The role of refrigerants in climate change

The primary chemicals used as refrigerants, chlorofluorocarbons (CFCs), and the compounds being considered as their replacements (HCHCs and HFCs) have been intensely studied because of concerns about chlorine chemistry effects on stratospheric ozone. Increasing attention is being given to the potential contributions of these compounds to global warming. CFCs, HCFCs and HFCs absorb infra-red radiation and thus are greenhouse gases that can exert an additional radiative forcing that tends to warm the climate. The purpose of this paper is to describe the current understanding of the role of refrigerants in affecting climate. Increasing atmospheric concentrations of CFCs have accounted for about 24% of the direct increase in radiative forcing from greenhouse gases over the last decade. However, an observed decrease in stratospheric ozone, thought to be connected to increasing stratospheric chlorine from CFCs (and, to a lesser extent, from other man-made compounds containing chlorine and bromine), suggests a negative radiative forcing or cooling tendency over the last decade. This cooling tendency has strong latitudinal gradients, but is, when globally averaged, about comparable in magnitude and opposite in sign to the radiative forcing from CFCs over this period. On the other hand, the radiative influence on climate from the compounds being considered as replacements, because of their shorter atmospheric lifetimes, should generally be much smaller than the CFCs. However, the effects on ozone should also be much smaller from the replacement compounds and there should be less cancellation in the overall globally averaged influence on climate. On a étudié en détail les produits chimiques primaires utilisés comme frigorigènes, les chlorofluorocarbures (CFC) et les composés considérés comme remplaçants (HCFC et HFC), à cause de l'effect toxique du chlore sur l'ozone stratosphérique. On a étudié en particulier l'effet possible de ces composés sur le réchauffement de la planète. Les CFC, HCFC et HFC absorbent les rayonnements infrarouges et sont donc considérés comme gas à effet de serre pouvant contribuer à des rayonnements radiatifs supplémentaires et réchauffer ainsi le climat. L'article décrit l'état des connaissances actuelles sur l'influence des frigorigènes sur la détérioration du climat. L'augmentation des teneurs en CFC dans l'atmosphère a contribué pour 24% aux émissions radiatives pendant les dix dernières années. Néanmoins, l'observation de la diminution