Hi Franz, thanks very much for replies, good points.
My reason for drawing attention to the MacMartin article was that the Figure from it that I included is the best illustration I have seen of the vast superiority of solar geoengineering over carbon-based methods as a primary planetary cooling strategy. If others are aware of a better snapshot I would love to see it. The massive two degree cooling effect comes at a tiny fraction of the investment in emission reduction, illustrating how badly climate priorities are now skewed, and how the claim of locked-in warming is ignorant or a lie. I am not suggesting SAI is the best or only answer, just that the order of magnitude superiority of planetary brightening in general over carbon-based climate strategies as a rapid emergency response should be recognised and acknowledged and discussed, not ignored and distorted as now occurs in the broader public debate as seen at COP27. The main problem is a lack of political vision, advocacy and leadership. The questions you raise are very important, and can only be settled by an intensive international collaborative scientific research program with sound governance. I suspect the problems you describe with SAI might prove to be marginal, but that is something that needs careful study of evidence, looking at all the chemistry and all the effects of all proposals to increase albedo or remove system heat, whether by sea salt, iron, chlorine, sulphur, titanium or any other elements. A recent paper <https://www.tandfonline.com/doi/full/10.1080/14693062.2022.2091509> by David Keith and colleagues estimated that such a solar geoengineering research program could cost $2 billion, leading to savings of $10 trillion in avoided climate damage, a benefit 5000 times the research investment. My specific questions on your comments are if it may be possible that SAI would have a greater positive effect on preventing polar methane release, outweighing the negative methane effects you describe, and whether a tiny test dose of global SAI, say 0.1% of the 20 tg/y cited, or polar SAI at lower altitude, would help answer your questions. Best Regards Robert Tulip From: [email protected] <[email protected]> On Behalf Of Oeste Sent: Monday, 14 November 2022 2:22 PM To: Clive Elsworth <[email protected]>; David Henkel-Wallace <[email protected]>; Robert Tulip <[email protected]>; John Macdonald <[email protected]>; oswald.petersen <[email protected]>; Ernst Ries <[email protected]>; Maarten Van Herpen <[email protected]>; Dr Renaud de Richter <[email protected]>; Peter Fiekowsky <[email protected]> Cc: [email protected] Subject: Fwd: [geo] Synergistic and anti-synergistic scenarios for modeling solar radiation modification Hi Robert Since many years I kept in total opposition to SAI (Stratospheric Aerosol Injection) because to my opinion SAI would inhibit the methane depletion effect of ISA and its relatives EDARA and TOA and also the natural ISA effect from desert dust and also deplete the natural OH radical generation in the atmosphere. Meanwhile I must accept some additional aspects in the photochemical picture of the atmosphere which had been overseen by me and which might change the tropospheric chemistry model of SAI. This mind change concerns only to the SO2 Variant of SAI (additional all kind of sulfur containing gases which change by oxidation to sulfuric acid aerosol) but not those variants which use basic or neutral compounds just as carbonate or TiO2. It is known that the sea-salt aerosol particles within the boundary layer above the ocean become influenced by chemical compounds as DMS, COS and SO2 after their oxidation in the atmosphere to sulfuric acid aerosol which by coagulation with sea-salt particles produce gaseous HCl. This gaseous HCl is a precondition for the activation of all kind of aerosols like desert dust and aged HCl-depleted artificial aerosols containing iron just as ISA, also some TOA and EDARA variants. These aerosols are known to act by methane depletion, cloud whitening and/or cloud generation and also by phytoplankton nutrition which additional would trigger the cloud generation by DMS emission increase and also CO2 absorption by the ocean enhancement. Hence, if the SAI proponents might be able to demonstrate that the SO2 SAI variant is able to enhance the methane oxidation chemistry of desert dust and ISA above the ocean I would reduce my opposition against SAI. If the SAI proponents would be able to reduce the altitude of their aerosol emission from the stratosphere to the troposphere above the ocean I would be some more delighted. Independent from the altitude SO2 is emitted there must be certainty that SO2 will increase the methane depletion effect of ISA and relative aerosols. Our skepticism has also the reason that sulfate is known to have a inhibition effect on the chlorine atom generation by ferric chloride. Probably the effect disappears if the HCl partial pressure becomes increased above the usual 300 ppt HCl range in the atmosphere above the ocean but this fact has to be revealed. Franz -------- Weitergeleitete Nachricht -------- Betreff: Re: [geo] Scenarios for modeling solar radiation modification Datum: Sun, 13 Nov 2022 14:09:42 +0100 Von: Oeste <mailto:[email protected]> <[email protected]> An: [email protected] <mailto:[email protected]> Hi Robert All geoengineering options including SAI should presented not only with the focus on the only one physical, chemical or biochemical focus as done here by you: For instance, what happens exactly to the atmospheric chemistry and to the oceans biology if the mentioned SAI scenarios would happen. What would help the primary cooling if by a reduced atmospheric oxidant cleaning the life time of greenhouse gases decrease by SAI-reduced