Radiative forcing calculations for CH{sub 3}Br

Abstract

Methyl Bromide, CH3Br, is the major organobromine species in the lower atmosphere and is a primary source of bromine in the stratosphere. It has a lifetime of 1.3 years. The J R methyl bromide spectra in the atmospheric window region, 7 -13p, was determined using a well tested Coriolis resonance and &doubling (and E -resonance) computational system. A radiative forcing value of 0.00493 W/m2/ppbv was obtained for CH3Br and is approximately linear in the background abundance. This value is about 2 percent of the forcing of CFC-11 and about 278 times the forcing of C02, on a per molecule basis. The radiative forcing calculation is used to estimate the global warming potential (GWP) of CH3Br. The results give GWPs for CH3Br of the order 01 13 for an integration period of 20 years and 4 for an integration period of 100 years (assuming C02 = 1, following IPCC 119941). While CH3Br has a GWP which is approximately 25 percent of the GWP of C Q , the current emission rates are too low to cause serious atmospheric greenhouse heating effects at this time.