectious diseases — such as those carried by insects and contaminated water — have increased. New evidence is developing about additional health impacts of climate change, including on mental health, nutrition, immune health, antimicrobial resistance, kidney disease, and negative pregnancy-related outcomes. Groups such as older adults, people with preexisting health conditions or multiple chronic diseases, and outdoor workers are disproportionately susceptible to climate-associated health effects. Even as non-climate factors, including adaptation measures, can help people cope with harmful impacts of climate change, they cannot remove the risk of harm. 

• Changes in climate resulting from human-caused emissions of greenhouse gases harm the welfare of people in the United States. Climate-driven changes in temperature and precipitation extremes and variability are leading to negative impacts on agricultural crops and livestock, even as technological and other changes have increased agricultural production. Climate change, including increases in climate variability and wildfires, is changing the composition and function of forest and grassland ecosystems. Climate-related changes in water availability and quality vary across regions in the United States with some regions showing a decline. Climate-related changes in the chemistry and the heat content of the ocean are having negative effects on calcifying organisms and contributing to increases in harmful algal blooms. U.S. energy systems, infrastructure, and many communities are experiencing increasing stress and costs owing to the effects of climate change. 

• Continued emissions of greenhouse gases from human activities will lead to more climate changes in the United States, with the severity of expected change increasing with every ton of greenhouse gases emitted. Despite successful efforts in many parts of the world to reduce emissions, total global greenhouse gas emissions have continued to increase, and additional warming is certain. All climate models — regardless of assumptions about future emissions scenarios or estimates of climate sensitivity — consistently project continued warming in response to future atmospheric GHG increases. Applying fundamental physics of the Earth system leads to the same conclusion. Continued changes in the climate increase the likelihood of passing thresholds in Earth systems that could trigger tipping points or other high-impact climate surprises.

The study — undertaken by the Committee on Anthropogenic Greenhouse Gases and U.S. Climate: Evidence and Impacts — was sponsored by the National Academy of Sciences Arthur L. Day Fund and the Ralph J. Cicerone and Carol M. Cicerone Endowment for NAS Missions. The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, engineering, and medicine. They operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln.

Contact:

Office of News and Public Information

202-334-2138; email news@nas.edu