Scenarios for modeling solar radiation modification
Andrew Lockley
Robert Tulip
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).
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Oeste
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
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Oeste
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
| Betreff: | Re: [geo] Scenarios for modeling solar radiation modification |
|---|---|
| Datum: | Sun, 13 Nov 2022 14:09:42 +0100 |
| Von: | Oeste <oe...@gm-ingenieurbuero.com> |
| An: | geoengi...@googlegroups.com |
Robert Tulip
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 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
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Andrew Lockley
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Oeste
Hi Andrew
Many thanks for this interesting paper which I am going to study. Surely I will give my comment about in the next days.
Best
Franz Oeste
Douglas MacMartin
Also worth keeping in mind the context that ~1C of cooling (i.e., quite a lot) requires an amount of SO2 that is roughly 10% of current anthropogenic SO2 emissions, though not with the same geographic distribution nor the same size distribution of sulfate aerosols when it ultimately comes down into the troposphere, however briefly.
Broadly I agree that of course we need more research to understand effects.
But there aren’t *any* options on the table at this point that don’t come with downsides, so rather than being opposed to one particular choice because there exists a downside, the right approach is ultimately to weigh the benefits and harms of different choices that could be made about the future.
(And the statement about “could be done much more simply and cheaper” by cloud whitening isn’t supportable, I don’t think anyone knows whether either of those claims are true or not true… and of course MCB *also* has downsides, so neither simplicity nor cost are really the relevant criteria one should be using to pick.)
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Stephen Salter
Doug
You write that claims for marine cloud brightening are not supportable.
Sean Twomey’s work used aircraft observation from real clouds. It has been replicated by Andrew Ackerman. The optics can be demonstrated with jars of glass balls. Ship tracks can sometimes show reflectivity changes an order of magnitude greater than would be needed for complete cancelation of the present thermal problem.
I agree that there are some conditions where rain can be triggered to clear clouds and so produce warming but if we know what these conditions are we can avoid them.
People lose their jobs if they reveal the true cost of making a product. We have to use figures from historical production of items of similar power, weight, complexity and operating environment. Most ships are made in small numbers. A exception was the Flower class corvettes built in 1940. They displaced 925 tonnes rather than 90 for a spray vessel. The power rating was 2 MW rather than 300 kW. They cost £60,000 when the annual salary for a top PhD graduate was £600 and sailors were paid £0.1 per day.
For more up-to-date estimates you might have noticed that the flapping hydrofoil mechanism we want to use for power generation in a spray vessel bears a striking resemblance to the mechanism of earth-moving machinery. Today the cost of big diggers is £9000 per tonne. They are fitted with satellite navigation and air conditioning. Until we can get firm quotations we can use this plus index linking to estimate that, in mass production, spay vessels will cost $4 million each. If we us the Twomey equations explained by Schwartz and Slingo in the graph below we can see how many would be needed.
Allowing for vessels in the wrong place and out of action we might need 1000 of them. If the life is 25 years the annual cost of maintenance and interest payments of fleet ownership would be about 10% of initial capital would be $400 million. If you estimate costs of sea level rise, hurricanes and climate refugees you will see that this is very close to zero.
You can estimate side effects of marine cloud brightening from work by Stjern et al. at the Norwegian Cicero labs following an increase of 50% in the concentration of cloud condensation nuclei in ocean regions with low cloud. These are shown below. The extra cooling round the north would be very welcome. Precipitation increases, green/blue, are in drought-stricken regions. The brown reductions are over the sea. We could provide desalination for small islands.
This is far more intelligent that spraying all year round between latitudes 30 N and 30 S but I am sure that we could learn to do even better with real-time satellite observations driving ‘what if?’ quantum computer climate models. It takes only one mouse click and the time to the next rain shower to change the plan. This is far more intelligent that spraying all year round between latitudes 30 N and 30 S but I am sure that we could learn to do even better with real-time satellite observations driving ‘what if?’ quantum computer climate models. It takes only one mouse click and the time to the next rain shower to change the plan.
Stephen
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Subject: RE: [geo] Synergistic and anti-synergistic scenarios for modeling solar radiation modification
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Douglas MacMartin
Stephen,
I did not write anything implying that *all* claims about MCB are unsupportable, what I wrote was that “the statement about “could be done much more simply and cheaper” by cloud whitening isn’t supportable”. So most of your email is rather tangential. And, since neither simplicity nor cost are really relevant factors in deciding anything, this whole thing is just a tangent.
Simplicity, of course, is hard to judge; SAI requires a supply chain and aircraft, MCB requires nozzles and ships and some way of determining where/when to spray… is that simpler? Probably depends on how carefully one has to manage when/where to spray, which we don’t really know, so I don’t think one can claim that one approach is simpler than the other. And as long as both MCB and SAI are reasonably doable, I actually don’t care which is simpler.
And when we don’t know much about details of when and where to spray (as you acknowledge) and how carefully one needs to adjust one’s spraying, it’s a bit difficult to come up with a truly credible cost estimate for MCB; your very rough numbers below are the most refined engineering estimates anyone has ever come up with, and no offense, but I don’t think that alone should be used as a basis for costing decisions… once we know more about the physics it would be great to get better cost numbers. Again, I don’t actually know why someone would write cost as a metric in the first place, because I think both are so cheap that it’s not a significant factor in decisions. But I don’t think we know enough to emphatically claim that one approach is cheaper than the other.
As for side effects, yes, there are climatic ones, which we don’t know well (even current models have pretty high uncertainty in representing the effects of adding aerosols to clouds, so no-one should put much faith in the details of precip plots yet), and there are of course other effects too including ocean bio that was mentioned below (though solely in context of SAI, of course it’s also relevant for MCB).
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