Dear Dr. Eley and co-authors,

Your manuscript received very thorough reviews from the two formal journal referees and comments from Jessica Tierney and Huan Yang. Thank you for the detailed responses to those comments, which indicate that you’ve given careful thought to the concerns and suggestions. Accordingly, I invite you to submit a revised version of the manuscript for further consideration.

Your responses explicitly mentioned how you intend to amend the manuscript in response to specific detailed comments. In your revised manuscript, I also encourage you to incorporate some of the nuance provided in your responses to the more general comments of reviewers. I further encourage you to reconsider the suggestion, made by two referees, to more fully detail applications of OPTiMAL to existing data (ie. including an application from Quaternary data, and including time series).

Given the complexity of the discussion and the broad potential interest in your manuscript, I will request that your revised manuscript goes through a second round of review. To do so requires that I indicate “reconsider after major revisions”.

Sincerely,
Alberto Reyes (handling editor)

Dear Dr. Eley and co-authors,

Your revised manuscript has now been reviewed by one of the original referees and Jessica Tierney, who provided a detailed public comment of the open Discussion paper. The reviews are positive on the direction of the manuscript. But one of the reviews raises several important points that warrant additional revision or consideration, with specific guidance on how you might address these concerns. I do not think this guidance is out of line, so I am recommending that you undertake additional revision of your manuscript. The following points seem especially pertinent:

1. Application examples: Several reviewers of the original manuscript suggested that you provide examples of OPTiMAL applications to downcore datasets. I agree that this is reasonable and seemingly standard for other TEX calibration papers (e.g. Kim et al. 2008, 2010; Tierney and Tingley, 2014).

2. Methodological clarity: Reviewers have provided specific recommendations for relatively minor manuscript re-organization that would enhance reader understanding of the methods and principles that underpin the approach.

I invite you to submit a revised manuscript that addresses the criticisms and suggestions from this second round of review. The revised manuscript will be assessed by an external referee, which requires that I indicate “reconsider after major revisions”.

Sincerely,
Alberto Reyes (handling editor)

Dear Dr Dunkley Jones and co-authors,
Your revised manuscript has now been reviewed by one of the original referees and one additional new referee. The original referee noted that the manuscript was improved by the additional discussion of GDGT metrics and that downcore data was a valuable addition to the manuscript. The new review by Peter Bijl provides constructive feedback for more nuanced framing of the manuscript, while acknowledging the potential importance and community interest in the work.

I'm recommending that the manuscript be published in Climate of the Past, pending your consideration of the points raised by Dr. Bijl in one more revised manuscript. When you submit the revised manuscript, please provide a brief response that outlines broadly any revisions or justifies any points that you don't feel warrant revision.

Sincerely,
Alberto Reyes

Dear Dr Dunkley Jones and co-authors,
Thank you for considering the comments of Dr. Bijl from this most recent round of reviews. I have gone over your responses and manuscript revisions, and it is with considerable pleasure that I recommend your manuscript be published in Climate of the Past. I thank you all for your patience and perseverance through this long review process.
Sincerely,
Alberto Reyes