Dear Dr Metcalfe

Thank you for your manuscript titled ‘On the validity of foraminifera-based ENSO reconstructions’ (manuscript #cp-2019-9) submitted for publication in Climate of the Past. The manuscript has received three referee reviews and one short comment during the Discussion phase.

After careful consideration of your Author Responses I regret to inform you that we are unable to accept the manuscript for publication at this time. The three referee reports and short comment are supportive of the FAMES approach, however they bring up similar issues on this specific manuscript, and fundamentally, there appears to be a mismatch between the intention of the study as read by the referees (and myself) in the submitted manuscript, and the intention of your study as stated in the Author Responses. The proposals for revision in the Author Response do not to my mind reconcile this key issue, nor adequately address the other major issues, and therefore I cannot accept the manuscript.

The detailed referee reports are made available for your reference and I encourage you to engage with these comments constructively in your future studies.

I wish to clarify for future reference that Climate of the Past referees are not required to cross-reference each other’s reports on the Discussions forum and are free to develop their reviews independently.

Again, thank you for your interest in the journal and I regret that I cannot be more positive on this occasion.

Yours sincerely,
Helen McGregor

Your paper received a number of quite negative reviews. Nonetheless, I have decided to allow you to prepare a new version (major revisions) for consideration by reviewers.

I accept that there is value in a paper that forward models the proxy record to assess whether ENSO characteristics are even recorded in forams, as opposed to an inverse model that seeks to determine ENSO from the foram record. Nonetheless, you should recognise that several well-qualified reviewers felt that your study had not met the targets expressed in the title and abstract. Rather than (as your responses tended to) berate them, I would like to see you improve your presentation and explanations so that readers are not left disappointed.

This applies also to other aspects of the paper: as an example, like some reviewers I found the figures and the different shadings hard to understand; please improve either the figures or the captions, which is more constructive than implying that the reviewers have been deficient in not being able to follow them.

In your responses you have raised a number of issues that you state were not part of your paper - for example bioturbation, and alternative statitsical methods. While I do not expect you to change your model or methodology completely to meet these concerns, you clearly do need to add paragraphs to your paper to state what might be the effect if these issues were covered, and why their lack does not affect your main findings.

I look forward to receiving a substantially improved paper for further review.

I have obtained two further reviews of your paper, both from referees who were not involved in the first round of reviewing. You will be relieved to know that both reviewers, in contrast to the previous rounds, do see merit in your approach - this means we have passed one barrier to publication. Referee 4 does not go into great detail after that, considering that your paper has already received a lot of comments. However referee 5 is very unhappy with the style of the paper and its readability, to the extent that they recommend rejection.

In view of the fact that we have votes in favour of the principle of the paper, and that I generally agree that this does seem like a useful approach, I have decided to let you proceed with a further revision. However I also agree with referee 5 that the paper is extremely tough going. As well as the review, referee 5 provided an annotated pdf with further comments and I am hoping Copernicus will load this for you to see soon. However the paper definitely needs yet another rewrite to make it easier to follow.
*The figures are called in a bizarre order (as far as I could see it went Fig 1, then 8 and 9, then in practice 5 and 7).
* The intro and methods are not too bad, but once we reach section 3, the paper needs to be structured in a logical and linear fashion so that the reader is guided from figure to figure and told what the conclusions from each one are. this is simply not the case at present and I could barely follow what you were doing.
*Additionally the density and number of figures is daunting. I strongly recommend that you strip down to a smaller number of essential panels and figures and put the rest into the supplement.

I realise this paper has already been through numerous iterations, but I'm afraid it is essential to make further improvements if it is to be accepted. I hope you will be able to achieve this.

Thank you for your further revision of this paper. You have made substantial changes to the paper after the last set of comments, and in particular the reorganisation of the paper into separate experiments has made the paper much easier to digest and understand. I am sure that if I sent the paper for re-review there would be further comments, but i think now we have taken the process as far as peer review can go: there would still be criticisms of your methodology, but your paper now contains enough caveats and explanations that a reader will be aware of the strengths and limitations of your approach. For that reason I have now decided to accept the paper without further review. Thank you for sticking with the process; I realise that it has been one that neither authors, reviewers or editors have enjoyed.

I have a small number of minor remaining comments that I'd ask you to address in your final version but I have decided hat they only constitute "technical" level correction. Please do look at these points though.

Page 8, line 5: Section starting "Though" isn't a sentence, please edit.
Fig 2 (and S6). Please expand on what you mean by "species specific results are overlain". Do you mean that in white areas all 3 species show a significant difference, or that at least one shows a significant difference. I think it's probably the latter, but the wording needs to make this clear.
Page 13, line 25 "studies reliant have used" doesn't make sense, please edit.
Page 14. This section is very hard to read (a long list of numbers). I don't have specific suggestion but can it be simplified at al?
Table 1 and Fig 3b. The values labelled as "% difference" are actually neither percent (values between 0 and 100) nor differences, rather they are ratios. Please re-label.
Section 6 (expt 4) is really not very clear and I suspect adds little to the paper. However in the spirit that in the end it's your paper, and that others may be able to build the idea in it, I am not proposing any change.