	Introduction

The scientific, economic, and political questions surrounding climate change have long been with us. This report focuses instead on a relative newcomer: the legal debate. Though the first court decision related to climate change appeared 19 years ago, the quantity of such litigation has mushroomed in recent years. Representatives of some suing organizations and states acknowledge that a prime cause for this litigation surge is the inaction of Congress and the executive branch during the George W. Bush Administration with regard to mandatory constraints on greenhouse gas (GHG) emissions, and their perception that litigation might help to prompt such action. The principal court cases, decided and pending, arise in eight contexts—a number that continues to grow. First and most important is the Clean Air Act (CAA). In April, 2007, the Supreme Court held in Massachusetts v. EPA that the U.S. Environmental Protection Agency (EPA) has authority under the CAA to regulate greenhouse gas emissions from new motor vehicles. The second context for climate change litigation is the federal wildlife statutes, raising the issue of whether statutes like the Endangered Species Act can be used to limit GHG emissions based on their contribution to climate-climate-related alterations of wildlife habitat. Fifth is common law tort theories such as nuisance and whether they be used successfully by state and private plaintiffs to force cutbacks in GHG emissions, or payment of damages? Seventh, chiefly with respect to coal-fired power plants, is state utilities laws. And eighth is whether general liability insurance policies cover harms and liabilities caused by climate change. One has ruled. As to the state of climate change science, the Court's focus on the policy reasons EPA gave as part of exercising its "judgment" obscures the fact that the agency's rejection of the petition stemmed in part from expressions of scientific uncertainty in a 2001 National Research Council report on the science of climate change. An appeal has been filed. National Environmental Policy Act

The National Environmental Policy Act (NEPA) cases involving climate change represent the oldest and most numerous category of climate change litigation. Three are on appeal, however. Federal Preemption

		Stationary Sources of GHG Emissions

The question of whether federal law preempts state regulation of GHG emissions arises chiefly in connection with mobile sources. An appeal in this case is pending as well. In a string of 2007 decisions under the Clean Air Act, Energy Policy and Conservation Act of 1975, foreign policy authority of the United States, and NEPA, courts have shown increased willingness to authorize or require government consideration of climate change.
The scientific, economic, and political questions surrounding climate change have long been with us. This report focuses instead on a relative newcomer: the legal debate. Though the first court decision related to climate change appeared 19 years ago, such litigation has proliferated in just the past six. Representatives of some suing organizations and states acknowledge that a prime cause for this litigation surge was inaction by Congress and the executive branch during the George W. Bush Administration with regard to mandatory constraints on greenhouse gas (GHG) emissions.
The court cases, decided and pending, arise in eight contexts. The first is the Clean Air Act (CAA). In Massachusetts v. EPA, the Supreme Court held that as to mobile sources of emissions (cars, trucks), the U.S. Environmental Protection Agency (EPA) has authority under the act to regulate greenhouse gas (GHG) emissions. This decision puts pressure on EPA to move forward as well with regulation of GHGs from stationary sources (power plants, factories).
Second, litigation under wildlife statutes, particularly the Endangered Species Act, raises the possibility that the impacts of climate change on wildlife may constrain private activities that emit GHGs.
Third, energy statutes have been invoked. It has been held, for example, that under the Energy Policy and Conservation Act, the United States must monetize the benefits of reduced carbon emissions as part of setting light-truck fuel economy standards.
Fourth, various statutes requiring federal government analysis and information dissemination—the National Environmental Policy Act (NEPA), Global Change Research Act (GCRA), and Freedom of Information Act (FOIA)—have generated climate-change litigation. NEPA suits make up the most numerous subset of this category. Courts agree that if a plaintiff can establish standing, NEPA can be used to compel agency consideration of the climate change effects of its actions.
Fifth, common law tort theories such as nuisance have been invoked, not yet successfully, to force cutbacks in GHG emissions, or payment of damages. Several cases are on appeal.
Sixth are the preemption suits. These challenge state regulation of GHG emissions from motor vehicles as preempted by the federal corporate average fuel economy standards or federal authority over foreign policy. The two rulings thus far have rejected these challenges, but are on appeal. California's suit attacking EPA's denial of its request for a waiver of federal preemption under the Clean Air Act has now been stayed, pending EPA reconsideration of the denial.
Seventh, chiefly with respect to coal-fired power plants, are suits under state utilities laws.
And eighth, one case asks whether existing general liability insurance policies cover climate-change-related liability.
Finally, the report discusses international law aspects of a nation's contributions to climate change, and offers some overview comments.