Limiting anthropogenic climate change requires the stabilization of radiative forcing, a measure of the change in atmospheric energy balance by greenhouse gases (GHGs) and aerosols.1 This article explores the potential implications of stabilization for the USA within a global context. We explore the US implications within a cooperative global scenario in which radiative forcing from carbon dioxide (C 0 2), methane (CH4), nitrous oxide (NzO), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6) is limited to 3.4 W/m2, relative to a preindustrial state. This radiative forcing level is consistent with stabilizing the concentration of C 0 2, the most important GHG released by humans to the atmosphere, at approximately 450 parts per million (ppm), stabilizing the concentration of CH4 at approximately 1.4 ppm, and stabilizing the concentration of N20 at 0.36 ppm. There is no scientific consensus that limiting radiative forcing to 3.4 W/m2 is the 'right' target. Nevertheless, limits in this ränge are of particular interest from the perspective of the low-carbon society and are the subject of this series of papers in this Climate Policy Supplement.