Regional air pollution and global climate change are separate environmental problems, but their causes and solutions are closely linked. By crafting smart policies that recognize the multiple benefits--so called co-benefits or co-control benefits--of actions that reduce both air pollution and greenhouse gas emissions, state and local governments can achieve a wide range of environmental, public health, and economic goals efficiently. The burning of fossil fuels results in the emissions of greenhouse gases and air pollutants that cause problems like acid rain and smog. When fossil fuels are used more efficiently, or when they are replaced by non-fossil energy sources such as solar or wind power, both air pollution and greenhouse gas emissions may be reduced. Extraction and processing of fossil fuels also result in discharges of water pollutants and generation of solid wastes. So policies and programs that cut emissions of greenhouse gases by reducing fossil energy use not only limit long-term global climate change, but also reduce air pollution, improve the quality of air and water, and reduce risks to human health.