In the absence of federal leadership to address climate change, many states and regions have begun taking action on their own. States are setting targets for reducing their greenhouse gas emissions, adopting policies to promote renewable energy and energy efficiency, and developing statewide climate action plans. At the regional level, states are coming together to launch emissions trading programs and support clean energy development. While confronting the challenge of climate change requires a national and international response, the states and regions have a valuable role to play in showing what works and in laying the groundwork for broader action.