In the United States to date, most of the first genuine steps toward addressing the challenge of climate change have taken place at the state level.1 Many states have proceeded in a meaningful, comprehensive fashion while the federal government struggles to take its first significant step toward legislative or regulatory action. Yet it is clear that these state actions, even when taken together, are not enough to put the United States on a course to reduce greenhouse gas (GHG) emissions to the level deemed necessary by the science. Nationwide action requiring reductions in all 50 states will be necessary. Assuming the federal government will eventually put such a comprehensive program in place, however, a number of questions arise as to the appropriate division of responsibilities between state and federal governments across the many areas where climate change action is needed.

Given the relative historical competencies of state and federal governments, it is neither desirable nor likely that the federal government will step in comprehensively to eliminate any state role in tackling climate change. Indeed, some areas central to climate change policy, such as smart growth and land use planning, fall within the near-exclusive purview of state and local governments. At the other extreme are international climate change negotiations leading to international agreements, which is a matter for exclusive federal control. Most areas relevant to climate change policy, however, fall between these two extremes and have historically been shared by both state and federal governments.

Against the current and historical jurisdictional backdrop, the key question is not whether responsibility for climate change action should rest exclusively with the federal government or the states, but rather how the federal government and the states should share responsibility for tackling the problem. It is difficult to imagine the federal government stepping in to assume exclusive and broad authority over all activities in the United States that contribute to climate change. Because legal authority is already shared in many of these areas, the appropriate questions relate to the degree to which state and federal governments will continue to share responsibility. Will the path forward rely most heavily on the states to tackle the problem, with the federal government stepping in to make sure all states are acting with comparable vigor? Or will future climate change policy place the federal government in the dual role of both devising and implementing policy from Washington, D.C., perhaps with the states acting as local enforcers? Or will Congress devise an approach that places certain key responsibilities with federal agencies while vesting other key responsibilities with the states?

This paper aims to further a constructive dialogue on the appropriate roles for state and federal government in meeting the challenge of climate change in the United States. Section II includes a brief overview of the climate change actions taken by states, a review of the common issues that have arisen in the debate over state action, and a brief exposition of the relevant historical areas of federal and state authority. Section III summarizes the law of federal preemption to provide a basic understanding of the various way state policy can be affected by federal action. Section IV briefly explores the state and federal partnership established under the federal Clean Air Act for reducing air pollution, noting some key experiences with the Clean Air Act as it relates to the division of federal and state responsibility. Section V examines three possible approaches to comprehensive nationwide climate change action, taking into account the challenges and benefits associated with each option. Section VI sets out some key conclusions, questions, and principles for a continuing dialogue on these issues.In the United States to date, states have taken most of the significant actions to address climate change. Yet enactment of a nationwide program requiring reductions across the entire United States is both necessary and increasingly likely. This prospect raises a number of questions as to the appropriate division of responsibilities between state and federal governments across the many areas where climate change action is needed. The key question is not whether responsibility for climate change action should rest exclusively with the federal government or the states, but rather how and to what degree the federal government and the states should share responsibility for tackling the problem.

A number of arguments exist to support state-level action on climate change. States have historically played a role as effective first-movers on important environmental issues, functioning as policy innovators, testing policies that have later been adopted at the federal level. States also bring an understanding of the unique circumstances within their boundaries and a familiarity with their stakeholders. States drive federal action, sometimes insisting that policies be strengthened even after the federal government has acted.

There are also numerous arguments in favor of a strong federal role in climate policy. A federal program would bring every state into the climate change effort and tend to level the playing field for businesses in all 50 states. Federal action offers a platform for engaging with other nations in forging an international emissions reduction agreement. A national GHG cap-and-trade program would keep costs manageable and drive climatefriendly technological innovation, and could link with other markets around the world.

Given the strong reasons for both state and federal action on climate change, it is perhaps not surprising that historically state and federal governments have chosen to share authority over most areas where climate change action is needed. This is true across most air pollution control, energy supply, energy efficiency, transportation, forestry and agricultural policy areas. Rather than asking whether federal or state government is best able to address climate change, the more relevant question is which level of government should tackle which parts of the challenge.

Precisely how to delineate state and federal roles in a comprehensive nationwide climate change program should be the focus of a constructive national dialogue. This paper evaluates several possible approaches along a continuum from heavy reliance on federal action to heavy reliance on state action. The scenarios examined differ in the degree to which responsibility for reductions is shared between federal and state governments, but each recognizes that some action will be required at both levels.

Federal action on climate change is needed to achieve the significant reductions science demands and to establish a minimum level of uniformity across the U.S. economy. This federal action can preserve room for states to continue in their important roles as policy innovators, on-the-ground implementers, and policy drivers, and to capitalize on the significant experience in the states across the many aspects of climate change action. A federal climate change program will be most successful if it is designed with the relative strengths of each level of government in mind.