Objective extraction and analysis of statistical features of Dansgaard–Oeschger events

Lohmann, Johannes; Ditlevsen, Peter D.

doi:https://doi.org/10.5194/cp-15-1771-2019

Articles | Volume 15, issue 5

https://doi.org/10.5194/cp-15-1771-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/cp-15-1771-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 5

Research article

|

27 Sep 2019

Research article |

| 27 Sep 2019

Objective extraction and analysis of statistical features of Dansgaard–Oeschger events

Johannes Lohmann and Peter D. Ditlevsen

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Final revised paper (published on 27 Sep 2019)
Supplement to the final revised paper
Preprint (discussion started on 25 Feb 2019)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of paper “Objective extraction and analysis of statistical features of Dansgaard-Oeschger events” by J. Lohmann and P. Ditlevsen', Anonymous Referee #1, 16 Apr 2019
- AC1: 'Response to RC1', Johannes Lohmann, 16 May 2019
RC2: 'Review of Lohmann and Ditlevsen (2019)', Anonymous Referee #2, 18 Apr 2019
- AC2: 'Response to RC2', Johannes Lohmann, 16 May 2019
AC3: 'Author's response to reviews', Johannes Lohmann, 16 May 2019

Peer-review completion

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

ED: Reconsider after major revisions (25 May 2019) by Barbara Stenni

AR by Johannes Lohmann on behalf of the Authors (31 May 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (07 Jun 2019) by Barbara Stenni

RR by Anonymous Referee #2 (08 Aug 2019)

Suggestions for revision or reasons for rejection

Review of revised manuscript: “Objective extraction and analysis of statistical features of Dansgaard-Oeschger events”

First, I want to apologize to the authors for the time it has taken to complete this review. I was away on vacation and for scientific meetings.

Below is a list of some of the changes that I think are necessary for publication – all of which were already in my first review. The authors take a different view on what the words “control” and “determine” mean than I do. The majority of readers will be interested in DO climate dynamics and physics rather than statistics, and so these words need to be changed to bring them into alignment with how the majority of readers would understand them.

The authors still confuse causation with correlation. In the old manuscript they claim that cooling rates “control” the interstadial durations – in reality they are merely correlated. In the revised manuscript they have simply changed the word “control” into “govern”. This is unacceptable. Simply changing a word does not solve the underlying scientific fallacy. There is no mechanistic link given by which cooling rates control/govern the interstadial duration. More likely, both are controlled by a third parameter. The authors concede this point. This must be corrected, because both words imply (mechanistic) causality, which is not proven or even made plausible. The authors suggest that their words must be interpreted in a statistical context. I am note entirely sure what that means, but to the majority of readers this will not be how they interpret the word “govern”.

The authors maintain that it is conceivable that the interstadial duration is “determined” hundreds to thousands of years ahead of time. The correct word here is “can be predicted”. They give an example of walking towards a town at a fixed rate. My arrival time can be predicted once my speed is known, but it is not yet “determined”. I could decide to take a 1 hour coffee break. The outcome of a democratic election can be *predicted* by polling the voters, it is not yet *determined* by this process. Likewise, once several hundred years have elapsed within an interstadial, the cooling rate can be estimated reliably, which means the duration of that interstadial can be *predicted* because the cooling rate is *correlated* with the duration (it does *not* control/govern it). This does not mean that the duration is already determined – volcanic eruptions, ice shelf collapse, or any number of things could happen that influence the true duration.

The discussion section is still just a summary of the work, now with a single paragraph of true discussion added (last one). This is not the function of a discussion section.

The authors have not attempted to shorten the paper. I still think this is appropriate, but I’ll leave this up to the editor.

Data availability. The authors are not compliant with the CP data policy, which states that “Copernicus Publications requests depositing data that correspond to journal articles in reliable (public) data repositories, assigning digital object identifiers, and properly citing data sets as individual contributions.” The 5yr data series should be publicly archived in a long-term database. These data have been used in several papers now, and requiring readers to contact a colleague of the authors (who is close to retirement age and not known for his reliability in responding to email) is not an acceptable form of archiving.

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ED: Publish subject to minor revisions (review by editor) (15 Aug 2019) by Barbara Stenni

AR by Johannes Lohmann on behalf of the Authors (21 Aug 2019) Author's response Manuscript

ED: Publish as is (31 Aug 2019) by Barbara Stenni

AR by Johannes Lohmann on behalf of the Authors (02 Sep 2019)

Short summary

Greenland ice core records show that the climate of the last glacial period was frequently interrupted by rapid warming events, followed by cooling episodes of vastly different duration. We fit a generic waveform to the noisy ice core record in order to extract a robust climate signal and empirically study what controls the amplitude and duration of the warmings and coolings. We find that cooling transitions are more predictable than warmings and are influenced by different climate forcings.