Dear authors,

The reviewers are broadly satisfied with your revised manuscript, although both recommend some minor revisions, copied below. Please address these points and I will take a decision on the final revised manuscript, which should be a straightforward acceptance.

Apologies for some delay in the editorial process, due to my considerable "day job" commitments.

Best Regards,
Bob Marsh


Referee #1

The authors have made considerable changes and improvements to this manuscript after the first set of reviews. There is now a lot more information, fuller discussion of the results in the context of previous work, and more figures.

I think the authors have satisfactorily responded to most of the reviewer comments. There are still some issues that need to be addressed, most of which are fairly minor.

1. The authors state in the responses to the reviewer comments regarding the link between sea ice loss and storminess: “However, as the main focus in this manuscript is on representation of storminess in NorESM in historical and future climate, we consider such an analysis outside the scope of this study.”
Based on this and the title of the paper, I wonder why the first paragraph of the introduction to the paper is all about sea ice loss. I think the introduction needs to be restructured to introduce the most important aspect first. The sea ice loss may then motivate the region of focus.
2. I find that having a “Results and discussion” section rather than “Results”, then “Discussion” makes the results hard to follow. I would suggest restructuring this section somewhat, to present the results in a simple way, then have a section discussing the context and comparison with other studies and the implications of the results. An example is the second paragraph of section3, where the discussion of the comparison with Catto et al and Zappa et al might be better later.
3. Line 57: “decreasing September sea ice edge” might be better as “retreating September sea ice edge” or “decreasing sea ice edge extent.
4. Lines 83-95: There are also energetic arguments for the changes (see O’Gorman and Schneider (2008) for a good additional reference here).
5. Section 2: This section would be much easier to read if there were some subheadings, such as “Models”, “Sea Ice Data”, “Methods”.
6. Lines 159-174: Can you say somewhere in this section what the difference between sea ice concentration and sea ice extent is, how are each of them used in the study, and from which datasets?
7. Lines 180-182: These lines could be made clearer. Is it that the vorticity method identifies more cyclones than a SLP method, but there are other methods that identify even more cyclones?
8. Line 208: There are more recent polar low climatologies that you could also include here – Yanase et al (2016) and Zappa et al.
9. Line 227: The intermediate scenario in that study was a 2XCO2 idealized scenario, which is different to the scenarios investigated here. This would be worth noting and bearing in mind.
10. Line 231: It is not clear what is meant by “diverging” here.
11. Section 3: It gets quite confusing jumping between the main figures and the appendix figures. Would it be possible to have the extra figures as part of the body of the manuscript?
12. Lines 273-276: This jumps around between sea ice concentration and sea ice extent, which is quite confusing.
13. Line 279: “discrepancy” would be clearer as “positive bias”.
14. Line 283: “The signal…” of what?
15. Line 311: Please be clear what is meant by “coherent”.
16. Line 374-376: Catto et al 2015 also showed that the precipitation biases are larger for light precipitation, but heavier frontal precipitation is well represented.
17. Section 3.2: When giving the percentage changes for September and December in brackets, it would be good to make it clear that this is what they refer to (at least the first time).
18. Line 435: “While more cyclones are expected…” Why is this expected?
19. Line 491: “thus foster the cyclones.” Are you saying this is the cyclogenesis mechanism? I don’t think the word “foster” is a good one here – it is not clear what is meant.
20. Line 529: Have you seen in your data a decrease equatorward of 40 degrees N? If you have seen it but are not showing it in a figure, I would just say “not shown”. If you haven’t seen it, I would remove this.
21. Section 4: The first two bullet points of the conclusions are related to sea ice. Again, since the focus of this paper is on the storminess, these bullet points need to be revised.
22. Line 616: “where cyclones foster from…” should be “where cyclones are generated by…” or something similar.

References:

Catto, J. L., C. Jakob, and N. Nicholls (2015), Can the CMIP5 models represent winter frontal precipitation?, Geophys. Res. Lett., doi: 10.1002/2015gl066015.

OGorman, P. A., and T. Schneider (2008), Energy of midlatitude transient eddies in idealized simulations of changed climates, Journal of Climate, 21 (22), 5797–5806, doi:10.1175/2008JCLI2099.1.

Yanase, W., H. Niino, S.-I. I. Watanabe, K. Hodges, M. Zahn, T. Spengler, and I. A. Gurvich (2016), Climatology of polar lows over the Sea of Japan using the JRA-55 reanalysis, J. Climate, 29, 419–437, doi:10.1175/JCLI-D-15-0291.1.

Zappa, G., L. Shaffrey, and K. Hodges (2014), Can polar lows be objectively identified and tracked in the ecmwf operational analysis and the era-interim reanalysis?, Monthly Weather Review, 142 (8), 2596–2608, doi:10.1175/MWR-D-14-00064.1.


Referee #2

General Comments:
The authors have carefully revised the manuscript based on the reviewers’ comments and replied adequately to all inquiries. The manuscript has improved greatly during revision and is now close to publishable form. I have included a number of minor comments below to help the authors further improve the manuscript.

Minor Comments:
# 1: Page 1, line 15-17: “… and sea level and the loss of ice …” please rephrase.

# 2: Page 7, lines 203. “clearly incapable” is a very strong statement. Maybe “have strong difficulties” or “strongly underestimate” would be more adequate. Please rephrase.

# 3: Page 7, line 225: The results are partly in contrast with Catto et al (2011) because they analysed scenarios with a stronger forcing (4xCO2 I believe). This should be stated.

# 4: Page 9 line 283: “the signal” it should actually be “the bias”, please rephrase.

# 5: Page 9 lines 289-291: This is purely speculative I suggest deleting the sentence.

# 6: Page 11, line 345: I suggest adding “assumed to be” after “is”, like “orographic precipitation is assumed to be the …”

# 7: Page 11, line 367: Please change “has” to “may have”.

# 8: Page 12, lines 380-383: These sentences read somewhat confusing please rephrase.

# 9: Page 13, line 440: Please change “generation” to “genesis”

# 10: Page 13, line 445: Please change “too” to “also”

# 11: Page 14, lines 478-480: This is quite speculative I suggest deleting the sentence.

# 12: Page 15, lines 500-502: This is speculative I suggest deleting the sentence or at least rephrasing it.

# 13: Page 16, lines 521-522: This is somewhat speculative as the changes may not be statistically significant. Please rephrase.

# 14: Page 17, line 573: Please change “are relatively small too” to “are also relatively small”

# 15: Page 17, line 587: How much are these values compared to the total annual precipitation for each model?

# 16: Page 18, line 596: The correct statement would be “due to data availability”.

# 17: Page 18, lines 604-606: Please rephrase at best with two sentences.

# 18: Page 18, line 611: “sea level pressure values”

# 19: Page 19, lines 624-625: Why should they correlate proportionally to cyclone intensity??

# 20: Figures: Figure numbers are strange, A - E and 1 - 8, etc please check

Dear authors,

I am satisfied with your thorough responses to both reviewers, and the final revised manuscript. Specifically, I accept your preference for a combined "Results and Discussion" section, rather than separation of Results and Discussion.

One minor comment from me, for your consideration:
Line 162: Rather than "... have strong difficulties of capturing ...", I suggest the phrase "... struggle to capture ..."

Thank you for persevering with a long review process. I hope you are satified with the eventual outcome, after all the revisions. Congratulations!

Best Regards,
Bob Marsh