Unregulated ozone-depleting substance dichloromethane could delay ozone recovery

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Ozone layer

An ozone-depleting substance that isn’t being regulated currently has the potential of delaying ozone recovery over Antarctic by up to 30 years a new study has shown.

Researchers have pointed out in a study published in Nature Communications that the currently unregulated dichloromethane could be contributing to ozone depletion and should be looked at to improve future ozone predictions. According to current predictions, the Antarctic ‘ozone hole’ is expected to fully recover sometime between 2046 and 2057. However, dichloromethane concentrations are increasing in the atmosphere because it is an unregulated substance and its concentrations have reached levels that could be contributing to ozone loss.

Study lead author Dr Ryan Hossaini, from the Lancaster Environment Centre at Lancaster University, notes that while the ozone depletion from dichloromethane is currently quite modest, it is uncertain how the amount of this gas in the atmosphere will change in the future. Their study has shown that continued sustained growth in its concentration could substantially delay recovery of the ozone layer, offsetting some of the future benefits of the Montreal Protocol.

For the study scientists use simulations with a global chemical transport model to examine the sensitivity of future stratospheric chlorine and ozone levels to sustained dichloromethane growth. Measurements of dichloromethane in the atmosphere over the past two decades, provided by scientists from the National Oceanic and Atmospheric Administration (NOAA) in the United States, were also analysed.

Their projections show that continued dichloromethane increases at the average trend observed from 2004-2014 would delay ozone recovery over Antarctica by 30 years. If dichloromethane concentrations stay at current levels, the delay in recovery would be only 5 years. Although the future trajectory of dichloromethane is uncertain, without any regulations on emissions, it is likely concentrations will fall somewhere in between the ranges presented here.

The ozone layer shields Earth’s surface from certain wavelengths of harmful solar ultraviolet (UV) radiation that would otherwise be detrimental to human, animal and plant health. Ozone also absorbs terrestrial infrared (IR) radiation and changes in its abundance can influence climate.

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