A growing threat to the ozone layer from short-lived anthropogenic chlorocarbons
Large and effective reductions in emissions of long-lived ozone-depleting substance (ODS) are being achieved through the Montreal Protocol, the effectiveness of which can be seen in the declining atmospheric abundances of many ODSs. An important remaining uncertainty concerns the role of very sh...
Main Authors: | , , , , , , , , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2017-10-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/17/11929/2017/acp-17-11929-2017.pdf |
Summary: | Large and effective reductions in emissions of long-lived ozone-depleting
substance (ODS) are being achieved through the Montreal Protocol, the
effectiveness of which can be seen in the declining atmospheric abundances
of many ODSs. An important remaining uncertainty concerns the role of very
short-lived substances (VSLSs) which, owing to their relatively short
atmospheric lifetimes (less than 6 months), are not regulated under the
Montreal Protocol. Recent studies have found an unexplained increase in the
global tropospheric abundance of one VSLS, dichloromethane
(CH<sub>2</sub>Cl<sub>2</sub>), which has increased by around 60 % over the past
decade. Here we report dramatic enhancements of several chlorine-containing
VSLSs (Cl-VSLSs), including CH<sub>2</sub>Cl<sub>2</sub> and CH<sub>2</sub>ClCH<sub>2</sub>Cl
(1,2-dichloroethane), observed in surface and upper-tropospheric air in East
and South East Asia. Surface observations were, on occasion, an order of
magnitude higher than previously reported in the marine boundary layer,
whilst upper-tropospheric data were up to 3 times higher than expected. In addition, we provide further evidence of an atmospheric transport mechanism
whereby substantial amounts of industrial pollution from East Asia,
including these chlorinated VSLSs, can rapidly, and regularly, be transported
to tropical regions of the western Pacific and subsequently uplifted to the
tropical upper troposphere. This latter region is a major provider of air
entering the stratosphere, and so this mechanism, in conjunction with
increasing emissions of Cl-VSLSs from East Asia, could potentially slow the
expected recovery of stratospheric ozone. |
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ISSN: | 1680-7316 1680-7324 |