Nuclear Winter and SRM (including termination shock)

[Gideon Futerman]

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?

[Alan Robock ☮]

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: rob...@envsci.rutgers.edu
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?

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[Gideon Futerman]

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

[Alan Robock ☮]

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: rob...@envsci.rutgers.edu
14 College Farm Road            http://people.envsci.rutgers.edu/robock
New Brunswick, NJ 08901-8551     ☮ https://twitter.com/AlanRobock

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[Gideon Futerman]

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

[Michael MacCracken]

I'm with Alan on this one.

With 3 C warming offset by SAI, if done thoughtfully the society and agriculture  would have been adjusting along the way, and then comes nuclear war to disturb that ongoing situation.

And as the SCOPE study on the consequences of nuclear war made clear, there is the matter of the direct damage. As that report noted it would take destruction of only a few of the world's financial centers to collapse international trade of medicines, seeds, fertilizers, grain and much more (computer chips, coffee). As we are seeing from the invasion of Ukraine, which is one of the top exporters of grains and fertilizer, disrupting this producing area has prospects for causing widespread starvation. For each of the major grains in international trade, something like 90% comes from typically five countries or so, with their exports going to of order 100 countries importing the grain in order to provide reasonably priced food for their people. And then add sudden disruption of the weather in these key zones and making it difficult for nations around the world, global nuclear war would be overwhelmingly worse.

What would happen to the conditions of the following years might be of theoretical interest, but the consequences of the first months and year would have created such disruption that the society you'd be considering would be almost unimaginably different.

Mike MacCracken

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[Stephen Salter]

Hi All

About nuclear winters. I think that the post war effects of nuclear war with marine cloud brightening in the troposphere will differ from those of stratospheric sulphur. 

My understanding is that a large nuclear exchange will produce lots of dust and smoke and so a long period of reduced solar input, more that we might have chosen for global heating.  This will initially be concentrated over land.  Aerosol in the stratosphere from geoengineering will add to the cooling effect of nuclear weapons, perhaps for a year or more.

But aerosol from marine cloud brightening will initially be over the ocean and will be washed out by the next rain or snow shower and so will add less to the cooling.

We could argue that droughts caused by climate change are likely triggers of conflicts, some of which could lead to nuclear war.  Anything which reduces the possibility of drought, such as the result from Stjern et al. below (from doi.org/10.5194/acp-18-621-2018-supplement), should be actively encouraged by everyone worried by post nuclear effects. This was the mean of nine leading climate models following an increase of cloud condensation nuclei by only 50% in ocean regions of low cloud. I am sure that intelligent climate engineers with satellite data feeding quantum computers running “what if ”  climate models do even better, especially if they were Norwegian.

 

 

Let us hope that the probability of nuclear war is too low to affect decisions about climate control.  But large volcanic eruptions are certain and the probability of one in the lifetime of people alive today could easily approach unity.

 

Alan Robock writes that nobody is suggesting enough stratospheric aerosol to produce 3 K of cooling.  I want to suggest that marine cloud brightening might very well be needed to do this amount of cooling in selected regions to save ice, moderate hurricanes or remove an unwanted hot blob.  The Twomey equations as explained by Schwarz and Slingo show that this would be quite possible.  The 50% increase of the Stjern work gave 4 K over the Arctic. The change in aerosol concentration needed for this are given in the diagram below.

 

Before the Reagan-Gorbachev agreement I worked on an idea which gave a mathematical certainty that two jealous rival superpowers would BOTH believe that they had screwed each other as they gave up their nuclear weapons. Perceptions of comfort and threat of different weapon systems are not the same.  Both sides would write a list of all their nuclear inventory with a percentage number for their view of the comfort value of each weapon. Side A would agree to give up any small fraction of their inventory chosen by Side B if the Side B gave up the same small fraction which seemed most threatening in the view of Side A. The Pershing missile could reach Moscow from Germany in 8 minutes looks much more dangerous than something launched from a submarine. After each round each side could adjust their numbers and then select their next choices. The logic is the same as discussions about jealous children sharing a cake with an uneven mix of cherries and icing.  If you are worried about Putin please bounce this off your senator.

