Climate engineering to mitigate the projected 21st-century terrestrial drying of the Americas: a direct comparison of carbon capture and sulfur injection

Xu, Yangyang; Lin, Lei; Tilmes, Simone; Dagon, Katherine; Xia, Lili; Diao, Chenrui; Cheng, Wei; Wang, Zhili; Simpson, Isla; Burnell, Lorna

doi:https://doi.org/10.5194/esd-11-673-2020

Articles | Volume 11, issue 3

https://doi.org/10.5194/esd-11-673-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Resolving uncertainties in solar geoengineering through multi-model...

https://doi.org/10.5194/esd-11-673-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 11, issue 3

Research article

|

31 Jul 2020

Research article |

| 31 Jul 2020

Climate engineering to mitigate the projected 21st-century terrestrial drying of the Americas: a direct comparison of carbon capture and sulfur injection

Yangyang Xu, Lei Lin, Simone Tilmes, Katherine Dagon, Lili Xia, Chenrui Diao, Wei Cheng, Zhili Wang, Isla Simpson, and Lorna Burnell

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Final revised paper (published on 31 Jul 2020)
Preprint (discussion started on 28 Jan 2020)

Interactive discussion

Status: closed

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

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RC1: 'Comments to the paper', Anonymous Referee #1, 24 Feb 2020
- AC1: 'Response to Reviewer #1', CHENRUI DIAO, 01 Jun 2020
RC2: 'Review', Anonymous Referee #2, 24 Feb 2020
- AC2: 'Response to Reviewer #2', CHENRUI DIAO, 01 Jun 2020
RC3: 'comment on Climate engineering to mitigate the projected 21st-century terrestrial drying of the Americas: Carbon Capture vs. Sulfur Injection', Anonymous Referee #3, 01 Mar 2020
- AC3: 'Response to Reviewer #3', CHENRUI DIAO, 01 Jun 2020

Peer-review completion

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

ED: Publish subject to minor revisions (review by editor) (05 Jun 2020) by Govindasamy Bala

Editor Comments:
The following comments are on the original submission.
1. I see that most of the comments of the reviewers are addressed. However, responses are given only to the reviewer for some of the comments and not addressed in the manuscript. I suggest the authors to address every comment in the manuscript.
2. Table 2, caption: Discuss the numbers in the parenthesis.
3. Tables 2, 4 and 5: Uncertainty estimates are missing in the current tables. It is important to provide them.
4. Fig. 2 caption: suggest to change “dashed regions” to “stippling”. Also, indicate the significance level in the caption, e.g. 5% or 10% significance level.
5. Figure 9: The top 3 panels are missing in the submitted file.
6. Figure 9, Caption: “Row a (left) is the changes in the baseline warming. Row (b) is the mitigated change due to carbon capture. Row (c) is the mitigated change due to sulfur injection” should be changed to “Left panels show the changes in baseline warming simulations, middle panels show the changes due to carbon capture and right panels show the changes due to sulfur injection”
7. Lines 540-560, the differing slopes for P change: This is related to the differences in the fast adjustments to the CO2 and stratospheric SO4 aerosol (or solar) forcings. If the P changes related to fast adjustments are removed, then the slope in the two cases should be similar. A rich literature exists on this topic. You can discuss the role of fast adjustments in these differences and cite the following papers. I do understand that you would need fixed-SST experiments to diagnose these fast adjustment P changes.

G. Bala, P. B. Duffy, and K. E. Taylor, 2008: Impact of geoengineering schemes on the global hydrological cycle, Proceeding of the National Academy of Sciences, 105(22), 7664-7669
G. Bala, K. Calderia, R. Nemani, 2009: Fast versus slow response in climate change: Implication to the global hydrological cycle, Climate Dynamics, DOI 10.1007/s00382-009-0583-y

Duan, Long Cao, G. Bala and K. Caldeira, 2018: Comparison of the Fast and Slow Climate Response to Three Radiation Management Geoengineering Schemes, J. Geophys. Res. -Atmos., 10.1029/2018JD029034

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AR by Yangyang Xu on behalf of the Authors (09 Jun 2020) Author's response Manuscript

ED: Publish as is (02 Jul 2020) by Govindasamy Bala

Short summary

Two geoengineering schemes to mitigate global warming, (a) capturing atmospheric CO₂ and (b) injecting stratospheric sulfur gas, are compared. Based on two sets of large-ensemble model experiments, we show that sulfur injection will effectively mitigate projected terrestrial drying over the Americas, and the mitigation benefit will emerge more quickly than with carbon capture. Innovative means of sulfur injection should continue to be explored as one potential low-cost climate solution.