ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-13-2063-2013 Pre-industrial to end 21st century projections of tropospheric ozone from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) Young P. J. 1 2 26 Archibald A. T. 3 4 Bowman K. W. 5 Lamarque J.-F. 6 Naik V. 7 Stevenson D. S. 8 Tilmes S. 6 Voulgarakis A. 9 Wild O. 10 Bergmann D. 11 Cameron-Smith P. 11 Cionni I. 12 Collins W. J. 13 27 Dalsøren S. B. 14 Doherty R. M. 8 Eyring V. 15 Faluvegi G. 16 Horowitz L. W. 17 Josse B. 18 Lee Y. H. 16 MacKenzie I. A. 8 Nagashima T. 19 Plummer D. A. 20 Righi M. 15 Rumbold S. T. 13 Skeie R. B. 14 Shindell D. T. 16 Strode S. A. 21 22 Sudo K. 23 Szopa S. 24 Zeng G. 25 Cooperative Institute for Research in the Environmental Sciences, University of Colorado-Boulder, Boulder, Colorado, USA Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, Colorado, USA Centre for Atmospheric Science, University of Cambridge, Cambridge, UK National Centre for Atmospheric Science, University of Cambridge, Cambridge, UK NASA Jet Propulsion Laboratory, Pasadena, California, USA National Center for Atmospheric Research, Boulder, Colorado, USA UCAR/NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA School of GeoSciences, University of Edinburgh, Edinburgh, UK Department of Physics, Imperial College, London, UK Lancaster Environment Centre, Lancaster University, Lancaster, UK Lawrence Livermore National Laboratory, Livermore, California, USA Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile (ENEA), Bologna, Italy Met Office Hadley Centre, Exeter, UK CICERO, Center for International Climate and Environmental Research-Oslo, Oslo, Norway Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany NASA Goddard Institute for Space Studies, and Columbia Earth Institute, Columbia University, New York City, New York, USA NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA GAME/CNRM, Météo-France, CNRS – Centre National de Recherches Météorologiques, Toulouse, France Frontier Research Center for Global Change, Japan Marine Science and Technology Center, Yokohama, Japan Canadian Centre for Climate Modeling and Analysis, Environment Canada, Victoria, British Columbia, Canada NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Universities Space Research Association, Columbia, Maryland, USA Department of Earth and Environmental Science, Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan Laboratoire des Sciences du Climat et de l'Environnement, LSCE-CEA-CNRS-UVSQ, Gif-sur-Yvette, France National Institute of Water and Atmospheric Research, Lauder, New Zealand now at: Lancaster Environment Centre, Lancaster University, Lancaster, UK now at: Department of Meteorology, University of Reading, Reading, UK 21 02 2013 13 4 2063 2090 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/13/2063/2013/acp-13-2063-2013.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/13/2063/2013/acp-13-2063-2013.pdf

Present day tropospheric ozone and its changes between 1850 and 2100 are considered, analysing 15 global models that participated in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). The ensemble mean compares well against present day observations. The seasonal cycle correlates well, except for some locations in the tropical upper troposphere. Most (75 %) of the models are encompassed with a range of global mean tropospheric ozone column estimates from satellite data, but there is a suggestion of a high bias in the Northern Hemisphere and a low bias in the Southern Hemisphere, which could indicate deficiencies with the ozone precursor emissions. Compared to the present day ensemble mean tropospheric ozone burden of 337 ± 23 Tg, the ensemble mean burden for 1850 time slice is ~30% lower. Future changes were modelled using emissions and climate projections from four Representative Concentration Pathways (RCPs). Compared to 2000, the relative changes in the ensemble mean tropospheric ozone burden in 2030 (2100) for the different RCPs are: −4% (−16%) for RCP2.6, 2% (−7%) for RCP4.5, 1% (−9%) for RCP6.0, and 7% (18%) for RCP8.5. Model agreement on the magnitude of the change is greatest for larger changes. Reductions in most precursor emissions are common across the RCPs and drive ozone decreases in all but RCP8.5, where doubled methane and a 40–150% greater stratospheric influx (estimated from a subset of models) increase ozone. While models with a high ozone burden for the present day also have high ozone burdens for the other time slices, no model consistently predicts large or small ozone changes; i.e. the magnitudes of the burdens and burden changes do not appear to be related simply, and the models are sensitive to emissions and climate changes in different ways. Spatial patterns of ozone changes are well correlated across most models, but are notably different for models without time evolving stratospheric ozone concentrations. A unified approach to ozone budget specifications and a rigorous investigation of the factors that drive tropospheric ozone is recommended to help future studies attribute ozone changes and inter-model differences more clearly.

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