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https://doi.org/10.5194/egusphere-2023-1753
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2023-1753
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
10 Oct 2023
| 10 Oct 2023
Status: this preprint is open for discussion.
The interaction of Solar Radiation Modification and Earth System Tipping Elements
Gideon Futerman
CORRESPONDING AUTHOR
Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, United Kingdom
Mira Adhikari
Department of Geography, Kings College London, London, WC2B 4BG, United Kingdom
Alistair Duffey
Department of Earth Sciences, University College London, WC1E 6BT, United Kingdom
Yuanchao Fan
Tsinghua Shenzhen International Graduate School, China
Peter Irvine
Department of Earth Sciences, University College London, WC1E 6BT, United Kingdom
Jessica Gurevitch
Department of Ecology and Evolution, Stony Brook University, NY 11794‐5245, United States of America
Claudia Wieners
Institute for Marine and Atmospheric Research, Utrecht University, 3584 CC, Netherlands
Abstract. The avoidance of hitting tipping points is often considered a key benefit of Solar Radiation Modification (SRM) techniques, however, the physical science underpinning this has thus far not been comprehensively assessed. This review assesses the available evidence for the interaction of SRM with a number of earth system tipping elements in the cryosphere, the oceans, the atmosphere and the biosphere , with a particular focus on the impact of SAI. We review the scant available literature directly addressing the interaction of SRM with the tipping elements or for closely related proxies to these elements. However, given how limited this evidence is, we also identify and describe the drivers of the tipping elements, and then assess the available evidence for the impact of SRM on these. We then briefly assess whether SRM could halt or reverse tipping once feedbacks have been initiated. Finally, we suggest pathways for further research. We find that SRM mostly reduces the risk of hitting tipping points relative to same emission pathway scenarios without SRM, although this conclusion is not clear for every tipping element, and large uncertainties remain.
How to cite. Futerman, G., Adhikari, M., Duffey, A., Fan, Y., Irvine, P., Gurevitch, J., and Wieners, C.: The interaction of Solar Radiation Modification and Earth System Tipping Elements, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1753, 2023.
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Gideon Futerman et al.
Status: open (until 14 Dec 2023)
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
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RC1: 'Comment on egusphere-2023-1753', Anonymous Referee #1, 26 Nov 2023
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The paper “The interaction of solar radiation modification with Earth System Tipping Elements” by Futerman et al., explores the current state of the literature of the effects of solar radiation modification (SRM) on climate tipping elements. This is a very timely review that should indeed be carried out in order to inform future research on SRM; therefore, I believe that the authors have a very good reasoning for their review article at this critical point in time. While I can see the time and effort that the authors put in this review article, I found the rationale of the article difficult to grasp and think that several changes are necessary before this article can be considered for publication in Earth System Dynamics. I apologize for my critical feedback and I hope the authors will find the comments below helpful for their decision on how to proceed.
Key points:
- Streamlining of the article: Throughout the article, each of the tipping elements is split up into four parts: (i) Current state of the tipping element; (ii) Drivers and Feedbacks; (iii) Impacts of SRM; (iv) Further research. While I think that the core of the paper is in (iii), I do not think that another review on the current state of the tipping elements as well as drivers and feedbacks is necessary (not the main topic of this paper, is it?) or helpful (the current state of the tipping elements is done in the global tipping points report and the many other papers of this special issue). Therefore, I suggest to strongly cut those parts (maybe put the long version in an SI if the authors would like to keep this information). For instance, the section on Mountain Glaciers (2.3) had a good balance between the subsections in my view.
This is not to say that I didn’t find this information valuable and interesting to read, but it distracts from the main purpose of this article (SRM) in my view. - Rationale of the article: The above (my point 1) is partially reflected in the abstract where the authors state that they review the literature on SRM but given that there is not a lot of literature they state that additionally a review of the current state of tipping elements as well as their drivers and feedbacks was carried out. I think this rationale is invalid and needs to be sharpened. In my view, a review on SRM on tipping elements is warranted even if the current state of literature is still immature and sparse in some places. This should be reflected in the abstract and the text overall. It can, however, not be an excuse to add only partially related parts to a paper because literature evidence of a certain aspect is weak.
- Main results/Table 1: I think this is the main outcome of the paper and I like it very much (with some smaller suggestions below). This table should be placed in the beginning and then elaborated in the specific sections. This gives the reader a clear picture of the main results early on in the article instead of after 47 pages of text – I believe this table is also not announced before so that the reader could anticipate. I also strongly recommend to add at least one further figure that graphically represents the table, e.g. on a world map populated with the tipping elements and their reaction to SRM.
Overall, I believe that the manuscript would profit a lot from a clearer focus on SRM. Some concrete points below.
Major points:
- I find that section 1.3 (Solar Radiation Modification and Tipping Elements) could be streamlined strongly.
- While figure 1 is illustrative, I am unsure whether this is really useful in this manuscript because it is not a result from this paper but a reproduction.
- In my view, this is similar for figure 2 as long as there are no studies that discuss how SRM directly alters Atlantic Ocean circulations; if there are, please add them to the figure.
- Figure 3 is a general figure of S-shapes that allows for different types of tipping (forcing, noise, rate, …). As such, this figure is not specific to the AMOC and should either be removed or moved up to the introduction. It may actually be a good figure to discuss threshold-free feedbacks as opposed to different types of tipping in the introduction.
