Hi all, I think I ought to clarify what I am trying to do and repose the question, as well as respond to all the replies. What I am attempting to do is this: Under low probability scenarios of nuclear war with high SRM burden (maybe due to a large warming, either because of high emissions or high ECS and TCR, either being far in excess of either the most likely scenarios or of the median values), would the termination "shock" have any effect? Not just would it be dwarfed by the effect of nuclear war, but would it truly be negligible in comparison? If not, what would the effect be? Why do I care about this; after all, a global nuclear war capable of producing civilizational collapse enough to cause SRM termination would kill billions, and as Mike MacKraken suggests, would massively change society (what I am terming "collapse")? - From many philosophical worldviews, it is important to know if such collapse would be permanent or lead to human extinction, or whether it is recoverable. These obviously exist on a spectrum, and thus whether something like SRM contributes to it being easier/harder for recovery from collapse is really important. - Whilst it is true that, in terms of the arguments you have been making, nuclear war is the real and most important problem, it is still important to know if large scale termination shock contributes in any meaningful way to either slightly increasing or slightly decreasing the damages from the nuclear winter. Such relatively small changes (a single order of magnitude lower lets say) may be important in terms of whether a collapse is recoverable (note the word may, I would be happy to hear evidence to the contrary)
Now onto responses to the points raised: In response to Alan and Gilles: In Alan's paper that Gilles cites, the temperature anomaly is less than 8K, and in Coupe et al 2019 which Alan cites on his website (as one of many excellent papers that he has co-authored), the temperature anomaly is of -10K. Of course, the impacts are not limited to cooling (nor the impacts of nuclear war limited to nuclear winter). Nonetheless, and please do tell me if I am missing something key here, it doesn't seem that the temperature anomaly that SRM termination would cause (be it +1K or +3K or others) would be entirely negligible. Of course, it would be dwarfed by the impact of nuclear war, which will cause the vast majority of the damage, causes the first catastrophe that causes civilizational collapse, and causes the deaths of billions. Nonetheless, I struggle to see how this by itself makes the impact of SRM induced forcing negligible. For instance, if, as Doug MacMartin is suggesting, SRM termination reduces the delta T from nuclear winter, even by 1K, surely that's somewhat significant. Please correct me if such an assessment is wrong. Similarly, if SRM makes the whole scenario worse, in the way that Seth Baum suggests in Baum (2013), then that is also significant. Even if it is small compared to the impact of nuclear winter, none of these plausible impacts seem negligible to me, even if we were only doing 1K of cooling with SRM (even less so if doing 3K of cooling). If I care about increasing the chance the civilizational collapse isn't permanent/ doesn't result in human extinction by any amount (be it 1 or 10%), then these questions seem significant. In response to Renaud and Andrew The catastrophe proposed in this scenario is a global catastrophe that essentially collapses civilisation, reducing the capacity of human organisation to such a degree that sustaining SRM would simply not be possible. This is the reason I somewhat doubt that a more local nuclear war could stop our capacity to carry out SRM, as I find the arguments in Parker and Irvine (2018) with regards to the requirements for termination shock to be robust and compelling, hence the scenario I have set out. In response to a lot of the general vibe of the conversation: Of course nuclear war is the main thing to worry about; it is the dominant major catastrophe. However, what I am trying to do is a risk-risk analysis of what Tang and Kemp (2021) [https://www.frontiersin.org/articles/10.3389/fclim.2021.720312/full#:~:text=Stratospheric%20Aerosol%20Injection%20and%20Global%20Catastrophic%20Risk,-Aaron%20Tang1&text=Injecting%20particles%20into%20atmosphere%20to,the%20threat%20of%20climate%20change.] describe as latent risk of SRM; key global catastrophic risks that are only activiated given certain scenarios. In particular, I am trying to test the robustness of the concept of "double catastrophe" of SRM being significantly worse than the "single catastrophe" given the same warming but no SRM, which is introduced in Baum et al 2013 [https://gcrinstitute.org/papers/003_double-catastrophe.pdf] without much supporting evidence. I am sceptical that a nuclear war + SRM is worse than a nuclear war with no SRM; in fact, if anything, the former seems on first assumptions to be slightly better. However, given the importance of such a question (if it occurred it may lead to an increased probability of human extinction) and the neglectedness of such low probability high impact risks, it seems to me wrong to reject the question out of hand. In the field of Global Catastrophic Risk studies, we are dealing with low probability high impact events. I am not saying that this scenario will happen, or is even likely to happen. But we plug ourselves in when we go in our car, despite a car crash on any given journey being unlikely, because the consequences are so severe. So what I want to try and work out is if there is any valid concerns here, even if we think those concerns only have a <10% or even <5% probability of occurring. I hope I have better clarified what I am trying to ask, and I do apologise for any confusion. I am really thankful for your responses so far, and apologies if I have misinterpreted what you have been saying thus far. I am happy to answer any concerns, and please do say if you think I am simply speaking nonsense Kind Regards Gideon Futerman On Wednesday, 27 July 2022 at 06:58:31 UTC+1 gdebr...@gmail.com wrote: > FYI Updated nuclear winter analysis is so much worse than SAI that it's > pointless to consider. > > *Nuclear winter revisited with a modern climate model and current nuclear > arsenals: Still catastrophic consequences* > Alan Robock,1 Luke Oman,1,2 and Georgiy L. Stenchikov1 > Received 8 November 2006; revised 2 April 2007; accepted 27 April 2007; > published 6 July 2007 > https://climate.envsci.rutgers.edu/pdf/RobockNW2006JD008235.pdf > > Gilles de Brouwer > > > On Tue, Jul 26, 2022 at 5:50 PM Gideon Futerman <ggfut...@gmail.com> > wrote: > >> Apologies, you are correct, I was using the ECS values from AR5 and >> forgot it had reduced with AR6. I was also getting my range vs values mixed >> up. >> Nonetheless, a similar point still broadly stands- the ipcc suggests with >> only medium confidence that it is "very likely" that ECS is between 2K and >> 5K (not 6K as I had previously stated), putting a warming of anything above >> 5K therefore at between 0-5% probability with medium confidence. >> Whilst I appreciate the desire to focus on the median ECS, I think it is >> nonetheless important to consider the more extreme, fat tailed risks. Not >> because these will happen or are likely to happen, but because in general >> such worse case scenario, low probability high impact scenarios are >> neglected. >> This is the same reason I care about SRM in concert with a nuclear war. >> Not because I want to overplay how important SRM is under such a scenario, >> but merely want to explore the worse case scenarios. I don’t think >> (certainly hope not) that any of the scenarios the RESILIENCER Project >> explores are likely, certainly none are the median scenarios. Rather, they >> are those scenarios in the fat tails of the possible risks. >> I understand why there is aversion to me exploring such risks; I would >> hate people to think that I am claiming the research community at large >> should start focusing on such risks (which would be foolish). Nonetheless, >> it seems odd to not at least some degree look at these more extreme, much >> less likely, scenarios. >> >> On Tue, 26 Jul 2022, 22:33 Daniele Visioni, <daniele...