Emergent constraints on equilibrium climate  sensitivity in CMIP5: do they hold for CMIP6?

Schlund, Manuel; Lauer, Axel; Gentine, Pierre; Sherwood, Steven C.; Eyring, Veronika

doi:https://doi.org/10.5194/esd-11-1233-2020

Articles | Volume 11, issue 4

https://doi.org/10.5194/esd-11-1233-2020

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

https://doi.org/10.5194/esd-11-1233-2020

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

Articles | Volume 11, issue 4

Research article

| Highlight paper

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21 Dec 2020

Research article | Highlight paper |

| 21 Dec 2020

Emergent constraints on equilibrium climate sensitivity in CMIP5: do they hold for CMIP6?

Manuel Schlund, Axel Lauer, Pierre Gentine, Steven C. Sherwood, and Veronika Eyring

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Final revised paper (published on 21 Dec 2020)
Preprint (discussion started on 17 Jul 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Schlund review', Peter Caldwell, 19 Aug 2020
- AC1: 'Reply to Peter Caldwell (Referee)', Manuel Schlund, 26 Sep 2020
RC2: 'Review', Thorsten Mauritsen, 25 Aug 2020
- AC2: 'Reply to Thorsten Mauritsen (Referee)', Manuel Schlund, 26 Sep 2020

Peer-review completion

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

ED: Reconsider after major revisions (28 Sep 2020) by Christoph Heinze

AR by Manuel Schlund on behalf of the Authors (12 Oct 2020) Manuscript

ED: Referee Nomination & Report Request started (15 Oct 2020) by Christoph Heinze

RR by Thorsten Mauritsen (31 Oct 2020)

Suggestions for revision or reasons for rejection

Second review of "Emergent constraints on equilibrium climate sensitivity in CMIP5: do they hold for CMIP6?" but Manuel Schlund and co-authors.

Overall, I am happy with the revisions undertaken by the authors based on my first review. I have a few comments of minor nature that should be addressed prior to publication.

Sincerely,
Thorsten Mauritsen

24, replace 'increased' -> 'widens'
24-25, I think the text in parentheses is confusing, I recommend deleting
30-33, I am not sure I understand this text, I recommend revising. As it stands it seems to suggest that the emergent constraints that are process-based (those in this study except COX) are superior in constraining ECS to those that more directly constrain ECS using global change (Hargreaves 12+16, Jimenez 19, Tokarska 20, Renoult 20 etc.).
94, Leakage is normally compensated for by subtracting imbalance from the control simulation. I think the authors do this.
96-97, You might specify that these 6 percent is a model-based estimate of the compensation between changing feedback with time and the difference in ECS estimated by 2xCO2 and 4xCO2 (2x2 < 4).
144-145, I don't understand the meaning of this? Isn't the whole purpose of emergent constraints to utilise variations in model performance to better constrain something of interest?
404-405, replace 'not suffer from the same' -> 'overcome this'
411, a matter of tone, but I suggest replacing 'However' -> 'Nevertheless'
413-414, In my first review I provided a possible explanation for this, i.e. that it is to be expected that models with higher ECS will yield this result. I am not sure that writing in this way provides the reader with an appropriate impression of the other studies mentioned in the paragraph.
432-433, see comments on 24-25.

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RR by Peter Caldwell (03 Nov 2020)

ED: Publish subject to minor revisions (review by editor) (03 Nov 2020) by Christoph Heinze

AR by Manuel Schlund on behalf of the Authors (10 Nov 2020) Author's response Manuscript

ED: Publish subject to technical corrections (13 Nov 2020) by Christoph Heinze

AR by Manuel Schlund on behalf of the Authors (13 Nov 2020) Author's response Manuscript

Short summary

As an important measure of climate change, the Equilibrium Climate Sensitivity (ECS) describes the change in surface temperature after a doubling of the atmospheric CO₂ concentration. Climate models from the Coupled Model Intercomparison Project (CMIP) show a wide range in ECS. Emergent constraints are a technique to reduce uncertainties in ECS with observational data. Emergent constraints developed with data from CMIP phase 5 show reduced skill and higher ECS ranges when applied to CMIP6 data.