Correct use of radiative efficiencies in calculating global warming potentials and other emission metrics

Abstract. The calculations of Global Warming Potentials (GWPs) and other related climate emission metrics should use radiative efficiencies that are representative of the mean atmospheric mole fraction, rather than the surface mole fraction as is commonly used. This correction leads to an upward revision of GWP values. Radiative forcing from projected changes in mean atmospheric mole fraction (such as for climate scenario) also need to be corrected. For species with lifetimes greater than a few years, the revision is an increase of a few percent e.g., 8 % for trichlorofluoromethane (CFC-11). For species with lifetimes less than a year this correction can lead to increases in the GWPs (and in some cases radiative forcing) of tens of percent, which could impact on policymaker decisions on the desirability of using such gases.