Simplified approach to calculating global warming potentials developed.

NIST scientists, in collaboration with researchers from the Institute of Energy Problems of Chemical Physics, Russian Academy of Sciences, have developed a simplified method of calculating global warming potentials (GWPs) of halogenated compounds. The method appears in a paper published in the Journal of Photochemistry and Photobiology. A. Chemistry 157, 211-222 (2003), along with measured infrared absorption cross sections and integrated band intensities for 21 haloalkanes of industrial importance. This new approach for GWP calculation is valid for compounds whose principal IR absorption bands do not overlap those of carbon dioxide and are sufficiently long-lived that their tropospheric vertical distributions are approximately constant. This is true for numerous compounds of industrial interest, which are expected to contribute to the global warming. The method utilizes the measured infrared absorption cross-sections of the molecule along with the measured outgoing infrared emission of the earth to derive the radiative forcing. The radiative forcing together with an atmospheric lifetime determined from laboratory photochemical kinetic measurements is then used to derive the GWP of the compound. For the 12 compounds for which literature values exist, the values calculated by this simplified approach are found to be in very good agreement with the results of comprehensive atmospheric modeling.

The infrared absorption spectra measured in this work along with spectra for three fluoroethers are posted on the web at http://nist.gov/kinetics/spectra/ spectraindex.htm. A number of UV absorption spectra measured at NIST can be found at the same web site.

CONTACT: Vladimir Orkin, [phone]; [e-mail].