• Reduce concentrations of GHGs in the atmosphere as the principal means to limit the magnitude of climate change. This is primarily a challenge of reducing net GHG emissions (directly, or possibly through enhanced sequestration), but it could also encompass strategies to remove GHGs directly from the atmosphere.

  • Promote options and policies that appear to be technically and economically feasible now or could become feasible in the near term. However, the report also identifies other strategies that may play an important role in the future but whose potential cannot be reliably estimated, and we encourage policies that can be adopted now to accelerate these future innovations.

Although the urgent need for action is real, many relevant efforts are already under way. For example, 24 U.S. states and more than 1,000 U.S. cities have adopted some form of targets for limiting GHG emissions. The judicial system is also playing an increasingly important role, and two recent lawsuits may result in GHG emissions reduction through administrative or judicial action. As a result of Massachusetts v. EPA, the Environmental Protection Agency has issued a finding under the Clean Air Act that GHGs are endangering public health and welfare, which may form the basis for extensive regulation of GHGs under the Act. In Connecticut v. American Electric Power, the Second Circuit allowed a public nuisance case by several states and nonprofit organizations to go forward against the country’s largest utilities, alleging that past and ongoing CO2 emissions are contributing to global warming. If the plaintiffs ultimately succeed, the defendants presumably could be required to reduce their emissions. Furthermore, during the course of this study, Congress and the Obama Administration have been considering legislation to establish a national program for limiting future climate change.

It is not our intent to comment on these actions or to evaluate the policies they embrace. Rather, we regard them as the necessary beginning of an ongoing process of developing a coherent national policy for limiting future climate change. Although we are optimistic that the United States can meet the challenges associated with limiting future climate change, we are also convinced that this can only be done as a long-term evolving process. Accordingly, our study develops two major themes in addition to the need for urgent action:

  • Provide a national framework of strategies and policies to limit climate change, now and in the future. National policy goals must be implemented through the actions of the private sector, other levels of government, and individuals. The role of the federal government is to provide strong leadership and help shape the landscape in which all of these actors make decisions. Although this report

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