EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-532 Uncertainties in recent tropical stratospheric and tropospheric ozone changes restrict our understanding of future total column ozone change Davis Sean https://orcid.org/0000-0001-9276-6158 1 Ball William 2 3 44 Jia Yue https://orcid.org/0000-0003-2210-9050 4 Chiodo Gabriel https://orcid.org/0000-0002-8079-6314 5 Alsing Justin 6 Keeble James https://orcid.org/0000-0003-2714-1084 7 Akiyoshi Hideharu https://orcid.org/0000-0001-6463-9004 8 Arosio Carlo https://orcid.org/0000-0002-8759-6390 9 Bednarz Ewa https://orcid.org/0000-0002-7441-0497 10 1 Chrysanthou Andreas https://orcid.org/0000-0002-8670-5436 11 12 42 Coldewey-Egbers Melanie https://orcid.org/0000-0002-9275-498X 13 Damadeo Robert https://orcid.org/0000-0002-1466-839X 14 Dhomse Sandip https://orcid.org/0000-0003-3854-5383 11 15 Diallo Mohamadou https://orcid.org/0000-0003-0225-8120 16 Dietmuller Simone 17 Eichinger Roland https://orcid.org/0000-0001-6872-5700 17 18 Frith Stacey 19 20 Hassler Birgit https://orcid.org/0000-0003-2724-709X 17 Hegglin Michaela 21 22 23 Hubert Daan https://orcid.org/0000-0002-4365-865X 24 Jöckel Patrick https://orcid.org/0000-0002-8964-1394 17 Josse Béatrice 25 Kramarova Natalya https://orcid.org/0000-0002-6083-8548 20 Loyola Diego https://orcid.org/0000-0002-8547-9350 13 Maillard Barras Eliane https://orcid.org/0000-0002-6513-8428 26 Marchand Marion 27 Morgenstern Olaf https://orcid.org/0000-0002-9967-9740 28 29 43 Plummer David https://orcid.org/0000-0001-8087-3976 30 Portmann Robert https://orcid.org/0000-0002-0279-6087 1 Rosenlof Karen https://orcid.org/0000-0002-0903-8270 31 45 Rozanov Alexei https://orcid.org/0000-0003-4525-3223 8 Sofieva Viktoria https://orcid.org/0000-0002-9192-2208 32 Staehelin Johannes https://orcid.org/0000-0001-7861-1889 33 Sukhodolov Timofei https://orcid.org/0000-0001-7100-738X 34 Tourpali Kleareti 35 Van der A Ronald https://orcid.org/0000-0002-0077-5338 3 Wang H. J. Ray https://orcid.org/0000-0002-1550-3239 36 Wargan Krzysztof https://orcid.org/0000-0002-3795-2983 20 37 Watanabe Shingo 38 39 Weber Mark https://orcid.org/0000-0001-8217-5450 9 Wild Jeannette 40 45 Yamashita Yousuke https://orcid.org/0000-0002-6813-4668 8 Ziemke Jerry 20 41 NOAA Chemical Sciences Laboratory, Boulder, CO, USA Department of Geoscience and Remote Sensing, TU Delft, Delft, The Netherlands Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands Univ. of Texas at Dallas, Dallas, TX, USA Instituto de Geociencias, Consejo Superior de Investigaciones Cientificas (IGEO-CSIC), Madrid, Spain Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, Stockholm, Sweden Lancaster Environment Centre, Lancaster University, Lancaster, UK Earth System Division, National Institute for Environmental Studies, Ibaraki, Japan Institute of Environmental Physics, University of Bremen, Bremen, Germany Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado at Boulder, Boulder, CO, USA School of Earth and Environment, University of Leeds, Leeds, UK Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Greece Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut fur Methodik der Fernerkundung, Oberpfaffenhofen, Germany NASA Langley Research Center, Hampton, VA, USA National Centre for Earth Observation (NCEO), University of Leeds, Leeds, UK Institute of Climate and Energy Systems – Stratosphere (ICE-4), Forschungszentrum Jülich, Germany Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany Department of Atmospheric Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic Adnet Systems, Inc., Lanham, MD, USA NASA Goddard Space Flight Center, Greenbelt, MD, USA Institute of Climate and Energy Systems - Stratosphere, Forschungszentrum Jülich, Jülich, Germany Institute for Atmospheric and Environmental Research, University of Wuppertal, Wuppertal, Germany Department of Meteorology, University of Reading, Reading, United Kingdom Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium CNRM, Université de Toulouse, Météo‐France, CNRS, Toulouse, France Federal Office of Meteorology and Climatology, MeteoSwiss, Payerne, Switzerland LATMOS, Institut Pierre‐Simon Laplace, Sorbonne Université/CNRS/UVSQ, Paris, France National Institute of Water and Atmospheric Research, Te Whanganui-a-Tara / Wellington, Aotearoa New Zealand School of Physical and Chemical Sciences, Canterbury University, Ōtautahi / Christchurch, Aotearoa New Zealand Climate Research Division, Environment and Climate Change Canada, Montreal, QC, Canada NOAA Chemical Sciences Laboratory, Boulder, CO, USA (now retired) Finnish Meteorological Institute, Helsinki, Finland Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland Physikalisch Meteorologisches Observatorium Davos/World Radiation Center, Davos, Switzerland Aristotle University of Thessaloniki, Thessaloniki, Greece School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA Science Systems and Applications Inc., MD, USA Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokohama, Japan Advanced Institute for Marine Ecosystem Change (WPI-AIMEC), Tohoku University, Sendai, Japan ESSIC/UMD & NOAA/NESDIS/STAR, College Park, MD, USA (now retired) Morgan State University, Baltimore, MD, USA now at: Instituto de Geociencias, Consejo Superior de Investigaciones Cientificas (IGEO-CSIC), Madrid, Spain now at: Deutscher Wetterdienst, Offenbach, Germany deceased retired 26 02 2026 2026 1 44 Copyright: © 2026 Sean Davis et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-532/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-532/egusphere-2026-532.pdf

A variety of chemical and dynamical processes in the troposphere and stratosphere affect tropical total column ozone (TCO), the net effect of which may cause changes in surface UV radiation and impact human and ecosystem health. We use dynamical linear modeling to estimate tropical trends in TCO and partial column ozone (PCO) in the troposphere and three stratospheric layers to assess agreement between satellite observational composites and chemistry&ndash;climate model (CCM) simulations from two multi-model experiments (CCMI-1 and CCMI-2022). While both model experiments show tropical TCO increases over 2000&ndash;2021, CCMI&ndash;2022 trends (+2.5 DU) agree slightly better with observations than CCMI-1 (+1.6 DU). However, this overall agreement obscures multiple systematic differences in PCO trends between the models and observations across atmospheric layers. For example, since 2000 tropical tropospheric PCO increased significantly in CCMI-2022 (+1.5 DU) but not in CCMI&ndash;1 (+0.3 DU), largely explaining the difference in TCO trends. Also, despite nearly identical stratospheric PCO trends, CCMI-2022 trends are slightly more negative in the lower stratospheric (by ~0.5 DU), compensated by more positive middle/upper stratosphere trends compared to CCMI-1. Crucially, substantial differences exist across observational PCO trends, particularly in the troposphere and middle/upper stratosphere, and these disagreements limit the ability to evaluate CCM fidelity. Furthermore, while the inter-model correlation between late and early 21<sup>st</sup> century trends is suggestive of a potential emergent constraint on future ozone trends, the spread in observational trends precludes its observational implementation.