Ozone-Depleting Compounds On Decline In Atmosphere

Chlorofluorocarbons and hydrochlorofluorocarbons (HCFCs) are valued as refrigerants and propellants. When they are released to the atmosphere, however, they destroy Earth’s protective ozone layer. Although an international treaty controls the use of such compounds, a study last year indicated that concentrations of some of them continued to increase through 2012. Follow-up measurements now indicate that concentrations of two HCFCs, CH₂ClF and CF₃CH₂Cl, peaked around 2012 and have since steeply declined, with emissions dropping by as much as 50% in three years (Geophys. Res. Lett. 2015, DOI: 10.1002/2015gl064709 and 10.1002/2015gl065846). The compounds were studied by international teams led by Fabian Schoenenberger and Martin K. Vollmer of the Swiss Federal Laboratories for Materials Science & Technology. CH₂ClF has been used to a limited extent in refrigerant blends, and CF₃CH₂Cl has no known industrial use. The researchers propose that the compounds are most likely produced and emitted as intermediates or by-products of manufacturing HCFCs and that the decrease is probably due to a change in the processes that make those HCFCs. Emissions from other sources would be unlikely to show the observed steep decline.