Atmospheric lifetime and global warming potential of HFC-245fa

We describe the method used to compute the global warming potential of hydr ofluorocarbon (HFC) 245fa (CHF2CH2CF3). The Atmospheric and Environmental R esearch (AER) two-dimensional (latitude-height) chemistry-transport model w as 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 labor atory, the AER one-dimensional radiative-convective model was used to calcu late the radiative forcing, The value for HFC-245fa is 1.14 times larger th an 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) a re 2400, 760, and 240 (based on the values for absolute global warming pote ntial for carbon dioxide reported by Intergovernmental Panel on Climate Cha nge [1996]) at integration time horizons of 20, 100, and 500 years, respect ively.