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Preprints
https://doi.org/10.5194/acp-2019-747
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2019-747
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 02 Oct 2019

Submitted as: research article | 02 Oct 2019

Review status
A revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Modelling the potential impacts of the recent, unexpected increase in CFC-11 emissions on total column ozone recovery

James Keeble1,2, N. Luke Abraham1,2, Alexander T. Archibald1,2, Martyn P. Chipperfield3,4, Sandip Dhomse3,4, Paul T. Griffiths1,2, and John A. Pyle1,2 James Keeble et al.
  • 1Department of Chemistry, University of Cambridge, Cambridge, UK
  • 2National Centre for Atmospheric Science (NCAS), University of Cambridge, Cambridge, UK
  • 3School of Earth and Environment, University of Leeds, Leeds, UK
  • 4National Centrefor Earth Observation (NCEO), University of Leeds, Leeds, UK

Abstract. The temporal evolution of long-lived, anthropogenic chlorofluorocarbons is a key control on the timing of total column ozone (TCO) recovery. Recent observations have shown that the atmospheric mixing ratio of CFC-11 is not declining as expected under complete compliance with the Montreal Protocol, and indicate a new source of CFC-11. In this study, the impact of a number of potential future CFC-11 emissions scenarios on TCO recovery is investigated using the UM-UKCA model. Key uncertainties related to this new CFC-11 source and their impact on the timing of TCO recovery are explored, including: the duration of new CFC-11 emissions/production; the impact of any newly created bank; and the effects of co-production of CFC-12. Scenario-independent relationships are identified between cumulative CFC emissions and the timing of ozone recovery, 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 emitted, the timing of global TCO recovery is delayed by ~ 0.56 years. However, a marked hemispheric asymmetry in the latitudinal impacts of cumulative Cl emissions on the timing of TCO recovery 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 TCO recovery 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 TCO recovery may occur.

James Keeble et al.

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James Keeble et al.

James Keeble et al.

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Short summary
The Montreal Protocol was agreed in 1987 to limit and then stop the production of man-made CFCs, which destroy stratospheric ozone. As a result, the atmospheric abundances of CFCs are now declining in the atmosphere. However, the atmospheric abundance of CFC-11 is not declining as expected under complete compliance with the Montreal Protocol. Using the UM-UKCA chemistry climate model, we explore the impact of future unregulated production of CFC-11 on the timing of ozone recovery.
The Montreal Protocol was agreed in 1987 to limit and then stop the production of man-made CFCs,...
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