oxidation power? What would help the primary cooling if geoengineering options of greenhouse gas depletion become reduced or fail because of SAI-reduced sun radiation? As to compensate the increased greenhouse warming by such a SAI induced rise of methane and other greenhouse organics the needed TG-SO2 interventions/yr would need a further decrease. According to the direct oxygen consumption of the SO2 interventions also a massive decreasing influence of the oxydation power of the stratospheric chemistry would happen. This would increase also the life time of more or less oxidant resistant halogen methanes. An SAI induced reduction of daylight would decrease the vertical size of the photic zone. Also this might induce a lower phytoplankton productivity. Hence all this physical cooling possible by SAI can done by much more simple and cheeper cooling with cloud whitening and cloud generation, additional possibly also by MEER. Franz Am 13.11.2022 um 11:00 schrieb 'Robert Tulip' via geoengineering: This chart shows Stratospheric Aerosol Injection could deliver cooling of >2°C by 2070 compared to the optimistic IPCC projection of 4.5 w/m2 without SAI. That blows carbon-based cooling out of the water. Any time anyone says 1.5°C is passed, just show them this. Geoengineering is urgent. Source: D. G. MacMartin, D. Visioni , B. Kravitz, J.H. Richter, T. Felgenhauer, W. R. Lee, D. R. Morrow, E. A. Parson, and M. Sugiyama, Scenarios for modeling solar radiation modification, Proceedings of the National Academy of Science, August 2022 Fig. 3. High-level results from simulations involving different temperature targets: global mean temperature; SO2 injection rates; land average precipitation minus evaporation P-E; Arctic September sea-ice extent; total column ozone in southern hemisphere (SH), 60 to 90 ◦S in October (in Dobson Units, DU); Global Stratospheric Optical Depth; AMOC; and upper ocean heat content (indicative of thermosteric sea-level rise). From: [email protected] <mailto:[email protected]> <mailto:[email protected]> <[email protected]> On Behalf Of Andrew Lockley Sent: Wednesday, 9 November 2022 9:33 AM To: geoengineering <mailto:[email protected]> <[email protected]> Subject: [geo] Scenarios for modeling solar radiation modification Poster's note: not sure how this got missed. Authors D. G. MacMartin, D. Visioni B. Kravitz, and M. Sugiyama https://www.pnas.org/doi/full/10.1073/pnas.2202230119 Significance The benefits and risks of solar radiation modification (SRM; also known as solar geoengineering) need to be evaluated in context with the risks of climate change and will depend on choices such as the amount of cooling. One challenge today is a degree of arbitrariness in the scenarios used in current SRM simulations, making comparisons difficult both between SRM and non-SRM cases and between different SRM scenarios. We address this gap by 1) defining a set of plausible scenarios capturing a range of choices and uncertainties, and 2) providing simulations of these scenarios that can be broadly used for comparative impact assessment. This is an essential precursor to any international assessment by, e.g., the Intergovernmental Panel on Climate Change. Abstract Making informed future decisions about solar radiation modification (SRM; also known as solar geoengineering)—approaches such as stratospheric aerosol injection (SAI) that would cool the climate by reflecting sunlight—requires projections of the climate response and associated human and ecosystem impacts. These projections, in turn, will rely on simulations with global climate models. As with climate-change projections, these simulations need to adequately span a range of possible futures, describing different choices, such as start date and temperature target, as well as risks, such as termination or interruptions. SRM modeling simulations to date typically consider only a single scenario, often with some unrealistic or arbitrarily chosen elements (such as starting deployment in 2020), and have often been chosen based on scientific rather than policy-relevant considerations (e.g., choosing quite substantial cooling specifically to achieve a bigger response). This limits the ability to compare risks both between SRM and non-SRM scenarios and between different SRM scenarios. To address this gap, we begin by outlining some general considerations on scenario design for SRM. We then describe a specific set of scenarios to capture a range of possible policy choices and uncertainties and present corresponding SAI simulations intended for broad community use. Source: PNAS -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected] <mailto:[email protected]> . To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/CAJ3C-07rpTxFKKxyPVnOnhyrdqpDsD3284OTy-%2ByAB%2BASmHOOQ%40mail.gmail.com <https://groups.google.com/d/msgid/geoengineering/CAJ3C-07rpTxFKKxyPVnOnhyrdqpDsD3284OTy-%2ByAB%2BASmHOOQ%40mail.gmail.com?utm_medium=email&utm_source=footer> . -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected] <mailto:[email protected]> . To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/083901d8f746%24d2a80df0%2477f829d0%24%40yahoo.com.au <https://groups.google.com/d/msgid/geoengineering/083901d8f746%24d2a80df0%2477f829d0%24%40yahoo.com.au?utm_medium=email&utm_source=footer> . -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected] <mailto:[email protected]> . To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/9ba8f93f-d82f-e19f-898c-da7912aa0d9f%40gm-ingenieurbuero.com <https://groups.google.com/d/msgid/geoengineering/9ba8f93f-d82f-e19f-898c-da7912aa0d9f%40gm-ingenieurbuero.com?utm_medium=email&utm_source=footer> . -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/027701d8f7e2%247ff8f000%247fead000%24%40yahoo.com.au.