@gmail.com> wrote: >> >>> Dear Gideon, >>> not to pile on but I feel like this should be corrected: none of the >>> most current IPCC projections say that 550ppm have a 10% chance of leaving >>> us with 6K of warming. >>> Even the most high sensitivity models in CMIP6 only show a ECS of, at >>> most, 5 per doubling of CO₂ (so 560), but the best estimate is still around >>> 3K given a whole range of approaches to estimate it. >>> For more relevant IPCC scenarios during this century, given transient >>> sensitivity and more, scenarios that lead to 550ppm (considering also other >>> GHG, LUC, aerosols) like SSP2-4.5 have a median warming of a bit less than >>> 3K. >>> How can surely say the IPCC is wrong and climate models are wrong, of >>> course. >>> >>> (Ça vas sans dire, I’m not trying to downplay climate change! But being >>> precise helps having better discussions :) ) >>> >>> >>> On 26 Jul 2022, at 17:20, Gideon Futerman <ggfut...@gmail.com> wrote: >>> >>> Dear Dr Robock, >>> Whilst I would admit that 3K of cooling by SRM is unlikely, it is >>> certainly not out of the range of possibility. Given CO2 concentrations of >>> 550PPM have a 10% chance of leaving us with 6K of warming (and that >>> certainly doesn't seem to be an unreasonable amount of emissions given >>> mitigation trajectories), it certainly doesn't seem like there is a less >>> than 10% probability of a given deployment scheme being 3K of forcing. >>> Secondly, why care about this if there is a nuclear war. Maybe you are >>> correct, and there is no worry. But if you care about post-nuclear war >>> societal recovery, it may be important to know whether SRM-driven >>> termination shock makes that more or less likely, or is entirely >>> negligible. Of course, the primary worry here is avoid the initial >>> catastrophe (nuclear war). Nonetheless, the question of whether SRM >>> termination shock under nuclear war has any effect (even if only 10% of the >>> magnitude of the effects of the nuclear war) is significant. >>> I am trying to look at low probability, heavy tailed risks of SRM, >>> including how it interacts with other risks. This is why I want to look at >>> the (relatively unlikely) scenario which I have laid out. >>> And apologies for the spelling mistake, spelling is certainly not my >>> strong suit! >>> Kind Regards >>> Gideon Futerman >>> He/Him >>> www.resiliencer.org >>> On Tuesday, 26 July 2022 at 16:05:48 UTC+1 Alan Robock wrote: >>> >>>> Dear Gideon, >>>> >>>> It is spelled "negligible." And nobody is suggesting enough SAI to >>>> produce 3K cooling, because that means there has been no mitigation. >>>> >>>> A nuclear war could kill billions of people from starvation, and would >>>> collapse civilization, surely reducing greenhouse gas emissions. Why >>>> would >>>> you even worry about global warming and geoengineering then? That's why I >>>> say your are comparing two things that are of completely different scales. >>>> >>>> >>>> Alan Robock >>>> >>>> Alan Robock, Distinguished Professor >>>> Department of Environmental Sciences Phone: +1-848-932-5751 >>>> <(848)%20932-5751> >>>> Rutgers University E-mail: >>>> rob...@envsci.rutgers.edu >>>> 14 College Farm Road http://people.envsci.rutgers.edu/robock >>>> New Brunswick, NJ 08901-8551 ☮ https://twitter.com/AlanRobock >>>> >>>> [image: Signature] >>>> >>>> >>>> On 7/26/2022 10:59 AM, Gideon Futerman wrote: >>>> >>>> Dear Alan Robock, >>>> When you say overwhelm, is the suggestion here that the increase in >>>> radiative forcing from the termination of aerosol injection would be >>>> entirely negligable compared to the nuclear winter scenario? >>>> If SAI were masking 3K of warming, and you got a nuclear winter driven >>>> cooling of say 7K, surely the impact of the termination of SAI would not >>>> be >>>> negligable, even if it would be significantly less than the cooling of >>>> nuclear winter (ie you still get a nuclear winter)? I am trying to work >>>> out >>>> if the "double catastrophe" as Baum calls it actually applies in the >>>> nuclear winter scenario. So the question of whether the removal of the >>>> contribution of SAI to radiative forcing (by termination) makes the >>>> nuclear >>>> winter (and the resulting warming afterwards) worse, less bad or is >>>> entirely negligable is important. >>>> Moreover might sunlight removal effects be important in the short term, >>>> particularly if it