Breathe safely.

Stephen

 

 

 

From: geoengi...@googlegroups.com <geoengi...@googlegroups.com> On Behalf Of Gideon Futerman
Sent: 26 July 2022 16:21
To: geoengineering <geoengi...@googlegroups.com>
Subject: Re: [geo] Nuclear Winter and SRM (including termination shock)

 

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[Douglas MacMartin]

The timescales of response to turning off SRM are overwhelmingly dominated by climate system time constants, and not by the residence time of aerosols used for SAI or MCB.  There’s no question about the sign of the effect (that the termination shock from MCB would be more rapid, which in this context would be a good thing, and in other contexts a bad thing), but I would expect that’ll be a pretty small difference.

 

Regardless, at least in the first couple of years, the delta-T from nuclear winter will be smaller if at the same time SRM is being turned off, so initially the climate impacts are reduced if the nuclear winter occurred in a world with SRM.  And I agree with what’s been said before – if the nuclear war is sufficiently bad that one can’t restart SRM in a few years, then my guess would be that the real problem is the nuclear war…

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[Renaud de RICHTER]

I have problems imagining which global catastrophe will provoke an unintended termination shock from MCB if the some hundred ship vessels are located half year in one hemisphere, and the other half on the other. I believe that with 5 to 10% excess ships you can deal with the replacement of the ones needing repair or maintenance. 

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[Daniele Visioni]

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,

To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/419bee77-0d9a-416a-9b38-5fc6f584ba3cn%40googlegroups.com.

[Andrew Lockley]

I'm not sure I agree with the framing that is being used here. We do not have to imagine a global cataclysm. Alternatively we could imagine that India is the only country engaging in geoengineering, and it engages in a locally catastrophic but limited war with Pakistan. In this case, we could consider a situation where the global economy was suffering little Direct damage, but there was a nuclear winter as a result of large urban fires. If both geoengineering hardware and know how is lost in the war, termination shock occurs simultaneously with nuclear winter. That might serve to hasten and worsen the sudden change in temperature coming out of a nuclear winter leading to a nuclear summer

A

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[Michael MacCracken]

There is a real question about how much smoke an India-Pakistan conflict could generate and loft. So, in a normal scenario, one shoots one's weapons at the other sides offensive weapons (missiles, control systems, maybe fuel storage locations, etc.) and not clear (at least to me) that this could create a hot enough fire to really loft much smoke--lighting the Kuwait oil fields did not really loft much, in part due to the typical inversion that prevails. Were the cities attacked, it is also just not clear there is enough burnable material to loft smoke, given wood is not a typical building material, at least in areas I have visited. And a war during the monsoon season would also not seem likely to loft much smoke. Might one hae enough to affect the weather--perhaps, but the thermal capacity of the oceans is very large and I'd suggest it would take a lot more smoke than that to cause a significant effect.

Mike MacC

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[Gideon Futerman]

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:

[Gilles de Brouwer]

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      

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[Gideon Futerman]

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

[kevin lister]

Dear Gideon,

 

I think that you are grabbing the wrong end of the stick.

 

The problem is that once nations have nuclear arsenals and are engaged in nuclear weapons races which require competing military industrial complexes and permanently expanding economies to fund these then there is an unstoppable commitment to increasing fossil fuel consumption. Ironically, the worse that climate change gets, the more nations will seek protection under their nuclear umbrellas and the more nations will resort to conventional war.

 

Thus nuclear weapons and the arms races they drive become the biggest cause of climate change and the resulting climate change lowers the threshold for nuclear war, as Renaud points out below.  Once we have nuclear war, as everyone has pointed out debates about SRM are irrelevant.

 

The question now is how do we link security and climate change commitments in a world where competing nations have all adopted first strike responses with nuclear weapons. My view is that unless we have a modern day Baruch Agreement to do this will not succeed and this is not even on any agenda.  My past calculations using game theory and which I have supported with modelling indicate the chance of success without such an agreement is 1E-63. That is considerably less than finding a single atom on the plant in a random selection.

