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 <[email protected]> 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 >> Rutgers University E-mail: >> [email protected] >> 14 College Farm Road http://people.envsci.rutgers.edu/robock >> New Brunswick, NJ 08901-8551 ☮ https://twitter.com/AlanRobock >> >> >> >> >>> 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 >>>> Rutgers University E-mail: >>>> [email protected] >>>> 14 College Farm Road http://people.envsci.rutgers.edu/robock >>>> New Brunswick, NJ 08901-8551 ☮ https://twitter.com/AlanRobock >>>> >>>> >>>> >>>> >>>> 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 [email protected]. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/d/msgid/geoengineering/8d0d8c0a-0f0d-440c-9bb5-f8641560e4a0n%40googlegroups.com. >>>> >>> -- >>> 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/b541017e-b87b-4492-b840-91e39d0b0601n%40googlegroups.com. >> > > -- > 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/419bee77-0d9a-416a-9b38-5fc6f584ba3cn%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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