In the absence of a federal climate change program, a number of states have taken actions that directly address greenhouse gases. States' efforts cover a wide range of policies, from outlining possible strategies to setting mandatory greenhouse gas emission standards. Although much of the early activity was largely symbolic, the more recent state actions have been more pragmatic. The states' motivations may be as diverse as the actions themselves. Some states are motivated by projections of climatic changes, while others view their policies as economic opportunities. States also point to the potential co-benefits of reducing greenhouse gases: improvements in air quality, traffic congestion, and energy security. Another driver behind state action is the possibility of catalyzing federal legislation. Most of the states have shown at least a basic interest in climate change issues. Forty-two states have conducted greenhouse gas inventories; 30 states have either completed or are in the process of preparing climate change action plans; 12 states have set statewide greenhouse gas targets. However, only a small number of states have implemented or are creating mandatory emission reduction programs. The most significant developments have come from California and from a group of states in the Northeast. The Regional Greenhouse Gas Initiative (RGGI), a partnership of seven northeastern states, sets up a cap-and-trade system aimed at limiting carbon dioxide emissions from power plants. This is scheduled to take effect in 2009. California has made several notable steps. In 2004, the state issued regulations to reduce greenhouse gases from motor vehicles. Ten other states have formally adopted California's new vehicle requirements. In 2006, California passed two milestone climate change statutes. The first would establish a state-wide cap on greenhouse gases. The second would effectively limit the use of coal-generated electricity in California. Predicting the precise
consequences of the state-led climate change actions is difficult. Some actions, particularly the recent California legislation, may impact energy markets to some degree. Many observers suggest that the quantity and range of state actions will catalyze federal activity. Industry stakeholders are especially concerned that the states will create a patchwork of climate change regulations across the nation. This prospect is causing some industry leaders to call for a federal climate change program. If Congress seeks to establish a federal program, the experiences and lessons learned in the states may be instructive. Although some states are taking aggressive action, their possible emission reductions may be offset by increased emissions in states without mandatory reduction requirements. This is perhaps the central limitation of state climate change programs in actually affecting total greenhouse gas emissions. Legal challenges represent another obstacle for state programs, particularly for the more aggressive, mandatory programs.