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dc.contributor.authorKeeble, Jamesen
dc.description.abstractStratospheric ozone and water vapor are key components of the Earth system, and past and future changes to both have important impacts on global and regional climate. Here we evaluate long-term changes in these species from the pre-industrial (1850) to the end of the 21st century in CMIP6 models under a range of future emissions scenarios. There is good agreement between the CMIP multi-model mean and observations for total column ozone (TCO), although there is substantial variation between the individual CMIP6 models. For the CMIP6 multi-model mean, global mean TCO has increased from ~300 DU in 1850 to ~305 DU in 1960, before rapidly declining in the 1970s and 1980s following the use and emission of halogenated ozone depleting substances (ODSs). TCO is projected to return to 1960’s values by the middle of the 21st century under the SSP2-4.5, SSP3-7.0, SSP4-3.4, SSP4-6.0 and SSP5-8.5 scenarios, and under the SSP3-7.0 and SSP5-8.5 scenarios TCO values are projected to be ~10 DU higher than the 1960’s values by 2100. However, under the SSP1-1.9 and SSP1-1.6 scenarios, TCO is not projected to return to the 1960’s values despite reductions in halogenated ODSs due to decreases in tropospheric ozone mixing ratios. This global pattern is similar to regional patterns, except in the tropics where TCO under most scenarios is not projected to return to 1960’s values, either through reductions in tropospheric ozone under SSP1-1.9 and SSP1-2.6, or through reductions in lower stratospheric ozone resulting from an acceleration of the Brewer-Dobson Circulation under other SSPs. In contrast to TCO, there is poorer agreement between the CMIP6 multi-model mean and observed lower stratospheric water vapour mixing ratios, with the CMIP6 multi-model mean underestimating observed water vapour mixing ratios by ~0.5 ppmv at 70hPa. CMIP6 multi-model mean stratospheric water vapor mixing ratios in the tropical lower stratosphere have increased by ~0.5 ppmv from the pre-industrial to the present day and are projected to increase further by the end of the 21st century. The largest increases (~2 ppmv) are simulated under the future scenarios with the highest assumed forcing pathway (e.g. SSP5-8.5). Tropical lower stratospheric water vapor, and to a lesser extent TCO, show large variations following explosive volcanic eruptions.
dc.description.sponsorshipJK and PTG thank NERC for financial support through NCAS (grant no. R8/H12/83/003). BH was supported by the European Union’s Horizon 2020 Framework Programme for Research and Innovation “Coordinated Research in Earth Systems and Climate: Experiments, kNowledge, Dissemination and Outreach (CRESCENDO)” project under grant agreement no. 641816. GZ and OM were supported by the NZ Government’s Strategic Science Investment Fund (SSIF) through the NIWA programme CACV. MD was supported by the Japan Society for the Promotion of Science (grant no. JP20K04070). GC was supported by the Swiss National Science Foundation within the Ambizione programme (grant no. PZ00P2_180043). The work of SB and OCS was supported by the Energy Exascale Earth System Model (E3SM) project, funded by the US Department of Energy, Office of Science, Office of Biological and Environmental Research. The work of PCS was performed at LLNL under contract no. DE-AC52-07NA27344. The E3SM data were produced using resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under contract no. DE-AC02-05CH11231.
dc.publisherCopernicus Publications
dc.rightsCreative Commons Attribution 4.0 License
dc.titleKeeble et al. Evaluating stratospheric ozone and water vapour changes in CMIP6 models from 1850-2100en
prism.publicationNameAtmospheric Chemistry and Physicsen
dc.contributor.orcidKeeble, James [0000-0003-2714-1084]
rioxxterms.typeJournal Article/Reviewen
pubs.funder-project-idNational Centre for Atmospheric Science (NERC) (via University of Leeds) (R8/H12/83/003)
pubs.funder-project-idNational Centre for Atmospheric Science (NERC) (via University of Leeds) (R8/H12/83/003)

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