sions in the range of 17 percent below 2005 levels by the year 2020. Given the GHG emission projections discussed in the preceding section, it is clear that the United States will not be able to meet such a commitment without a significant departure from “business-as-usual.”

The federal government has adopted some policies (such as subsidies and tax credits) to catalyze the development and implementation of climate-friendly technologies, and there are also a range of voluntary federal programs in place to encourage energy efficiency and GHG emission reductions. More comprehensive federal-level legislation remains stalled. In June 2009, the House of Representatives passed the American Security and Clean Energy Act, which would have established a cap-and-trade system designed to lower U.S. GHG emissions by 17 percent by 2020 and 80 percent by 2050. A similar bill failed to reach the Senate floor, however; and following the 2010 mid-term elections, the prospects of any significant climate legislation being passed in the near future have diminished further.

In 2007 the U.S. Supreme Court instructed the U.S. Environmental Protection Agency (EPA) that it is required under the Clean Air Act to regulate emissions of CO2 and five other greenhouse gases if it finds that such emissions threaten the public health and welfare.9 In 2009 the EPA issued such a finding and, as a consequence, the EPA is currently developing regulations on GHG emissions from newly constructed or modified power plants and industrial sources;10 recently, together with the National Highway Traffic Safety Administration, it issued a coordinated set of fuel economy and GHG emissions standards for light-duty vehicles. However, there are many obstacles in the path to EPA regulation (including, for example, potential congressional legislation that would delay or rescind EPA’s authority, and litigation likely to follow rulemaking efforts that would use the judiciary to do the same). Thus the timing and character of regulatory programs to control GHG emissions are by no means certain.

Despite the current lack of comprehensive national policies, early actors at other levels of government and in the private sector are advancing policies and commitments to reduce emissions and lessen impacts. In the private sector, many corporations have made commitments or developed action plans for significantly reducing emissions from their operations.11 More than 1,000 mayors have signed onto the U.S. Conference of Mayors’ Climate Protection Agreement, pledging to reduce their city’s overall emissions by 7 percent below 1990 levels by 2012.12 A majority of states have adopted some form of renewable portfolio standard,13 energy efficiency program requirements, or emissions reduction goal, and some have adopted or plan to adopt cap and trade systems to reduce GHG emissions (for example, the Regional Greenhouse Gas Initiative of the northeastern U.S. states, the Western Climate Initiative, the Midwest-

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