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Global warming potentials and radiative efficiencies of halocarbons and related compounds: a comprehensive review

This review article is concerned with the radiative efficiencies (REs) and global warming potentials (GWPs) of a very wide range of halocarbons. The paper describes original research and a number of new insights into global warming. First, the paper is much more than a review of what has already been calculated and reported; where infrared data are available, REs have been recalculated using a consistent method, and where molecular lifetimes are available, GWPs have also been recalculated. This approach allows a direct comparison between the impact on climate change of different halocarbon compounds, without the uncertainties that have arisen in the past from a range of different methods being used. Previous methods have, for example, used different cloudiness, chemical and temperature distribution and temperature adjustment. Secondly, the method for converting infrared spectra into REs has been assessed and revised, with an improved representation of clouds, and spatial distributions of temperature and water vapour; furthermore, the resolution of the method has been improved ten-fold (from 10 cm-1 to 1 cm-1). Finally, the usual methods for RE calculation do not apply to short-lived gases because the gases are not evenly distributed throughout the atmosphere. In work described in the present paper, new computer simulations were carried out using a chemical transport model combined with a radiative transfer model to simulate the impact of short-lived gases on climate. The simulations take into account temporal and spatial variations in emissions and allow REs to be determined for short-lived gases. The publication of this article was highlighted and discussed in Chemical and Engineering News [91, 34, 27 – 28 (2013)]. Most importantly, the work reported in this paper features in Chapter 8 of Working Group I’s contribution to the IPCC’s Fifth Assessment Report on Climate Change, of which Marston is a contributing author.