A Study of the Radiative Forcing and Global Warming Potentials of SF6

IPCC (2007) points out that the emission of sulphur hexafluoride (SF6) has been increasing greatly in recent years as part of the replacements for the Ozone Depleting Substances (ODSs). SF6 has been included in the Kyoto Protocol as one of the controlled man-made long-lifetime greenhouse gases. But there were few studies on its radiative forcing and global warming potentials and the absorption dataset used before also needs to be updated. In this work, the absorption cross sections of SF6 from the latest version of HITRAN2004 database are used. A radiation parameterization based on correlated k-distribution method for SF6 is developed, following the method of absorption coefficient rearrangement by Shi (1981), to calculate the radiative efficiency for clear sky and its global warming potentials. The global temperature potentials of SF6 are calculated here for the first time for the comparison with its global warming potentials. It is shown that the radiative efficiency of SF6 is 0.512 W/m2, which differs slightly from 0.506 W/m2 with the consideration of lifetime adjustment. According to the emission scenarios in IPCC (2007), the volume fraction of SF6 will be 35×10-12 to 70×10-12 in 2100, corresponding to the radiative forcing of 0.004 to 0.028 W/m2. For SF6, the 100-year global warming potential relative to CO2 is 2.33×104, which is 2.2% larger than that in IPCC (2007). The 100-year global temperature potential relative to CO2 for sustained emission is 2.26×104. The long-term influence of SF6 on global warming together with other man-made long-lifetime greenhouse gases should not be ignored.