Review for Karagodin-Doyennel et al., “The future ozone trends in changing climate simulated with SOCOLv4”, submitted to ACP

Here authors use the SOCOLv4 Earth System Model (ESM) to simulate future ozone evolution. Results from two model  simulations (based on two potential Shared Socioeconomic Pathways (SSP) scenarios: SSP2-4.5 and SSP5-8.5) are presented. SOCOL_v4 predicts a decline in tropospheric ozone around the 2030s for SSP2-4.5 and after  2060s under SSP5-8.5 scenarios primarily due to  decrease  in ozone precursors such as  NOx and CO. As expected, models also predict ozone increase in the upper/ middle stratosphere globally and high-latitude lower stratosphere. Model also predicts that under SSP5-8.5, the stratospheric ozone increases are largely due to stronger stratospheric cooling as more greenhouse gases lead to more cooling that slows ozone loss. On the other hand, both the simulations predict ozone decrease in the tropical lower stratosphere as strengthening of BD circulation transports more ozone to the mid-high latitudes. 

As confirmed by various recent studies, the model does not predict any decrease in lower stratospheric ozone at mid-latitudes. Consistent with our understanding, SOCOLv4 predicts an increase in stratospheric ozone in the 21st century due to decreases in the ODS and increases in the GHGs.

Overall, this is a well organised manuscript with some room for improvements. So I would recommend the manuscript for the publications if authors can address minor comments suggested below

1. I am struggling to find clear motivation. What are the largest sources of uncertainties in our understanding about the future evolution of ozone layer . What was done in earlier SOCOL studies and what was missing and how this manuscript is able to improve those biases. There are serveral papers like Morganstern et al., Dhomse et al., Keeble et al, highlighting the role of GHG in explaining decreases in tropical ozone. So, what is new here?
2. Why there is a paragraph about the VSLS if there are no plots showing its impact on the ozone layer?
3. Can you explain why sAOD term is included in DLM model though there is no volcanic eruption in the simulations
4. Line 198: Usage of DLM to model simulated data is still unclear. Please include some clear information explaining why this type of analysis should use DLM rather than multivariate (or ordinary least square) regression or simpler composite analysis. I strongly feel that using DLM for the analysis of observational data is OK as we have just one realisation about the past atmosphere. But as you have 3 ensemble members for each type of   simulation, does DLM provide unique insight in model world compared to simple averaging and smoothing?

Technical 

Line 115: Hu et al. (2015),

Line 163: Only GHGs (prescribed ODSs are identical)?

The MS: “The future ozone trends in changing climate simulated with SOCOLv4” deals with ozone evolution in the “middle-of-the-road” (SSP2-4.5) and “fossil-fueled” (SSP5-8.5) scenarios in the troposphere and middle atmosphere. As the authors have already presented the results from their historical simulations and comparisons to measurements in another paper, this study concentrates only on the future changes.

As expected, ozone is in increasing in the stratosphere and decreasing in the lower stratosphere and troposphere.  However, the mesospheric part is interesting as there are not many analyses for this region. This is a well-written MS and I have only some minor comments on this.

Major:

I thought a comparison between the previous RCP scenarios with the latest SSP scenarios is needed in the discussion. There are some studies based on CIMIP 5 ozone results.  This should be in the modelling point of view. You have mentioned some in Introduction, but a discussion of the ozone results from both CMIP5 and CIMP6 are needed.

Minor:

L6: “and upper and middle”

L9: speed up of BDC?

L11-12: increase of UV in the tropics or mid latitudes?

L20: element? You need a better word here

L31: The following studies should also be mentioned here

https://doi.org/10.5194/acp-18-7557-2018

https://doi.org/10.1038/s41612-018-0052-6

L38: GHG was first mentioned in L23

L84: space after full stop

L89: decrease (Keeble et al., 2021).

L102: what is “slightly“ comparable;?

L115: Hue et al. (2016)

L119: CCMI campaigns? Sounds a filed campaign, not modelling experiments

L168: respectively (Zhao et al., 2020)

L192: indices

L241, 245: delete content, use amount or concentration instead

L248: signs of increase

L251-252: how NOx produces ozone in the lower stratosphere?

L253: do not start a sent with AND

L260: These increases of 0.13 and 0.27 DU are significant?

L269: Can you please give another reference for this. It is known long before, not in 2021

L299: as expected

L369: delete the “expected”

L382: it barely changes? Then you write a change of -4DU/decade? Delete “barely”