I've just tried running some really simple equations to look at forcing, so I thought I would share my back of the envelope calculations and see what you all think. So I tried to calculate what would happen to forcing in a 5Tg of soot released (likely due to a regional nuclear war) combined with a termination shock, possibly due to cascading impacts of the nuclear war on the global economy, for example. I used a value of -15Wm^-2 for the maximum forcing from the soot, and a e-folding time of 4.6 years [Robock et al 2007]. I then used a solar geoengineering forcing of -4Wm^-2 (the maximum forcing from Pinatubo) and an e-folding time of 1 year. I treated the forcing relative to the nongeoengineered world prior to the nuclear winter, so treated that as 0Wm^-2 and the forcing of the geoengineered world before the nuclear winter at 4Wm^-2. The soot was injected at the end of year 1. Immediately after soot injection at the end of year 1, the forcing(geo) is -19Wm^-2 and the forcing(nongeo) is -15Wm^-2. At the end of year 2, so 1 year after the soot injection, the forcing (geo) is 14Wm^-2 and the forcing(nongeo) is 12Wm^-2, so the delta for the forcing(geo) relative to their initial values is 16.7% less than the delta forcing (nongeo). The two equations I used for year 1 were as follows: y=0 (nongeo) y=-4 (geo) The two equations I used for the end of year 1 onwards were y=-15e ^(-1/4.6 * (t-1)) [nongeo] y=-15e^(-1/4.6 * (t-1)) -3e^(-(t-1)) [geo]
The graph I got is here (https://www.desmos.com/calculator/duz3tlpkky) It seems to me for a relatively small scale nuclear winter and a moderately large SRM forcing that the forcing impacts of termination shock are not negligable. This obviously doesn't necessarily translate to climate respone I did a few others for other SRM and nuclear war scenarios, which I can send through if people were interested. Obviously these calculations are massively simplified, back of the envelope calculations, but I would nonetheless be interested in peoples thoughts on it. Apologies if I have messed up somewhere Kind Regards Gideon On Sunday, 7 August 2022 at 01:36:17 UTC+1 Russell Seitz wrote: > I'm surprised Alan should neglect to cite studies other than his own, as > climate responses to carbon aerosols in the atmosphere vary greatly. The > recent literature is illustrative- a growing concern is the impact of > black carbon from satellite and spacecraft launches, which may warm the > upper atmosphere rather than cool it: > > Journal of Geophysical Research: Atmospheres > <https://agupubs.onlinelibrary.wiley.com/journal/21698996> 1June2022 > > The Climate and Ozone Impacts of Black Carbon Emissions From Global Rocket > Launches > Christopher M Maloney > <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorRaw=Maloney%2C+Christopher+M> > , Robert W Portmann > <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorRaw=Portmann%2C+Robert+W> > , Martin N Ross > <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorRaw=Ross%2C+Martin+N> > , Karen H Rosenlof > <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorRaw=Rosenlof%2C+Karen+H> > > https://doi.org/10.1029/2021JD036373 > > Aerosol emissions from spaceflight activities play a small but increasing > role in the background stratospheric aerosol population. Rockets used by > the global launch industry emit black carbon (BC) particles directly into > the stratosphere where they accumulate, absorb solar radiation, and warm > the surrounding air. We model the chemical and dynamical response of the > atmosphere to northern mid-latitude rocket BC emissions. We initially > examine emissions at a rate of 10 Gg per year, which is an order of > magnitude larger than current emissions, but consistent with extrapolations > of space traffic growth several decades into the future. We also perform > runs at 30 and 100 Gg per year in order to better delineate the > atmosphere's response to rocket BC emissions. We show that a 10 Gg/yr > rocket BC emission increases stratospheric temperatures by as much as 1.5 K > in the stratosphere. Changes in global circulation also occur. For example, > the annual subtropical jet wind speeds slow down by as much as 5 m/s, while > a 10%–20% weakening of the overturning circulation occurs in the northern > hemisphere during multiple seasons. Warming temperatures lead to a ozone > reduction in the northern hemisphere by as much as 16 DU in some months. > The climate response increases in a near linear fashion when looking at > larger 30 and 100 Gg emission scenarios. Comparing the amplitude of the > atmospheric response using different emission rates provides insight into > stratospheric adjustment and feedback mechanisms. Our results show that the > stratosphere is sensitive to relatively modest BC injections. > > On Tuesday, July 26, 2022 at 10:20:44 AM UTC-4 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: >> [email protected] >> 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? 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