IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group I: The Physical Science Basis Revised GWP Formulations Including the climate efficacy in the GWP

As discussed in Section 2.8.5, the climate efficacy can vary between different forcing agents (within 25% for most realistic RFs). Fuglestvedt et al. (2003) proposed a revised GWP concept that includes the efficacy of a forcing agent. Berntsen et al. (2005) calculated GWP values in this way for NOx and CO emissions in Europe and in South East Asia. The efficacies are less uncertain than climate sensitivities. However, Berntsen et al. (2005) showed that for ozone produced by NOx emissions the climate efficacies will also depend on the location of the emissions.