Hazards of decreasing marine oxygen: the  near-term and millennial-scale benefits  of meeting the Paris climate targets

Battaglia, Gianna; Joos, Fortunat

doi:https://doi.org/10.5194/esd-9-797-2018

Articles | Volume 9, issue 2

https://doi.org/10.5194/esd-9-797-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

The Earth system at a global warming of 1.5°C and 2.0°C

https://doi.org/10.5194/esd-9-797-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 9, issue 2

Research article

| Highlight paper

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13 Jun 2018

Research article | Highlight paper |

| 13 Jun 2018

Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets

Gianna Battaglia and Fortunat Joos

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Final revised paper (published on 13 Jun 2018)
Preprint (discussion started on 01 Nov 2017)

Interactive discussion

Status: closed

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

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RC1: 'Review', Anonymous Referee #1, 19 Nov 2017
- AC1: 'Response', Gianna Battaglia, 08 Feb 2018
RC2: 'Review', Anonymous Referee #2, 02 Dec 2017
- AC1: 'Response', Gianna Battaglia, 08 Feb 2018

Peer-review completion

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

ED: Reconsider after major revisions (09 Feb 2018) by Axel Kleidon

AR by Gianna Battaglia on behalf of the Authors (10 Feb 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (13 Feb 2018) by Axel Kleidon

RR by Andreas Oschlies (16 Feb 2018)

Suggestions for revision or reasons for rejection

The authors have substantially rewritten their manuscript and satisfactorily addressed many of the concerns raised in my earlier review. Overall, the paper is more focused and shows very interesting and new scientific results about long-term ocean deoxygenation. These should be published. The link to the Paris agreement is, however, still weak and confusing. In the model, three time points are investigated: year 2100, the time of peak change o a variable, and the model’s equilibrium response around year 8000. The official text of the Paris agreement does not refer to a specific time, and it would be helpful to clearly state which time the authors refer to when speaking about an X degree climate target or, even specifically, the climate targets of the Paris agreement (e.g. p.2, l.24). On p.4,l.23 the authors cite text from the UNFCCC web page that, in contrast to the Paris agreement, describes temperature targets as targets for THIS CENTURY. This is an interesting deviation from the official document. In order to avoid more confusion, the authors should take the opportunity to state more clearly what times they refer to. They mostly seem to refer to equilibrium warming, which, however, would be in conflict with their above reading of the Paris agreement.

individual points:

p.5, l.4 are equilibrium changes always ‘larger’ ?
p.5 l.5 what is the time stamp of global warming here?

p.5, l.31 It is not clear what is meant by ‘linear’. Linear in time, in the equilibrium temperature?
p.5, l.32 time stamp of \Delta SAT ?

p.10,l.23 ‘correlates’ is difficult to see from Fig.2 - all curves somehow correlate with each other. Describe more clearly what you mean.

p.12 Fig 1c,d. Mention whether these are annual mean or summer ice areas.

p.16, l.31 should probably refer to Fig.5a

p.23, l.13. 320 GtC post-2017 emissions would be a larger carbon budget for the 1.5C target than implied by the last IPCC AR5, I think. I looked up the Steinacher et al. (2013) paper, but could not find this number.

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RR by Andreas Schmittner (27 Feb 2018)

ED: Reconsider after major revisions (07 Mar 2018) by Axel Kleidon

AR by Gianna Battaglia on behalf of the Authors (13 Apr 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 Apr 2018) by Axel Kleidon

RR by Andreas Oschlies (15 May 2018)

ED: Publish as is (15 May 2018) by Axel Kleidon

AR by Gianna Battaglia on behalf of the Authors (22 May 2018)

Short summary

Human-caused, climate change hazards in the ocean continue to aggravate over a very long time. For business as usual, we project the ocean oxygen content to decrease by 40 % over the next thousand years. This would likely have severe consequences for marine life. Global warming and oxygen loss are linked, and meeting the warming target of the Paris Climate Agreement effectively limits related marine hazards. Developments over many thousands of years should be considered to assess marine risks.