Historical and future changes in air pollutants from CMIP6 models

Turnock, Steven T.; Allen, Robert J.; Andrews, Martin; Bauer, Susanne E.; Deushi, Makoto; Emmons, Louisa; Good, Peter; Horowitz, Larry; John, Jasmin G.; Michou, Martine; Nabat, Pierre; Naik, Vaishali; Neubauer, David; O'Connor, Fiona M.; Olivié, Dirk; Oshima, Naga; Schulz, Michael; Sellar, Alistair; Shim, Sungbo; Takemura, Toshihiko; Tilmes, Simone; Tsigaridis, Kostas; Wu, Tongwen; Zhang, Jie

doi:https://doi.org/10.5194/acp-20-14547-2020

Articles | Volume 20, issue 23

https://doi.org/10.5194/acp-20-14547-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

The Aerosol Chemistry Model Intercomparison Project...

https://doi.org/10.5194/acp-20-14547-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 23

Research article

|

30 Nov 2020

Research article |

| 30 Nov 2020

Historical and future changes in air pollutants from CMIP6 models

Steven T. Turnock, Robert J. Allen, Martin Andrews, Susanne E. Bauer, Makoto Deushi, Louisa Emmons, Peter Good, Larry Horowitz, Jasmin G. John, Martine Michou, Pierre Nabat, Vaishali Naik, David Neubauer, Fiona M. O'Connor, Dirk Olivié, Naga Oshima, Michael Schulz, Alistair Sellar, Sungbo Shim, Toshihiko Takemura, Simone Tilmes, Kostas Tsigaridis, Tongwen Wu, and Jie Zhang

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Final revised paper (published on 30 Nov 2020)
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Preprint (discussion started on 21 Jan 2020)
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Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review of Turnock et al. "Historical and future changes in air pollutants from CMIP6 models"', Anonymous Referee #1, 15 Feb 2020
RC2: 'Review', Anonymous Referee #2, 15 Apr 2020
AC1: 'Author Response to comments from reviewer 1 and 2', Steven Turnock, 17 Jul 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Steven Turnock on behalf of the Authors (20 Jul 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 Aug 2020) by Holger Tost

RR by Anonymous Referee #2 (22 Sep 2020)

Suggestions for revision or reasons for rejection

The authors have thoroughly revised the paper and I find it suitable for publication. Again, I emphasize the enormous amount of work undertaken by the authors to document the current status of these models with respect to available observations and each other, and to address the concerns raised in the previous round of review. The new detailed table and figures, including those revised to increase readability from the first submission, will be extremely useful to future studies.

Below are a few minor comments the authors may wish to consider.

Line 43. Is this because emissions decrease in these regions even in SSP3-7?

Line 45. Prediction  projection (they are not initialized with the observed climate state).

Line 105. expenses  expense

Line 304. A recent paper suggests dynamically represented dry deposition decreases simulated ozone over North America, East Asia, and elsewhere (Clifton et al. 2020: https://doi.org/ 10.1029/2020JD032398.) Of relevance to the oceanic regions, do any of these models include tropospheric halogen chemistry?

Lines 325 and 364. Is there any obvious connection between models with higher organic aerosol and more detailed representations of SOA and/or precursor gas emissions?

Lines 529-532. Is the point here that the difference in ozone increases is not simply following differences in NOx emissions in the 2 trajectories? Can an example be given as to what might explain this finding? Could there be a role for different biogenic emission responses?

Line 586. Are the models prescribing land use change separately? I thought this was a specified forcing? Are some models allowing natural emissions to adjust when that land use change is imposed while others are only updating physical climate variables?

Lines 614-616. A bit awkward; the factor of 2 across models doesn’t have consequences for future air quality, but rather our ability to simulate it?

Line 802. Changes in NOx are cited here as a reason for discrepancy across the models. It’s clear from Figure S17 that there are differences across the models despite using the same anthropogenic emissions. It may help to refer back to this figure here, or give an example of the range in NOx concentrations over a region. This range could reflect different natural emissions, chemical or deposition lifetimes, or different mixing and transport (e.g. convection). Is it possible to rule out any of these processes?

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ED: Publish subject to minor revisions (review by editor) (25 Sep 2020) by Holger Tost

AR by Steven Turnock on behalf of the Authors (01 Oct 2020) Author's response Manuscript

ED: Publish as is (09 Oct 2020) by Holger Tost

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Short summary

A first assessment is made of the historical and future changes in air pollutants from models participating in the 6th Coupled Model Intercomparison Project (CMIP6). Substantial benefits to future air quality can be achieved in future scenarios that implement measures to mitigate climate and involve reductions in air pollutant emissions, particularly methane. However, important differences are shown between models in the future regional projection of air pollutants under the same scenario.