Because energy supplies and air pollution typically cross political and geographical boundaries, and implementing large-scale change can be expensive, a number of U.S. states have developed regional partnerships to address the issue of energy production and related greenhouse gas emissions. One such partnership is the landmark Regional Greenhouse Gas Initiative (RGGI). Launched by New York, RGGI is a multi-state greenhouse gas emissions cap-and-trade program involving Connecticut, Delaware, Maine, Massachusetts, New Hampshire, New Jersey, Rhode Island, Vermont, and Maryland. RGGI aims to stabilize greenhouse gas emissions from electricity generating power plants between 2009 and 2014, and to further reduce emissions 10% below 2009 levels by 2018.
Two other regional agreements addressing climate change are the Western Climate Initiative (WCI) and the Midwestern Greenhouse Gas Reduction Accord. The WCI was launched in 2007 and includes seven western states and two Canadian provinces. The Midwestern Greenhouse Gas Accord was signed in 2007 by the governors of six states and one Canadian province.