Climate and stratospheric ozone during the mid-Holocene and Last Interglacial simulated by MRI-ESM2.0

Watanabe, Yasuto; Deushi, Makoto; Yoshida, Kohei

doi:10.5194/cp-21-2243-2025

Articles | Volume 21, issue 11

https://doi.org/10.5194/cp-21-2243-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/cp-21-2243-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 11

Research article

|

17 Nov 2025

Research article |

| 17 Nov 2025

Climate and stratospheric ozone during the mid-Holocene and Last Interglacial simulated by MRI-ESM2.0

Yasuto Watanabe, Makoto Deushi, and Kohei Yoshida

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Final revised paper (published on 17 Nov 2025)
Preprint (discussion started on 30 Jan 2025)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-4162', Anonymous Referee #1, 18 Mar 2025

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2024-4162/egusphere-2024-4162-RC1-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2024-4162-RC1
- AC1: 'Reply on RC1', Yasuto Watanabe, 09 Jun 2025
  
  We appreciate the reviewer for the thoughtful review. Please find our response in the attached Supplement PDF file.
  
  Citation: https://doi.org/10.5194/egusphere-2024-4162-AC1
CC1:
'Comment on egusphere-2024-4162', Jo-Jo Eumerus, 16 Apr 2025

A few minor observations:

* Are there any data that identify causal mechanisms e.g are the ozone and temperature changes solely due to local insolation and sea ice or are there atmospheric circulation changes (perhaps sector-dependent) that also play a role?
* In Fig3, it seems like MH and LIG have opposite temperature changes in Antarctica during JJA; any indication why?
* Has ozone effects on climate just in Antarctica?

Citation: https://doi.org/10.5194/egusphere-2024-4162-CC1
- AC3: 'Reply on CC1', Yasuto Watanabe, 09 Jun 2025
  
  We appreciate Jo-Jo Eumerus for providing valuable comments on our manuscript. Please find our response in the attached Supplement PDF file.
  
  Citation: https://doi.org/10.5194/egusphere-2024-4162-AC3
RC2:
'Comment on egusphere-2024-4162', Anonymous Referee #2, 12 May 2025

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2024-4162/egusphere-2024-4162-RC2-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2024-4162-RC2
- AC2: 'Reply on RC2', Yasuto Watanabe, 09 Jun 2025
  
  We appreciate the reviewer for the thoughtful review. Please find our response in the attached Supplement PDF file.
  
  Citation: https://doi.org/10.5194/egusphere-2024-4162-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

ED: Reconsider after major revisions (14 Jun 2025) by Laurie Menviel

AR by Yasuto Watanabe on behalf of the Authors (09 Aug 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (11 Aug 2025) by Laurie Menviel

RR by Anonymous Referee #3 (25 Sep 2025)