were a relatively high SAI radiative forcing and >>>> (relatively) minor nuclear winter (say about 6K of cooling)? Given up to >>>> 50% of sulfate aerosols remain in the stratosphere up to 8 months after >>>> termination, would the added impact of the sulfate aerosols on top of the >>>> significantly more soot aerosols have an effect of sunlight available for >>>> photosynthesis, so increase impact on food production in the early days of >>>> the nuclear winter? Or would this simply be negligable in the face of the >>>> radiation reduction from even a relatively minor nuclear winter? >>>> Kind Regards >>>> Gideon >>>> >>>> >>>> On Tuesday, 26 July 2022 at 15:20:44 UTC+1 Alan Robock wrote: >>>> >>>>> Dear Gideon, >>>>> >>>>> A nuclear war would be orders of magnitude worse than any impacts of >>>>> SAI or termination. Soot from fires ignited by nuclear attacks on cities >>>>> and industrial areas would last for many years, and would overwhelm any >>>>> impacts from shorter lived sulfate aerosols. Of course the impacts >>>>> depend >>>>> on how much soot, but a war between the US and Russia could produce a >>>>> nuclear winter. For more information on our work and the consequences >>>>> of >>>>> nuclear war, please visit http://climate.envsci.rutgers.edu/nuclear/ >>>>> >>>>> Alan Robock >>>>> >>>>> Alan Robock, Distinguished Professor >>>>> Department of Environmental Sciences Phone: +1-848-932-5751 >>>>> <(848)%20932-5751> >>>>> Rutgers University E-mail: >>>>> rob...@envsci.rutgers.edu >>>>> 14 College Farm Road >>>>> http://people.envsci.rutgers.edu/robock >>>>> New Brunswick, NJ 08901-8551 ☮ https://twitter.com/AlanRobock >>>>> >>>>> [image: Signature] >>>>> >>>>> >>>>> On 7/26/2022 10:03 AM, Gideon Futerman wrote: >>>>> >>>>> As part of the RESILIENCER Project, we are looking at low probability >>>>> high impact events and their relation to SRM. One important worry in this >>>>> regards becomes termination shock, most importantly what Baum (2013) >>>>> calls >>>>> a "Double Catastrophe" where a global societal collapse caused by one >>>>> catastrophe then causes termination shock, another catastrophe, which may >>>>> convert the civilisational collapse into a risk of extinction. >>>>> >>>>> One such initial catastrophe may be nuclear war. Thus, the combination >>>>> of SRM and nuclear war may be a significant worry. As such, I am posing >>>>> the >>>>> question to the google group: what would happen if SRM (either >>>>> stratospheric or tropospheric- or space based if you want to go there) >>>>> was >>>>> terminated due to a nuclear war? What sort of effects would you expect to >>>>> see? Would the combination worsen the effects of nuclear war or help >>>>> ameliorate them? How would this differ between SRM types? >>>>> >>>>> >>>>> -- >>>>> 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 geoengineerin...@googlegroups.com. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/d/msgid/geoengineering/8d0d8c0a-0f0d-440c-9bb5-f8641560e4a0n%40googlegroups.com >>>>> >>>>> <https://groups.google.com/d/msgid/geoengineering/8d0d8c0a-0f0d-440c-9bb5-f8641560e4a0n%40googlegroups.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 geoengineerin...@googlegroups.com. >>>> >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/geoengineering/b541017e-b87b-4492-b840-91e39d0b0601n%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/geoengineering/b541017e-b87b-4492-b840-91e39d0b0601n%40googlegroups.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 geoengineerin...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/geoengineering/419bee77-0d9a-416a-9b38-5fc6f584ba3cn%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/geoengineering/419bee77-0d9a-416a-9b38-5fc6f584ba3cn%40googlegroups.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 geoengineerin...@googlegroups.com. >> > To view this discussion on the web visit >> https://groups.google.com/d/msgid/geoengineering/CAK73TM%2BA0dvOcYEOQd1_CKFE6YM1KZjTSQUo2HvZqhvRY4HMUw%40mail.gmail.com >> >> <https://groups.google.com/d/msgid/geoengineering/CAK73TM%2BA0dvOcYEOQd1_CKFE6YM1KZjTSQUo2HvZqhvRY4HMUw%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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