Atmospheric lifetime and global warming potential of HFC-245fa

We describe the method used to compute the global warming potential of hydrofluorocarbon (HFC) 245fa (CHF2CH2CF3). The Atmospheric and Environmental Research (AER) two-dimensional (latitude-height) chemistry-transport model was used to calculate the atmospheric lifetime and atmospheric scale height of HFC-245fa. Assuming that reaction with OH is the only removal mechanism, the recommended rate constant from Jet Propulsion Laboratory [1997] (6.1 x 10(-13) exp (-1330/T) cm(3) s(-1)) implies a lifetime of 7.6 pears and an average atmospheric scale height of 35 km in the stratosphere. Using the IR absorption cross sections for HFC-245fa and CFC-11 determined in the laboratory, the AER one-dimensional radiative-convective model was used to calculate the radiative forcing, The value for HFC-245fa is 1.14 times larger than that for CFC-11 on a mass basis and 1.11 larger on a per molecule basis. The global warming potentials for HFC-245fa (relative to carbon dioxide) are 2400, 760, and 240 (based on the values for absolute global warming potential for carbon dioxide reported by Intergovernmental Panel on Climate Change [1996]) at integration time horizons of 20, 100, and 500 years, respectively.