Suggestions for revision or reasons for rejection

The paper by Watanabe and co-authors present simulations of the effects of Earth’s orbital variations on climate with a focus on how ozone may affect the ability of models to reproduce the reconstructed climate of the mid-Holocene (MH) and Last Interglacial (LIG) warm periods. The analysis builds on, and in some aspects conflicts with, previous work (Noda et al., 2017) that used an earlier version of the MRI model but only looked at the MH. The authors find some significant and physically consistent changes in ozone, temperature and winds in the stratosphere but the impact in the troposphere and, in particular, on the surface climate are relatively modest.
I was not one of the reviewers for the first submitted version of the paper, nor have I read that version. I have, however, read the comments from the reviewers (after having read the current version) and feel that the revisions to the structure and presentation of the results may have gone some way to address the concerns from reviewer 2 of the first version. I certainly did not have similar concerns about the presentation when reading the paper.
My one significant concern about the discussion of the results centers around the near-surface wind response around the South Pole shown in Figure 9 and discussed starting around line 239. Particularly striking is the seasonal change in the response, with strong positive anomalies for the LIG simulation in JJA-SON, and strong and relatively symmetric weakening in DJF and MAM. I can see the physical explanation for the acceleration of the near-surface winds for JJA and SON being connected to similar signed changes in the stratosphere in a way that is quite analogous with what is seen for ozone depletion since the 1980s. But the changes in DJF and MAM are much harder to connect with the temperature changes that have been presented. The seasonal cycle of temperature change at 3hPa (Figure 3) does not show much of a change in temperature gradient across the mid-to-high latitudes of the Southern Hemisphere for DJF and MAM so I suspect there is some change in temperature that is not apparent in the figures that is driving the weakening of the winds. I would like to see just a little bit more supporting information or discussion to provide an explanation for the strong seasonal behaviour of the impact on the near-surface winds around the Antarctic.
My other comments are minor and are itemized below.
Line 57 – this study extends previous study of Noda et al., (2017) that used MRI-ESM1 to investigate ozone effects during the MH.
Lines 57 – 62: The section beginning ‘This study showed that the positive ozone…’ through to ‘…different astronomical forcing during the MH.’ has a few instances of repetition that could be removed to make it a bit easier reading.
Lines 89 – 90: The MH and LIG simulations started ‘from the steady state obtained for the MH condition submitted to PMIP4.’ It is not quite clear what the ‘steady state’ from the PMIP4 simulation is. I assume the simulations presented here start from the model state after the first 51 years of spin-up for the PMIP4 simulation, but as the authors have explained this is not necessarily a steady state.
Line 101 – Table 1: In the greenhouse gas column there is reference to NO2, but I am certain this is a typo and should be N2O.
Lines 118 – 126: The discussion of the temperature effects on ozone needs to be strengthened. I am most familiar with the temperature effects due to changes in CO2, for which the impacts on ozone through the temperature sensitivity of ozone loss reactions is well known. Here the irradiance is changing so in addition to the temperature effects on O3 + O -> 2O2, there would be changes on O2 and O3 photolysis. Given the strong anti-correlation of temperature and ozone changes, I am not doubting that the temperature effect dominates only that the discussion is a bit underdeveloped.
Line 152 – Figure 4: The presentation of annual mean zonal cross section changes really dilutes the impacts of the changes. The seasonal cycle of changes at 3hPa shown in Figure 3 has the LIG simulation with much larger changes than those seen for the MH, but in the annual average these appear weaker. In particular, the strong positive changes in temperature seen near the north pole in JJA for Figure 3d are now negative in the annual average shown in Figure 4b. Is the manuscript losing important aspects of the response by presenting annual average changes? Because of the nature of the changes in forcings I can appreciate that it is not as simple as showing JJA and DJF – the insolation anomaly in the MH maximizes in JJA over the northern high latitudes but in SON for high southern latitudes.
Line 170: The use of the word ‘transported’ in ‘This signal was transported into the lower stratosphere.’ seems to suggest there was advection of the warm anomaly seen earlier in the year at lower pressure downwards. I think this is difficult to justify. The warm anomaly does seem to follow the ozone anomaly, so I would think it is more of a perturbation of local heating rates.
Lines 176– 183: The authors might make it clearer that the discussion is focusing on the differences between the differences in the full simulations and the nochem simulations.
Lines 233 – 236: I believe I understand the explanation the authors are suggesting for the acceleration of the southern westerly jet. If I do, the authors could make reference to Figure 3c and 3d to show the stronger meridional temperature gradient driven by warming on the equator-ward side of the jet that is responsible for the acceleration.
Lines 299 – 300: Similar to the comment on line 170 about the use of ‘transported’ when discussing temperature anomalies, is it the temperature transported or the ozone anomaly that carries along with it a heating rate anomaly?
Line 301: The statement ‘possibly reflecting the modulation of the Arctic Oscillation.’ seems unsupported by analysis. And I am not sure what the authors wish to imply with this statement.
Line 303: ‘This ozone-induced expansion of sea ice…’ The caption for Figure 13 states that the dashed line is the sea-ice edge for the PIcontrol, while the solid line is for the MHcontrol or LIGcontrol experiment. When you look closely at Figure 13g, the dashed and solid line seems to suggest that the sea-ice has retreated in the Atlantic side of the Arctic between PIcontrol and LIGcontrol, but the ozone related temperature changes are negative. The idea that the ozone-driven cooling is partly counteracting an insolation-driven warming is supported by Figure 12. But then can it be deduced that the ozone-driven changes are also responsible for counteracting some of the sea-ice retreat?
Line 311: Figure 12 is for the North pole but the caption has ‘at the tropic region (60–90˚N)’.

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ED: Publish subject to minor revisions (review by editor) (29 Sep 2025) by Laurie Menviel

AR by Yasuto Watanabe on behalf of the Authors (16 Oct 2025) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (20 Oct 2025) by Laurie Menviel

AR by Yasuto Watanabe on behalf of the Authors (21 Oct 2025) Manuscript

Short summary

This study uses an Earth System Model, MRI-ESM2.0, to demonstrate that the atmospheric ozone distribution during warm interglacial periods is modified by the changes in the Earth's orbital parameters. We further show that the change in atmospheric ozone works to cool the surface at the high-latitude regions of the northern hemisphere in the past warm interglacial periods (6 and 127 thousand years ago), while its impact is small around Antarctica.