Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Spectroscopy and warming potentials of atmospheric greenhouse gases

Measurements have been made of the 'greenhouse' effect on the atmosphere of various halocarbons used, or intended for use, by industry as replacements for the chlorofluorocarbons being phased out under the Montreal Protocol. For most of the species, the measurements have been made in more detail and over a greater range of laboratory conditions than hitherto reported. Five experimental groups made the measurements, which were preceded by an intercomparison campaign. The results from this campaign have validated the experimental measurements. Using a radiative transfer model that have been extensively compared with a line-by-line model, there is improved confidence in the assessment of the atmospheric effects. The assessment should feed directly into future revisions of the tables of global warming potentials that support the Kyoto Protocol of the United Nations Framework Convention on Climate Change.

The work has characterized the impact of inhomogeneities in the horizontal and vertical distribution of the halocarbons using the output from a 2-dimensional transport model. A simple method, dependent on the lifetime of the species, of adjusting the radiative forcing calculated assuming the molecule to be well mixed reflects these effects. There are significant changes to current values of radiative forcing. For example, this work shows that fluoroform is 20% lower, and chloroform is more than 5 times higher than the existing values, probably because the spectroscopic measurements were made over a more appropriate range of wavelengths. One problem with some of the earlier values is that they are based on 'grey' literature and hence the methods by which they were derived are not clearly known. By contrast, both the measurements and radiative calculations resulting from this research will be fully reported in the open literature.


John BALLARD, (Division Head)
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