Modelling the potential impacts of the recent, unexpected increase in CFC-11 emissions on total column ozone recovery
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Published:2020-06-19
Issue:12
Volume:20
Page:7153-7166
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Keeble JamesORCID, Abraham N. LukeORCID, Archibald Alexander T.ORCID, Chipperfield Martyn P.ORCID, Dhomse SandipORCID, Griffiths Paul T.ORCID, Pyle John A.ORCID
Abstract
Abstract. The temporal evolution of the abundance of long-lived,
anthropogenic chlorofluorocarbons in the atmosphere is a major factor in
determining the timing of total column ozone (TCO) recovery. Recent
observations have shown that the atmospheric mixing ratio of CFC-11 is not
declining as rapidly as expected under full compliance with the Montreal
Protocol and indicate a new source of CFC-11 emissions. In this study, the
impact of a number of potential future CFC-11 emissions scenarios on the
timing of the TCO return to the 1960–1980 mean (an important milestone on the
road to recovery) is investigated using the Met Office's Unified Model
(Hewitt et al., 2011) coupled with the United Kingdom Chemistry and Aerosol
scheme (UM-UKCA). Key uncertainties
related to this new CFC-11 source and their impact on the timing of the TCO
return date are explored, including the duration of new CFC-11 production
and emissions; the impact of any newly created CFC-11 bank; and the effects
of co-production of CFC-12. Scenario-independent relationships are
identified between cumulative CFC emissions and the timing of the TCO return
date, which can be used to establish the impact of future CFC emissions
pathways on ozone recovery in the real world. It is found that, for every
200 Gg Cl (∼258 Gg CFC-11) emitted, the timing of the global TCO return to 1960–1980 averaged values is delayed by ∼0.56 years. However, a marked hemispheric asymmetry in the latitudinal impacts of
cumulative Cl emissions on the timing of the TCO return date is identified,
with longer delays in the Southern Hemisphere than the Northern Hemisphere
for the same emission. Together, these results indicate that, if rapid
action is taken to curb recently identified CFC-11 production, then no
significant delay in the timing of the TCO return to the 1960–1980 mean is
expected, highlighting the importance of ongoing, long-term measurement
efforts to inform the accountability phase of the Montreal Protocol.
However, if the emissions are allowed to continue into the future and are
associated with the creation of large banks, then significant delays in the
timing of the TCO return date may occur.
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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