Obliquity forcing of low-latitude climate

Bosmans, J. H. C.; Hilgen, F. J.; Tuenter, E.; Lourens, L. J.

doi:https://doi.org/10.5194/cp-11-1335-2015

Articles | Volume 11, issue 10

https://doi.org/10.5194/cp-11-1335-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/cp-11-1335-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 11, issue 10

Research article

|

09 Oct 2015

Research article |

| 09 Oct 2015

Obliquity forcing of low-latitude climate

J. H. C. Bosmans, F. J. Hilgen, E. Tuenter, and L. J. Lourens

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Final revised paper (published on 09 Oct 2015)
Preprint (discussion started on 11 Feb 2015)

Interactive discussion

Status: closed

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

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- Supplement

RC C26: 'What about high-latitude surface albedo changes?', Anonymous Referee #1, 18 Feb 2015
- AC C587: 'Author comments to reviewer 1', Joyce Bosmans, 10 Jun 2015
RC C265: 'Review of Obliquity forcing of low-latitude climate by Bosmans et al.,', Anonymous Referee #2, 22 Apr 2015
- AC C588: 'Author comments to reviewer 2', Joyce Bosmans, 10 Jun 2015

Peer-review completion

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

ED: Reconsider after major revisions (25 Jun 2015) by André Paul

AR by Joyce Bosmans on behalf of the Authors (06 Aug 2015)

ED: Referee Nomination & Report Request started (07 Aug 2015) by André Paul

RR by Anonymous Referee #2 (01 Sep 2015)

Suggestions for revision or reasons for rejection

The paper has strongly improved in the review process and I now recommend publication in Climate of the past after minor revisions.

My remaining comment concerns the still limited discussion about insolation and the insolation imprint in paleorecords as pointed out in my first review (third comment) and the comment (c) of the other reviewer.

Many aspects of the insolation forcing have essentially identical variability, and thus from just looking at the spectra of a record (especially just the amplitude ratio of precession and obliquity), many possible explanations remain (for an extreme example, see Huybers, Science 2009 which discusses an ice-core record but the same would apply to any geological record)

Classical 65N summer insolation + ice-sheet response + effect on low latitudes is one hypothesis, and using forward modeling, the presented study offers important insight in a more realistic alternative (as there was obliquity variability without ice-sheets). However, the the wider discussion of local hypotheses in the literature (e.g. Short et al., 1991, Laepple and Lohmann, 2009 who explicitly claim that one would expect obliquity from local forcing in the tropics) is not presented to the reader.

The authors argue that the Laepple and Lohmann, 2009, hypothesis can’t explain the obliquity signal as the amplitude would be too weak, but exactly this point would be the needed discussion for the reader to put the presented study in the context of the existing literature.

Huybers, Peter. „Antarctica’s Orbital Beat.“ Science 325, Nr. 5944 (28. August 2009): 1085–86. doi:10.1126/science.1176186.
Short, David A., John G. Mengel, Thomas J. Crowley, William T. Hyde, und Gerald R. North. „Filtering of Milankovitch cycles by Earth’s geography.“ Quaternary Research 35, Nr. 2 (1991): 157–73.
Laepple, Thomas, und Gerrit Lohmann. „Seasonal Cycle as Template for Climate Variability on Astronomical Timescales.“ Paleoceanography 24, Nr. 4 (1. Dezember 2009): PA4201. doi:10.1029/2008PA001674.

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RR by Anonymous Referee #1 (10 Sep 2015)

ED: Publish subject to minor revisions (review by Editor) (12 Sep 2015) by André Paul

AR by Joyce Bosmans on behalf of the Authors (22 Sep 2015) Author's response Manuscript

ED: Publish subject to technical corrections (28 Sep 2015) by André Paul

AR by Joyce Bosmans on behalf of the Authors (29 Sep 2015) Author's response Manuscript

Short summary

Our study shows that the influence of obliquity (the tilt of Earth's rotational axis) can be explained through changes in the insolation gradient across the tropics. This explanation is fundamentally different from high-latitude mechanisms that were previously often inferred to explain obliquity signals in low-latitude paleoclimate records, for instance glacial fluctuations. Our study is based on state-of-the-art climate model experiments.