Dear authors,

Thank you for submitting your responses to the reviewer comments that you received on your manuscript and for submitting a revised version. I would also like to thank the reviewers for their constructive feedback and comments, some of which were common between them, and leading to a more in-depth analysis of the forcings and feedback parameters in the two versions of the EC-Earth model analysed here.

Having read the reviewer comments and your responses to them, I make the following observations:

1. Reviewer #1 commented on the need for careful documentation in response to your sentence that it is difficult to turn back or switch off developments in a systematic way. While I accept that EC-Earth is a consortium model and some developments may be outside of your control, I wonder whether the current experience with changes in ECS from one version of EC-Earth to another may lead to a change in model development strategy? Are there valuable lessons to be learnt from this that might inform the model development process more generally? Given this may be relevant to other models, could I ask you to add a relevant comment? It would also help to address the reviewer’s comment further.
2. In response to Reviewer #1, could I please ask you to provide a very brief explanation for effective radius, auto conversion-efficiency, and activation scheme? While you may not feel it is necessary, if this reviewer felt an explanation was warranted, there may well be other readers of your manuscript that share that view. This could be placed in a short appendix if you thought that it may affect the flow and focus of the relevant section.
3. Reviewer #1 and missing references: While I cannot speak for the reviewer, looking at the lines referred to, I think the reviewer is just asking to add some (or more) justification/support for your statements. Here are some suggestions:
• Line 62: Please add references for CMIP5 and CMIP6 forcings (e.g. Meinhausen et al., Hoesly et al., etc..)
• Line 110: Here I think the reviewer is referring to the challenge of running a coupled model to equilibrium. Can you include references to papers that also refer to this challenge in support of your statements from lines 108-112?
• Line 113: Likewise, is there evidence from other studies that demonstrate that the Gregory approach is a suitable alternative?
• Line 124: Can you provide examples of other studies that divide by 2? I know this is common practice but again, it’s just to provide additional support for the approach taken.
4. Reviewer #2: Use of CMIP variable names. I have to agree with the reviewer here and ask that you change names like tas to near-surface temperature.

Otherwise, I am happy that you’ve adequately addressed the reviewer comments and once you’ve addressed the minor comments above, I will recommend that your manuscript be accepted for publication.

Regards,
Fiona O’Connor