In the Toolkit --


  • Guide to the Toolkit
  • Leagues in Action
  • I. Choosing a Role for Your League

    II. Grassroots Action Priorities

  • Climate Action
  • Price on Carbon
  • Our Children's Trust
  • Energy Efficient Buildings
  • Renewable Energy
  • Adapting to Climate Change
  • III. Basics of Climate Change

    IV. Engaging Individuals

  • Communicating About Climate Change
  • Preparing for a Meeting on Climate Change
  • Engaging Groups in Your Community
  • V. Promoting Public Policy

  • Community Action Models
  • Organizing For Community Action
  • Tips for Building Grassroots Support
  • League Action on Climate Change
  • International Action
  • VI. Resources


    In April 2007, the U.S. Supreme Court ruled (in Massachusetts v. EPA) that carbon dioxide and other greenhouse gases (GHGs) meet the definition of "air pollutants" under the Clean Air Act (CAA). The Court directed the Environmental Protection Agency (EPA) to determine whether GHG emissions endanger the public health or welfare -- or whether the science is too uncertain to make a reasonable judgment.

    In 2009, EPA conducted an extensive review of the scientific evidence and concluded that GHG emissions do threaten the public health and welfare of current and future generations. In addition to this "endangerment finding," EPA made a "cause and contribute finding" that GHG emissions from motor vehicles (the sector cited in the lawsuit) contribute to the atmospheric concentrations of these gases and thus to the threat from climate change.

    Motor vehicles. Once EPA issued its findings, it was required under the CAA to regulate GHG emissions from motor vehicles. The agency partnered with the Department of Transportation to set increasingly stringent standards for GHG emissions and fuel efficiency for motor vehicles: in 2010, for light-duty motor vehicles, model years 2012-2016; in 2011, for heavy-duty trucks and buses, model years 2014-2018; and in 2012, for light-duty vehicles, model years 2017-2025. (A more detailed history of EPA motor vehicle regulations is here.)

    Large stationary sources. Once EPA finalized emission standards for light-duty motor vehicles in 2010, the agency began developing regulations for large stationary sources of GHG emissions. EPA issued rules incorporating GHGs into the permitting process for new power plants and other large stationary sources and has now finalized performance standards (i.e., the Clean Power Plan) for existing and new power plants. EPA has also issued rules limiting emissions of mercury and other toxic pollutants, a rule to address the problem of cross-state pollution from power plants, and air quality standards for soot and other fine particulate matter. (A more detailed history of EPA regulations of large stationary sources is here.)

    Learn more about --

    Last updated: 8/7/2015