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Attribution of stratospheric and tropospheric ozone changes between 1850 and 2014 in CMIP6 models
  • +18
  • Guang Zeng,
  • Nathan Luke Abraham,
  • Alexander Thomas Archibald,
  • Susanne E. Bauer,
  • Makoto Deushi,
  • Louisa K. Emmons,
  • Paul Thomas Griffiths,
  • Birgit Hassler,
  • Larry Wayne Horowitz,
  • James Keeble,
  • Michael James Mills,
  • Olaf Morgenstern,
  • Lee Thomas Murray,
  • Vaishali Naik,
  • Fiona M. O'Connor,
  • Naga Oshima,
  • Lori T. Sentman,
  • Simone Tilmes,
  • Kostas Tsigaridis,
  • Jonny Williams,
  • Paul J Young
Guang Zeng
National Institute of Water and Atmospheric Research

Corresponding Author:[email protected]

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Nathan Luke Abraham
NCAS, University of Cambridge
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Alexander Thomas Archibald
University of Cambridge
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Susanne E. Bauer
NASA Goddard Institute for Space Studies, New York, NY, USA
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Makoto Deushi
Meteorological Research Institute
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Louisa K. Emmons
National Center for Atmospheric Research (UCAR)
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Paul Thomas Griffiths
University of Cambridge
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Birgit Hassler
Deutsches Zentrum fur Luft- und Raumfahrt (DLR), Institut fur Physik der Atmosphare
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Larry Wayne Horowitz
GFDL/NOAA
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James Keeble
University of Cambridge
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Michael James Mills
National Center for Atmospheric Research (UCAR)
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Olaf Morgenstern
NIWA
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Lee Thomas Murray
University of Rochester
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Vaishali Naik
NOAA GFDL
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Fiona M. O'Connor
Met Office Hadley Centre
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Naga Oshima
Meteorological Research Institute
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Lori T. Sentman
National Oceanic and Atmospheric Administration/Geophysical Fluid Dynamics Laboratory
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Simone Tilmes
National Center for Atmospheric Research (UCAR)
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Kostas Tsigaridis
Center for Climate Systems Research, Columbia University, and NASA Goddard Institute for Space Studies
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Jonny Williams
NIWA
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Paul J Young
Lancaster University
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Abstract

We quantify the impacts of halogenated ozone-depleting substances (ODSs), methane, N2O, CO2, and short-lived ozone precursors on total and partial ozone column changes between 1850 and 2014 using CMIP6 Aerosol and Chemistry Model Intercomparison Project (AerChemMIP) simulations. We find that whilst substantial ODS-induced ozone loss dominates the stratospheric ozone changes since the 1970s, the increases in short-lived ozone precursors and methane lead to increases in tropospheric ozone since the 1950s that make increasingly important contributions to total column ozone (TCO) changes. Our results show that methane impacts stratospheric ozone changes through its reaction with atomic chlorine leading to ozone increases, but this impact will decrease with declining ODSs. The N2O increases mainly impact ozone through NOx-induced ozone destruction in the stratosphere, having an overall small negative impact on TCO. CO2 increases lead to increased global stratospheric ozone due to stratospheric cooling. However, importantly CO2 increases cause TCO to decrease in the tropics. Large interannual variability obscures the responses of stratospheric ozone to N2O and CO2 changes. Substantial inter-model differences originate in the models’ representations of ODS-induced ozone depletion. We find that, although the tropospheric ozone trend is driven by the increase in its precursors, the stratospheric changes significantly impact the upper tropospheric ozone trend through modified stratospheric circulation and stratospheric ozone depletion. The speed-up of stratospheric overturning (i.e. decreasing age of air) is driven mainly by ODS and CO2; increases. Changes in methane and ozone precursors also modulate the cross-tropopause ozone flux.