Abstract
It is well established that anthropogenic chlorine-containing chemicals contribute to ozone layer depletion. The successful implementation of the Montreal Protocol has led to reductions in the atmospheric concentration of many ozone-depleting gases, such as chlorofluorocarbons. As a consequence, stratospheric chlorine levels are declining and ozone is projected to return to levels observed pre-1980 later this century. However, recent observations show the atmospheric concentration of dichloromethane—an ozone-depleting gas not controlled by the Montreal Protocol—is increasing rapidly. Using atmospheric model simulations, we show that although currently modest, the impact of dichloromethane on ozone has increased markedly in recent years and if these increases continue into the future, the return of Antarctic ozone to pre-1980 levels could be substantially delayed. Sustained growth in dichloromethane would therefore offset some of the gains achieved by the Montreal Protocol, further delaying recovery of Earth’s ozone layer.
Highlights
It is well established that anthropogenic chlorine-containing chemicals contribute to ozone layer depletion
The abundance of CH2Cl2 at mid-latitudes in the Northern Hemisphere (NH) is around a factor of 3 greater than in the Southern Hemisphere (SH), reflecting NH industrial sources
A specific use of CH2Cl2, which seems likely to have increased in recent years, is in the manufacture of hydrofluorocarbons—the non-ozone-depleting chemicals used as replacements for CFCs and hydrochlorofluorocarbons (HCFCs)
Summary
It is well established that anthropogenic chlorine-containing chemicals contribute to ozone layer depletion. In the 1970s, it was recognized that chlorine and bromine released from long-lived anthropogenic compounds, such as chlorofluorocarbons (CFCs) and halons, could destroy ozone in the stratosphere[1,2] Industrial emissions of these halocarbons have led to widespread depletion of Earth’s ozone layer in recent decades, including the Antarctic ‘Ozone Hole’ phenomenon[3,4,5]. While the precise nature of the source remains poorly characterized, industrial CH2Cl2 emissions from Asia—in particular from the Indian subcontinent—appear to be growing in importance[23] The impact of these observed changes and continued CH2Cl2 growth in coming decades on the timescale of stratospheric ozone recovery have not yet been considered. We find that continued growth in the atmospheric loading of CH2Cl2 could offset some of the future benefits of the Montreal Protocol and lead to a substantial delay (more than a decade) in the recovery of stratospheric ozone over Antarctica
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call