 

Under this interpretation, commitments to high carbon emissions and eventual nuclear war are extremely high probability outcomes with current political system.

 

Kevin

 

 

 

Sent from Mail for Windows

 

From: Gideon Futerman
Sent: 27 July 2022 12:44
To: geoengineering
Subject: Re: [geo] Nuclear Winter and SRM (including termination shock)

 

Hi all,

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: rob...@envsci.rutgers.edu
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?

 

 

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[Andrew Lockley]

To address nuclear winter, consider this paper, Daniel Heyen, Joshua Horton, and Juan Moreno-Cruz. 3/20/2019. “Strategic implications of counter-geoengineering: Clash or cooperation?” Journal of Environmental Economics and Management, 95, Pp. 153-177.

This offers a possible way out. Equipment to release short lived climate forces could be ruggedised, making it largely impervious to nuclear war - for example, by releasing gases into deep caves, which slowly find their way into the atmosphere. 

Similarly, as the nuclear winter ends and termination shock becomes an issue (a nuclear summer), consider this paper. 

An approach to sulfate geoengineering with surface emissions of carbonyl sulfide

Ilaria Quaglia et al.

https://acp.copernicus.org/articles/22/5757/2022/acp-22-5757-2022-assets.html

This offers very similar technology for warming, which could be again set up in deep caves, impervious to nuclear weapons. 

Such systems could be designed with a "dead man's handle" control system - in that they automatically release without intervention, either if not manually reset or if a pressure drop or electromagnetic / seismic pulse is detected, indicating a nuclear strike. 

A

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[Douglas MacMartin]

Of course there are more minor conflicts possible with less severe outcomes… though if it’s a regional war that doesn’t itself end civilization, I don’t see why one couldn’t restart SRM in a year or two if desired.

 

Gideon, you write: “I understand why there is aversion to me exploring such risks;” I think you misunderstand everyone’s response here.  It isn’t an aversion to exploring them, nor a belief that we don’t need to look at extreme but less likely scenarios, but rather, that this specific risk doesn’t seem to many of us like there’s anything that needs to be explored.  That is, my view, and I think others, is that any nuclear war severe enough to result in losing the ability to even restart SRM is so severe that the nuclear war + termination isn’t appreciably worse than the nuclear war itself.

 

I 100% agree with the need to think through low probability but high impact possibilities.

 

d

 

From: geoengi...@googlegroups.com <geoengi...@googlegroups.com> On Behalf Of Gilles de Brouwer
Sent: Tuesday, July 26, 2022 11:11 PM
To: ggfut...@gmail.com
Cc: Daniele Visioni <daniele...@gmail.com>; geoengineering <geoengi...@googlegroups.com>
Subject: Re: [geo] Nuclear Winter and SRM (including termination shock)

 

FYI   Updated nuclear winter analysis is so much worse than SAI that it's pointless to consider.

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: rob...@envsci.rutgers.edu
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?

 

 

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[Gideon Futerman]

Hi Doug,

Apologies for misinterpreting. Its a statement like this that I have been looking for.

When you suggest it isn't appreciably worse, is that a suggestion that either:

- The death toll/ the ability for society to recover would be no different given the double catastrophe than the single catastrophe

- The climatic response to the double catastrophe is no different than the single catastrophe

- The difference in death toll may be, say (and these are made up numbers) 6 billion vs 6.01 billion

Thank you so much for the clarification

Best

Gideon

[Douglas MacMartin]

All of the above, with qualifiers… yes the climatic response would be different, but personally I think 6B dead is so bad that whether it’s 6.01 or 6.1 or 6.5 isn’t something that I feel matters particularly (nor do I think it is particularly answerable).  What decisions would depend on the answer to that question? 

[Andrew Lockley]

If you consider the residual human population, the difference is huge. Losing 0.1 of the last billion people alive would be losing 10pc of the entire global population. Further, that might not be evenly distributed. For example, it might mean the death of all - or almost all - of the surviving people in the Indian subcontinent. Such concentrated additional deaths would be a genetic and cultural catastrophe for the remnants of the human race.

