Updated radiative forcing estimates of 65 halocarbons and nonmethane hydrocarbons

The direct radiative forcing of 65 chlorofluorocarbons, hydrochlorofluoroca rbons, hydrofluorocarbons, hydrofluoroethers, halons, iodoalkanes, chloroal kanes, bromoalkanes, perfluorocarbons and nonmethane hydrocarbons has been evaluated using a consistent set of infrared absorption cross sections. For the radiative transfer models, both line-by-line and random band model app roaches were employed for each gas. The line-by-line model was first valida ted against measurements taken by the Airborne Research Interferometer Eval uation System (ARIES) of the U.K. Meteorological Office; the computed spect rally integrated radiance of agreed to within 2% with experimental measurem ents. Three model atmospheres, derived from a three-dimensional climatology , were used in the radiative forcing calculations to more accurately repres ent hemispheric differences in water vapor, ozone concentrations, and cloud cover. Instantaneous, clear-sky radiative forcing values calculated by the line-by-line and band models were in close agreement. The band model value s were subsequently modified to ensure exact agreement with the line-by-lin e model values. Calibrated band model radiative forcing values, for atmosph eric profiles with clouds and using stratospheric adjustment, are reported and compared with previous literature values. Fourteen of the 65. molecules have forcings that differ by more than 15% from those in the World Meteoro logical Organization [1999] compilation. Eleven of the molecules have not b een reported previously.. The 65-molecule data set reported here is the mos t comprehensive and consistent database yet available to evaluate the relat ive impact of halocarbons and hydrocarbons on climate change.