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EPA to Regulate Greenhouse Gas Emissions Under the Clean Air Act

The United States Environmental Protection Agency is moving forward in regulating greenhouse gas emission in the US from both mobile sources (principally autos and trucks) and stationary sources (industrial and power generation sources). The actions taken today support EPA in regulating greenhouse gas emissions under the Clean Air Act.

[Yesterday], the US EPA Administrator signed two distinct findings regarding greenhouse gases under section 202(a) of the Clean Air Act:

  • Endangerment Finding: The Administrator finds that the current and projected concentrations of the six key well-mixed greenhouse gases — carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) — in the atmosphere threaten the public health and welfare of current and future generations.
  • Cause or Contribute Finding: The Administrator finds that the combined emissions of these well-mixed greenhouse gases from new motor vehicles and new motor vehicle engines contribute to the greenhouse gas pollution which threatens public health and welfare.

These findings do not themselves impose any requirements on industry or other entities. However, this action is a prerequisite to finalizing the EPA’s proposed greenhouse gas emission standards for light-duty vehicles, which were jointly proposed by EPA and the Department of Transportation’s National Highway Safety Administration on September 15, 2009.


On April 2, 2007, in Massachusetts v. EPA, 549 U.S. 497 (2007), the Supreme Court found that greenhouse gases are air pollutants covered by the Clean Air Act. The Court held that the Administrator must determine whether or not emissions of greenhouse gases from new motor vehicles cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare, or whether the science is too uncertain to make a reasoned decision.

In making these decisions, the Administrator is required to follow the language of section 202(a) of the Clean Air Act. The Supreme Court decision resulted from a petition for rulemaking under section 202(a) filed by more than a dozen environmental, renewable energy, and other organizations.

On April 17, 2009, the Administrator signed proposed endangerment and cause or contribute findings for greenhouse gases under Section 202(a) of the Clean Air Act. EPA held a 60-day public comment period, which ended June 23, 2009, and received over 380,000 public comments. These included both written comments as well as testimony at two public hearings in Arlington, Virginia and Seattle, Washington. EPA carefully reviewed, considered, and incorporated public comments and has now issued these final


The key effects that support EPA’s determination that greenhouse gases in the atmosphere endanger the welfare of current and future generations include:

Sea Level Rise

  • The global sea level gradually rose in the 20th century and continues to rise.
  • The most serious potential adverse effects are the increased risk of storm surge and flooding in coastal areas from sea level rise and more intense storms. Observed sea level rise is already increasing the risk of storm surge and flooding in some coastal areas.
  • The U.S. East Coast and Gulf Coast are particularly vulnerable to sea level rise because the land is relatively low with respect to mean sea level and also is sinking in many places.

Water and Implications for Water Use

  • Rising temperatures will decrease the size of snow packs in the western United States, affecting seasonal water supplies, relied on by humans and wildlife .
  • Climate change will likely put more pressure on already stressed water resources in some areas of the United States.

Agriculture and Forestry

  • There is a potential for a net benefit in the near term for certain crops, but there is significant uncertainty about whether this benefit will last given the potential adverse impacts of climate change on crop yield, such as the increasing risk of extreme  weather events. Other aspects of this sector may be adversely affected by climate change, including livestock management and irrigation requirements, and there is a risk of adverse effect on a large segment of the total crop market.
  • Climate change has very likely already increased the size and number of wildfires, insect outbreaks, and tree mortality in the interior West, the Southwest, and Alaska, and will continue to do so.

Energy and Infrastructure

  • Climate change is likely to affect U.S. energy use (e.g., heating and cooling requirements), energy production (e.g., effects on hydropower), physical infrastructures, and institutional infrastructures.


  • Changes in climate will cause some species to shift north and to higher elevations, which may fundamentally rearrange U.S. ecosystems, and in combination with other stresses such as development, habitat fragmentation, invasive species, could have negative consequences on biodiversity and the benefits that healthy ecosystems provide to humans and the environment.
  • Climate change effects outside of the United States may exacerbate problems that raise humanitarian, trade, and national security issues for the Unite.

For more information, visit the EPA.

Article appearing courtesy of ENN