I think it would be complacent to dismiss Gideon's concerns. Much of interest may be revealed by modelling such clustered catastrophes. Some of the results may give us answers to questions not yet asked.

In general, I think considering stacked disasters is wise. We currently have several linked minor disasters - a regional war, a fuel price shock and the beginning of a global famine. A small nuclear war on top is unlikely, but it would be a brave man to argue it was impossible. While these issues have a common cause, they aren't the same thing.

A

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[Gideon Futerman]

I think this is going to get into more general philosophy/ethics around Existential Risks, Longtermism and Global Catastrophic Risks, which whilst interesting and useful, probably a bit orthogonal to what people are turning to the geoengineering google group for. But basically, a difference between 6 billion and say 6.1 billion or 6.5 billion is firstly important from the perspective of deaths: that's still 100 million people. Secondly, climatic effects, excess deaths on top of the nuclear winter (or reduced severity!)  etc are potentially relevant for whether it will "only" kill 6 billion and whether it will lead to irrecoverable (not merely awful) societal collapse, which from various longtermist perspectives is very bad. Given how hard it would be to recover anyway, a "double catastrophe" could make recovery much harder distinguish between a  Global Catastrophic Risk and an existential risk, which from various philosophical viewpoints is very important.

Thus, such a question ie whether SRM might increase/decrease the likelihood of a global catastrophic risk being converted to an existential risk (due to this Latent Risk of termination shock we have been discussing) is of serious interest to many people, including potentially major funders who are potentially interested in investing in SRM research. In that sense, this impacts some potentially very important decisions for the future of our field, and the distinction between 6 billion and say 6.5 billion, or  even if it just makes societal recovery 10% less likely to happen, it may be absolutely vital. I am happy to explain this in more depth if people need, although what I was really wanting to ask the list for was fundamentally a question of physical science to try and answer this application. 

Even if none of this has convinced you of the moral importance of it, the question I was asking was fundamentally a physical one, responding to a scientific assumption in Baum et al 2013 that I thought seemed potentially unsound (that under nuclear war termination shock would lead to a double catastrophe and not a slight softening of the first catastrophe). Given that paper is one of only a handful papers published in this intersection between SRM and Global Catastrophic Risk studies, such a claim is, even from a physical/empirical rather than moral viewpoint, important to test. Hence why I have posed this question.

[Douglas MacMartin]

I agree that the sign of the effect is unclear in addition to the magnitude, that is, nuclear winter + termination is “better” at first than nuclear winter alone, but “worse” afterwards if it is impossible to restart; that of course is all contingent on how bad the nuclear winter is, how much cooling is being offset, and your beliefs about how the use of SRM does or doesn’t affect mitigation (that is, the circumstances in which termination materially affects outcomes are those in which SRM is being used to offset significant warming – so from a risk perspective, if the counterfactual is that much warmer world, or the counterfactual a world that had more mitigation, is essential).

 

I agree that as researchers we should try to inform decisions, and hence risks, and be responsive to stakeholder concerns.  In this case, I think the *much* bigger influence of SRM on nuclear winter comes from whether it increases or decreases the risks of nuclear war, and what we can do in terms of governance to affect that…

[Gideon Futerman]

Thanks for the useful feedback and responses to this question everyone. Its not an area I have expertise in, so the feedback has been exceptionally useful,

Kind Regards

Gideon

[Russell Seitz]

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  1June2022

The Climate and Ozone Impacts of Black Carbon Emissions From Global Rocket Launches

Christopher M Maloney, Robert W Portmann, Martin N Ross, Karen H Rosenlof

 

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.

[Gideon Futerman]

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

[Gideon Futerman]

It would be good to know if something about my calculations here are fundamentally wrong. I am no aerosol expert by any margins, and as seen, my model is pretty much the most simple possible thing that I could make on this, but it does seem to give an indication against the "double catastrophe" thesis. Please let me know if I am wrong on this