I agree it’s very unlikely that a nuclear war discharging current arsenals could directly cause human extinction. But the conditional probability of extinction given all-out nuclear war can go much higher if the problem gets worse. Some aspects of this:
-at the peak of the Cold War arsenals there were over 70,000 nuclear weapons, not 14,000 -this Brookings estimate puts spending building the US nuclear arsenal at several trillion current dollars, with lower marginal costs per weapon, e.g. $20M per weapon and $50-100M all-in for for ICBMs -economic growth since then means the world could already afford far larger arsenals in a renewed arms race -current US military expenditure is over $700B annually, about 1/30th of GDP; at the peak of the Cold War in the 50s and 60s it was about 1/10th; Soviet expenditure was proportionally higher -so with 1950s proportional military expenditures, half going to nukes, the US and China could each produce 20,000+ ICBMs, each of which could be fitted with MIRVs and several warheads, building up to millions of warheads over a decade or so; the numbers could be higher for cheaper delivery systems -economies of scale and improvements in technology would likely bring down the per warhead cost -if AI and robotics greatly increase economic growth the above numbers could be increased by orders of magnitude -radiation effects could be intentionally greatly increased with alternative warhead composition -all-out discharge of strategic nuclear arsenals is also much more likely to be accompanied by simultaneous deployment of other WMD, including pandemic bioweapons (which the Soviets pursued as a strategic weapon for such circumstances)and drone swarms (which might kill survivors in bunkers); the combined effects of future versions of all of these WMD at once may synergistically cause extinction
This may be in the Brookings estimate, which I haven’t read yet, but I wonder how much cost disease + reduction in nuclear force has affected the cost per warhead / missile. My understanding is that many military weapon systems get much more expensive over time for reasons I don’t well understand.
Warheads could be altered to increase the duration of radiation effects from fallout, but this would would also reduce their yield, and would represent a pretty large change in strategy. We’ve gone 70 years without such weapons, which the recent Russian submersible system as a possible exception. It seems unlikely such a shift in strategy will occur in the next 70 years, but like 3% unlikely rather than really unlikely.
It’s a good point that risks of extinction could get significantly worse if different/more nuclear weapons were built & deployed, and combined with other WMDs. And the existence of 70k+ weapons in the cold war presents a decent outside view argument that we might see that many in the future. I’ll edit the post to clarify that I mean present and not future risks from nuclear war.
Having in mind those considerations, do you have a guess for what is the probability that one or more incidents involving nuclear weapons will cause human extinction by the end of 2100?
Alone and directly (not as a contributing factor to something else later), enough below 0.1% that I evaluate nuclear interventions based mainly on their casualties and disruption, not extinction. I would (and have) support them in the same kind of metric as GiveWell, not in extinction risk.
In the event of all-out WMD war (including with rogue AGI as belligerent) that leads to extinction nukes could be a contributing factor combined with bioweapons and AI (strategic WMD war raises the likelihoods of multiple WMDs being used together).
I agree the direct/nearterm extinction risk posed by nuclear war alone would be quite low (maybe of the order of 10^-6 in the next 100 years), but I wonder whether it could still meaningfully decrease the value of the longterm future if thousands of nukes are detonated. Models S and E of Denkenberger 2022 consider a full scale nuclear war would decrease such value by 24 % and 7 %. I think these are too high, but guess a nuclear war involving thousands of nukes might still increase indirect/longterm extinction risk to a significant extent. So I would say they are not directly comparable to GiveWell’s top charities.
I agree it’s very unlikely that a nuclear war discharging current arsenals could directly cause human extinction. But the conditional probability of extinction given all-out nuclear war can go much higher if the problem gets worse. Some aspects of this:
-at the peak of the Cold War arsenals there were over 70,000 nuclear weapons, not 14,000
-this Brookings estimate puts spending building the US nuclear arsenal at several trillion current dollars, with lower marginal costs per weapon, e.g. $20M per weapon and $50-100M all-in for for ICBMs
-economic growth since then means the world could already afford far larger arsenals in a renewed arms race
-current US military expenditure is over $700B annually, about 1/30th of GDP; at the peak of the Cold War in the 50s and 60s it was about 1/10th; Soviet expenditure was proportionally higher
-so with 1950s proportional military expenditures, half going to nukes, the US and China could each produce 20,000+ ICBMs, each of which could be fitted with MIRVs and several warheads, building up to millions of warheads over a decade or so; the numbers could be higher for cheaper delivery systems
-economies of scale and improvements in technology would likely bring down the per warhead cost
-if AI and robotics greatly increase economic growth the above numbers could be increased by orders of magnitude
-radiation effects could be intentionally greatly increased with alternative warhead composition
-all-out discharge of strategic nuclear arsenals is also much more likely to be accompanied by simultaneous deployment of other WMD, including pandemic bioweapons (which the Soviets pursued as a strategic weapon for such circumstances)and drone swarms (which might kill survivors in bunkers); the combined effects of future versions of all of these WMD at once may synergistically cause extinction
This may be in the Brookings estimate, which I haven’t read yet, but I wonder how much cost disease + reduction in nuclear force has affected the cost per warhead / missile. My understanding is that many military weapon systems get much more expensive over time for reasons I don’t well understand.
Warheads could be altered to increase the duration of radiation effects from fallout, but this would would also reduce their yield, and would represent a pretty large change in strategy. We’ve gone 70 years without such weapons, which the recent Russian submersible system as a possible exception. It seems unlikely such a shift in strategy will occur in the next 70 years, but like 3% unlikely rather than really unlikely.
It’s a good point that risks of extinction could get significantly worse if different/more nuclear weapons were built & deployed, and combined with other WMDs. And the existence of 70k+ weapons in the cold war presents a decent outside view argument that we might see that many in the future. I’ll edit the post to clarify that I mean present and not future risks from nuclear war.
Hi Carl,
Having in mind those considerations, do you have a guess for what is the probability that one or more incidents involving nuclear weapons will cause human extinction by the end of 2100?
Alone and directly (not as a contributing factor to something else later), enough below 0.1% that I evaluate nuclear interventions based mainly on their casualties and disruption, not extinction. I would (and have) support them in the same kind of metric as GiveWell, not in extinction risk.
In the event of all-out WMD war (including with rogue AGI as belligerent) that leads to extinction nukes could be a contributing factor combined with bioweapons and AI (strategic WMD war raises the likelihoods of multiple WMDs being used together).
Thanks for the reply!
I agree the direct/nearterm extinction risk posed by nuclear war alone would be quite low (maybe of the order of 10^-6 in the next 100 years), but I wonder whether it could still meaningfully decrease the value of the longterm future if thousands of nukes are detonated. Models S and E of Denkenberger 2022 consider a full scale nuclear war would decrease such value by 24 % and 7 %. I think these are too high, but guess a nuclear war involving thousands of nukes might still increase indirect/longterm extinction risk to a significant extent. So I would say they are not directly comparable to GiveWell’s top charities.
Maybe you think they are comparable given the low likelihood of civilisation collapse, and the flow-through effects of saving lives (which might include decreasing longterm extinction risk)?