In the absence of a coherent national policy to address global climate change, there was an emergence of new scales of environmental governance in the United States. They include regional initiatives that configure binding agreements between individual states within the United States that in some instances also involve cross-border collaborations with Canadian provinces. There are currently three such initiatives: the Northeastern Regional Greenhouse Gas Initiative, the Western Climate Initiative, and the Midwestern Regional Greenhouse Gas Reduction Accord. Combined, they include twenty-four states representing over half of the U.S. economy and four Canadian provinces representing almost three quarters of the Canadian economy. These initiatives are an interesting and unprecedented experiment in environmental governance. As such, they inform current conceptualizations of scale within human geography. They also evidence the need for geographers to enter into public debates on climate change governance and e...