- Page 12, l 322-346: Can be strongly shortened in my opinion. In particular if there are not many studies that discuss SRM, then this should be stated, and additional CDR studies (e.g. Garbe et al., 2020) should be kept very brief as this is not the main contribution of the paper as I understand.
- Pages 32-35: The impact of SRM on ecological systems in general: As opposed to the other sections which are excellently referenced, this section is not. Further, my overall feeling is that this section can be condensed to around 20-35% of text lengths.
- Section 5.2: Dipterocarp Forests: This is not a global tipping element. Why is it discussed in this manuscript? Do the authors suggest that it should be considered a climate tipping element because it is relevant on the global scale? For me, it sounds regionally very relevant but more like a super-regional regime shift rather than a global tipping element (e.g. see Rocha et al., 2018, Science: 1126/science.aat7850). Maybe this section can be moved to the SI or removed.
- Section 5.5: Indian subcontinent biodiversity hotspots: It is unclear to me why this section is included because (i) it is not a climate tipping element and (ii) there are also hotspots of biodiversity in Africa, Indonesia and particular in South America. Therefore, I suggest to move this section in the SI of the paper or remove it.
- Comments to Table 1, which is really helpful:
- Column: Overall confidence of what is meant here? Overall confidence of SRM being able to reverse tipping? Overall confidence (=agreement) of the literature on column “Can SAI reverse tipping”
- Rows “Dipterocarp Forest” and “Indian Subcontinent Biodiversity Hotspots”: How can SRM help once tipping is completed (as noted in “b. Likely” in column 4). Once biodiversity is lost or a forest has died back, SRM cannot help to restore these systems as they have developed and adapted over millions of years.
- Section 6.1 (Further Research): I suggest to keep these sections short because for each of the tipping elements, it is already discussed where future research can broaden knowledge.
There is a number of smaller points - Minor points:
- Abstract: Please write SAI in the abstract out at first occurrence
- Page 2, line 45: Also cite Levermann et al., 2012: https://doi.org/10.1007/s10584-011-0126-5
On page 846 is a definition of tipping elements - Page 2, line 53-56: The definition of ecological tipping elements is unclear. In Armstrong McKay, tipping of ecosystems means a large-scale state shift of the Amazon rainforest, boreal forests, or coral reefs. The death of single species does not constitute a tipping in the Earth system sense. Please clarify.
- Page 2, l 59: Can you directly here give an example of a threshold-free feedback? (maybe this is a good spot for figure 3)
- Page 3, l 79: “… has been exceeded for sufficiently long times” What you mean are so-called overshoots. Replace citations by
- Ritchie et al., 2021: https://doi.org/10.1038/s41586-021-03263-2
- Wunderling et al., 2023: https://doi.org/10.1038/s41558-022-01545-9
- Page 4, l 99: Irvine et al., 2019 does not exist in the reference list but only Irvine et al., 2018. Please check.
- Page 7, l 184, cite Levermann, Winkelmann, 2016, The Cryosphere: https://doi.org/10.5194/tc-10-1799-2016
- Page 13, l 369: Did the authors really mean 2089, not 2099?
- Page 26/27: Formatting changes twice, please check.
- Page 31, l 894: The Schneider et al., 2019 paper on a 10°C warming due to cloud changes is speculative (given its huge temperature feedback). This should be stated somewhere around these lines.
- Page 37, chapter 5.3. Amazon basin: In the introductory paragraph, the combined adverse influence of deforestation, human-made fires, and climate change on the Amazon rainforest could be discussed more directly.
- Somewhere in this section, the new Bochow et al., 2023, Science Advances paper should be cited: 1126/sciadv.add9973
- I believe MCB (probably Marine Cloud Brightening) is only used as an abbreviation
- Page 46: I think this study by Rao et al., 2023 in Communications Earth and Environment should be discussed briefly in this section (https://doi.org/10.1038/s43247-023-00910-6)
Citation: https://doi.org/10.5194/egusphere-2023-1753-RC1 - Streamlining of the article: Throughout the article, each of the tipping elements is split up into four parts: (i) Current state of the tipping element; (ii) Drivers and Feedbacks; (iii) Impacts of SRM; (iv) Further research. While I think that the core of the paper is in (iii), I do not think that another review on the current state of the tipping elements as well as drivers and feedbacks is necessary (not the main topic of this paper, is it?) or helpful (the current state of the tipping elements is done in the global tipping points report and the many other papers of this special issue). Therefore, I suggest to strongly cut those parts (maybe put the long version in an SI if the authors would like to keep this information). For instance, the section on Mountain Glaciers (2.3) had a good balance between the subsections in my view.
Gideon Futerman et al.
Gideon Futerman et al.
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Short summary
This review assesses the interaction of Solar Radiation Modification (SRM), a technology to reduce the impacts of climate change by reflecting sunlight, and earth system tipping points. We find that SRM reduces the risk of hitting most of the tipping points that we studied relative to the same emission pathway although for some systems this is more complex. Uncertainties for almost all tipping elements studied were high, so we also lay out suggestions for future research.
This review assesses the interaction of Solar Radiation Modification (SRM), a technology to...