Given the far-reaching nature of the climate challenge, effective federal policy is needed to achieve deep, long-term reductions in U.S. greenhouse gas emissions, and to help strengthen climate resilience across the U.S. economy. Even in the absence of a comprehensive federal approach, the federal government can help accelerate progress being made by cities, states, and companies. Federal policymakers have a number of policy tools at their disposal:

• Government research and development programs, such as the Advanced Research Project Agency-Energy, can drive progress in clean energy technologies and bring them to commercial use.
• Voluntary programs, like the Natural Gas STAR program, work with businesses to reduce emissions, often with public recognition.
• Traditional regulations, such as fuel efficiency and emissions standards for cars and trucks, require companies to increase energy efficiency or reduce emissions in their own operations or in the goods they produce.
• Market-based programs that put a price on carbon emissions, such as a carbon tax or cap-and-trade program, require emission reductions but let the private sector determine the most cost-effective way to achieve them.

While all these policies and programs can help reduce emissions and drive technological change, economists across the political spectrum agree that a flexible, market-based approach is the most cost-effective way to reduce emissions, and should be a centerpiece of a comprehensive climate strategy.

The legislative, executive, and judicial branches all have a role to play in reducing U.S. greenhouse gas emissions and building resilient communities.

Congress is responsible for authorizing laws to address the climate challenge and appropriating funding for relevant programs. The Clean Air Act, for instance, provides the foundation for many existing climate policies. An economy-wide, market-based approach to climate change would require Congress to enact new legislation. Congress also has an important role in oversight of the executive branch and ensuring the administration is implementing existing law.

The executive branch implements existing law through regulation and programs. These laws touch the work of nearly every federal agency. For example:

• The Clean Air Act requires the Environmental Protection Agency to work with states to reduce greenhouse gas emissions, including carbon dioxide and methane.
• Energy policy laws require the Department of Energy to partner with the private sector to research, develop, and deploy clean energy technologies, and to set energy efficiency standards for appliances and equipment.
• The Department of Transportation is required to set standards that improve the fuel economy of motor vehicles.
• The Department of Defense is required to plan for the global security consequences of climate change.

Many of the climate measures adopted by the Obama Administration are under review, and may be reversed, by the Trump Administration.

Federal courts interpret existing laws and provide a venue for states, industry and citizens to seek or challenge climate measures. A growing number of citizens and communities are bringing lawsuits seeking relief from the detrimental effects of increased carbon dioxide emissions. How the courts handle these cases will affect industry, government, law, policy, and the environment.