A Study Of The Radiative Forcing And Global Warming Potentials Of HFCs, PFC And SF₆

IPCC (2007) points out that the emission of hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs) and Sulphur hexafluoride (SF₆) have been increasing greatly in recent years as replacements for the Ozone Depleting Substances (ODSs). They have been included in the Kyoto Protocol as the controlled man-made long-lifetime greenhouse gases. The radiative forcings and Global Warming Potentials (GWPs) of HFCs are studied all over the world, but the studies of PFCs have been in research for resent years. For SF₆, there were few studies on its radiative forcing and GWPs and the absorption dataset used before also needs to be updated. In this work, the absorption cross-sections of HFCs, PFCs and SF₆ from the latest version of HITRAN2004 database are used. Their new radiation parameterizations with different resolution (998 bands and 17 bands) based on correlated k-distribution method are developed following the method of absorption coefficient rearrangement by Shi (1981), to calculate their instantaneous radiative efficiency, stratospheric adjusted radiative efficiency and lifetime adjusted radiative efficiency for clear sky. The radiative forcings of HFCs, PFCs and SF₆ from 1750 to 2005 are calculated here as well as that from 2010 to 2100 in scenarios. The influences of different radiation schemes on radiative efficiency are discussed in this work. Then, their Global Warming Potentials (GWPs) and Global Temperature Potentials (GTPs) are calculated on the basis of their radiative efficiency and compared with each other, and the surface temperature changes due to different emissions of HFCs, PFCs and SF₆ are studied at last.It is shown in this work that for 17 bands radiation scheme, the radiative efficiencies of HFC-32, HFC-125, HFC-134, HFC-134a, HFC-143a and HFC-152a are 0.080, 0.107, 0.163, 0.117, 0.090 and 0.090 W m^-2ppbv^-1 respectively after the stratospheric adjustment and life-time adjustment. Their corresponding 100-year GWP relative to CO are 515, 1709, 1091, 1095, 3247 and 130 respectively and their corresponding 100-year GTP relative to CO₂ for sustain emission are 557, 1816, 1181, 1184, 3362 and 141 respectively. The total radiative forcing of HFCs here from 1750 to 2005 is about 0.0057 W m^-2, and will exceed 0.16 W m^-2 in 2100. The radiative efficiency of SF₆ is 0.512 W m^-2 ppbv^-1, which differs slightly from 0.506 W m^-2 ppbv^-1 with the consideration of lifetime adjustment. According to the emission scenarios in IPCC (2007), the abundance of SF₆ will be 35 to 70 pptv in 2100, corresponding to the radiative forcing of 0.004 to 0.028 W m^-2. For SF₆, the 100-year GWP relative to CO₂ is 23300, which is 2.2% larger than that in IPCC (2007). The 100-year GTP relative to CO₂ for sustain emission is 22588. For 998 bands radiation scheme, the radiative efficiencies of C₂F₆ and CF₄ are 0.453 and 0.119 W m^-2 ppbv^-1 respectively, which are little infected by the lifetime. The radiative forcings of C₂F₆ and CF₄ from 1750 to 2005 are 0.0013 and 0.0040 W m^-2 respectively, and will be 0.01 and 0.044 W m^-2 respectively in 2100 in scenario. The corresponding 100-year GWP relative to CO₂ of C₂F₆ and CF₄ are 22303 and 9225 respectively, and their corresponding 100-year GTP relative to CO₂ for sustain emission are 21601 and 8931 respectively. All of these results indicate that HFCs, PFCs and SF₆ have long-term influences on climate change, and they increase the global wanning with other greenhouse gases.