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| Titel |
How sensitive is the recovery of stratospheric ozone to changes in concentrations of very short-lived bromocarbons? |
| VerfasserIn |
X. Yang, N. L. Abraham, A. T. Archibald, P. Braesicke, J. Keeble, P. J. Telford, N. J. Warwick, J. A. Pyle |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 19 ; Nr. 14, no. 19 (2014-10-01), S.10431-10438 |
| Datensatznummer |
250119076
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| Publikation (Nr.) |
 copernicus.org/acp-14-10431-2014.pdf |
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| Zusammenfassung |
| Naturally produced very short-lived substances (VSLS) account for almost a
quarter of the current stratospheric inorganic bromine, Bry.
Following VSLS oxidation, bromine radicals (Br and BrO) can catalytically
destroy ozone. The extent to which possible increases in surface emissions or
transport of these VSLS bromocarbons to the stratosphere could counteract the
effect of halogen reductions under the Montreal Protocol is an important
policy question. Here, by using a chemistry–climate model, UM-UKCA, we
investigate the impact of a hypothetical doubling (an increase of 5 ppt
Bry) of VSLS bromocarbons on ozone and how the resulting ozone
changes depend on the background concentrations of chlorine and bromine. Our
model experiments indicate that for the 5 ppt increase in Bry
from VSLS, the ozone decrease in the lowermost stratosphere of the Southern
Hemisphere (SH) may reach up to 10% in the annual mean; the ozone
decrease in the Northern Hemisphere (NH) is smaller (4–6%). The largest
impact on the ozone column is found in the Antarctic spring. There is a
significantly larger ozone decrease following the doubling of the VSLS burden
under a high stratospheric chlorine background than under a low chlorine
background, indicating the importance of the inter-halogen reactions. For
example, the decline in the high-latitude, lower-stratospheric ozone
concentration as a function of Bry is higher by about
30–40% when stratospheric Cly is ~ 3 ppb (present
day), compared with Cly of ~ 0.8 ppb (a pre-industrial or
projected future situation). Bromine will play an important role in the future
ozone layer. However, even if bromine levels from natural VSLS were to
increase significantly later this century, changes in the concentration of
ozone will likely be dominated by the decrease in anthropogenic chlorine. Our
calculation suggests that for a 5 ppt increase in Bry from VSLS,
the Antarctic ozone hole recovery date could be delayed by approximately 6–8
years, depending on Cly levels. |
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