Overview of EPA Endangerment Finding

Extensive scientific review found greenhouse gas pollution endangers public health

Date published: August 18, 2011

The Endangerment Finding fulfilled the Supreme Court's mandate.

In Massachusetts v. EPA (2007), the Supreme Court held that greenhouse gases are pollutants under the Clean Air Act.

The Court also rejected a "laundry list" of other reasons for inaction advanced by the Bush Administration as not consistent with the relevant provisions of Clean Air Act, which require regulation when EPA finds that emissions of a pollutant endanger public health or welfare.

On December 15, 2009, the Environmental Protection Agency (EPA) determined, based upon a careful review of the scientific record, that greenhouse gas emissions endanger the public health and welfare of current and future generations - an action that the D.C. Circuit resoundingly upheld in its June 26th ruling.

Research and public comment

The Endangerment Finding was made after an exhaustive review of climate change research and extensive public comment:

  • The Technical Support Document supporting the Endangerment Finding references more than 100 published scientific studies and considers peer-reviewed syntheses of climate change research by the U.S. Climate Change Science Program/U.S. Global Change Research Program, the Intergovernmental Panel on Climate Change (IPCC), and the National Research Council of the U.S. National Academy of Sciences.
  • The creation of these assessment reports involved hundreds of scientists who considered thousands of published studies on climate change, and the reports themselves were subject to extensive review by additional, independent experts.
  • EPA's thorough consideration of public input on the Endangerment Finding occupies eleven volumes and over 500 pages.

EPA findings

After this rigorous process, EPA made the following findings:

Humans generate climate pollution

Greenhouse gas pollution generated by human activity is causing climate change:

  • Heat-trapping greenhouse gases are now at record-high levels in the atmosphere compared to either the recent or distant past. Average global carbon dioxide (CO2) concentrations have increased approximately 38% since the Industrial Revolution, primarily due to human activities such as burning fossil fuels. Atmospheric concentrations of CO2 and methane are well above the natural range over at least the last 800,000 years.
  • Multiple lines of evidence indicate that the climate is changing due to rising concentrations of heat-trapping greenhouse gases, including long-term increases in global average air and ocean temperatures (with three independent worldwide datasets showing nearly identical warming trends), accelerated and expanded melting of snow and ice, acidification of the ocean due to CO2 absorption, changes in precipitation patterns and wildlife behavior, and rising global average sea level (because of melting ice sheets and the expansion of sea water with rising temperatures). Because greenhouse gases are long-lived in the atmosphere and because emissions will continue, warming and climate impacts during the 21st century are very likely to become more severe.
  • Most of the warming observed in the last 50 years is very likely due to human-caused greenhouse gas pollution, as variation in natural forces alone (such as solar and volcanic activity) cannot explain the observed warming—and would, in fact, have led to cooling.

A danger to public health

Greenhouse gas pollution will endanger public health:

  • The number and intensity of extremely hot days and heat waves will increase, increasing heat-related mortality and sickness. (Harmful heat-related impacts are expected to dominate benefits from reduced cold-related mortality and sickness.)
  • Regional ground-level ozone pollution (smog) will increase, escalating ozone-triggered respiratory illnesses and death.
  • The severity and/or frequency of extreme weather events such as storms (including hurricanes) will increase. The number of people at risk due to flooding will increase because of stronger precipitation events and the interaction of rising sea levels and stronger storm surges and hurricanes.

A danger to public welfare

Greenhouse gas pollution will endanger public welfare:

  • The number of people at risk due to droughts will increase because many low-rainfall areas are projected to receive less rain and because rising temperatures and evaporation will cause soils to dry.
  • Seasonal snowpacks in the Western United States will shrink, endangering water supplies relied upon by Western communities.
  • The number and extent of wildfires, insect outbreaks, and tree mortality in the interior West, the Southwest, and Alaska will likely expand.
  • Damaging impacts outside of the United States may harm our trade, humanitarian, and national security interests.

Support for EPA

Sixteen states (California, Connecticut, Delaware, Illinois, Iowa, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Mexico, New York, Oregon, Rhode Island, Vermont, and Washington) intervened to support EPA's climate protection as have Environmental Defense Fund and other allies.