ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-9451-2010 Multi-model assessment of stratospheric ozone return dates and ozone recovery in CCMVal-2 models Eyring V. 1 Cionni I. 1 Bodeker G. E. 2 Charlton-Perez A. J. 3 Kinnison D. E. 4 Scinocca J. F. 5 Waugh D. W. 6 Akiyoshi H. 7 Bekki S. 8 Chipperfield M. P. 9 Dameris M. 1 Dhomse S. 9 Frith S. M. 10 Garny H. 1 Gettelman A. 4 Kubin A. 11 Langematz U. 11 Mancini E. 12 Marchand M. 8 Nakamura T. 7 Oman L. D. 6 13 Pawson S. 13 Pitari G. 12 Plummer D. A. 5 Rozanov E. 14 15 Shepherd T. G. 16 Shibata K. 17 Tian W. 9 Braesicke P. 18 Hardiman S. C. 19 Lamarque J. F. 4 Morgenstern O. 18 20 Pyle J. A. 18 Smale D. 20 Yamashita Y. 7 21 Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany Bodeker Scientific, Alexandra, New Zealand University of Reading, Department of Meteorology, Reading, UK National Center for Atmospheric Research, Boulder, CO, USA Environment Canada, Victoria, BC, Canada Johns Hopkins University, Department of Earth and Planetary Sciences, Baltimore, Maryland, USA National Institute for Environmental Studies, Tsukuba, Japan Service d'Aeronomie, Institut Pierre-Simone Laplace, Paris, France Institute for Climate and Atmospheric Science, University of Leeds, UK Science Systems and Applications, Inc., Lanham MD 20706, USA Freie Universität Berlin, Institut für Meteorologie, Berlin, Germany Università L'Aquila, Dipartimento di Fisica, L'Aquila, Italy NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center, Davos, Switzerland Institute for Atmospheric and Climate Science ETH, Zurich, Switzerland University of Toronto, Department of Physics, Canada Meteorological Research Institute, Tsukuba, Japan University of Cambridge, Department of Chemistry, Cambridge, UK Met Office, Exeter, UK National Institute of Water and Atmospheric Research, Lauder, New Zealand Center for Climate System Research, University of Tokyo, Japan 07 10 2010 10 19 9451 9472 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/10/9451/2010/acp-10-9451-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/9451/2010/acp-10-9451-2010.pdf

Projections of stratospheric ozone from a suite of chemistry-climate models (CCMs) have been analyzed. In addition to a reference simulation where anthropogenic halogenated ozone depleting substances (ODSs) and greenhouse gases (GHGs) vary with time, sensitivity simulations with either ODS or GHG concentrations fixed at 1960 levels were performed to disaggregate the drivers of projected ozone changes. These simulations were also used to assess the two distinct milestones of ozone returning to historical values (ozone return dates) and ozone no longer being influenced by ODSs (full ozone recovery). The date of ozone returning to historical values does not indicate complete recovery from ODSs in most cases, because GHG-induced changes accelerate or decelerate ozone changes in many regions. In the upper stratosphere where CO<sub>2</sub>-induced stratospheric cooling increases ozone, full ozone recovery is projected to not likely have occurred by 2100 even though ozone returns to its 1980 or even 1960 levels well before (~2025 and 2040, respectively). In contrast, in the tropical lower stratosphere ozone decreases continuously from 1960 to 2100 due to projected increases in tropical upwelling, while by around 2040 it is already very likely that full recovery from the effects of ODSs has occurred, although ODS concentrations are still elevated by this date. In the midlatitude lower stratosphere the evolution differs from that in the tropics, and rather than a steady decrease in ozone, first a decrease in ozone is simulated from 1960 to 2000, which is then followed by a steady increase through the 21st century. Ozone in the midlatitude lower stratosphere returns to 1980 levels by ~2045 in the Northern Hemisphere (NH) and by ~2055 in the Southern Hemisphere (SH), and full ozone recovery is likely reached by 2100 in both hemispheres. Overall, in all regions except the tropical lower stratosphere, full ozone recovery from ODSs occurs significantly later than the return of total column ozone to its 1980 level. The latest return of total column ozone is projected to occur over Antarctica (~2045–2060) whereas it is not likely that full ozone recovery is reached by the end of the 21st century in this region. Arctic total column ozone is projected to return to 1980 levels well before polar stratospheric halogen loading does so (~2025–2030 for total column ozone, cf. 2050–2070 for Cl<sub>y</sub>+60&times;Br<sub>y</sub>) and it is likely that full recovery of total column ozone from the effects of ODSs has occurred by ~2035. In contrast to the Antarctic, by 2100 Arctic total column ozone is projected to be above 1960 levels, but not in the fixed GHG simulation, indicating that climate change plays a significant role.

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