I think this is plausible, but less obvious than you imply. Some reasons to doubt your conclusions:
A common mistake in forecasting/counterfactual reasoning is to imagine a world in which X is different, and then imagine the direct effects that that difference would have if everything else would held constant—in particular, if no one too active countermeasures. In this case, some countermeasures that might be taken in a world with far more nuclear proliferation include:
Stronger systems of global governance
More vigorous promotion, verification, enforcement, etc. of nuclear weapons related treaties, or just norms/policies like counterforce targeting, no first use, etc.
More development and deployment of missile defence systems
More shelters, refuges, etc.
Changes in how cities are designed to make them more resilient to nuclear strikes
More vigorous development of food sources that could be used even in nuclear winter scenarios, e.g. the kind ALLFED looks into
More vigorous crackdowns on terrorism, or especially the kinds of terrorist groups that might have the means and desire to seize and use nuclear weapons
(I’m not necessarily saying that any one of these things would be likely or that it’d be sufficient by itself to massively reduce the harms of a nuclear strike. But I do think it’s likely that some countermeasures would be engaged in, and would at least somewhat reduce the harms.)
It’s not obvious that a nuclear strike would even lead to retaliation by the struck party, let alone a chain reaction that brings in other parties
I’m not saying that that definitely wouldn’t happen, but it’s just not obvious why it would, without further arguments/modelling and probably a bunch of specifics
Nuclear exchanges aren’t guaranteed to cause nuclear winter
Those are some valid points; more generally I’ll admit that I might have been jumping the gun/overselling it a bit (in retrospect I think that many small-level regional exchanges may not spark a chain reaction if the world restructured the international system to avoid chain gang alliances). However, I still think it’s more likely that nuclear catastrophe would occur than not by 2020.
In part, I think it depends on how you set up this counterfactual: if we are talking about a world in which everyone goes to sleep one night in 1960, then they wake up and surprise every state now magically has a nuclear arsenal—i.e., the counterfactual status/event wasn’t brought about by the intentions of states in the counterfactual world—then I think the chances for peace are reasonable, because most states probably didn’t want that event/status in the first place. However, if the counterfactual is one where almost all the states now have nuclear weapons because they sought out the nuclear weapons and were easily able to acquire them, etc. (which is the assumption I was operating on), I would expect that coordination would be much more difficult. As it is, I think that the fact that states around the world were willing to get nuclear weapons is indicative that they don’t trust/won’t abide by “global governance” (or, more directly, that “global governance” is ineffective).
More generally, I think that people might be overestimating the ability for some 100+ states to coordinate when there are no global superpowers: who sets the rules? Who enforces the rules? Who enforces the enforcement? Collective action problems in international affairs have been hard enough even when we were in a bipolar and unipolar system; enforcing anti-terror laws and related provisions may get a lot easier with collective buy-in (even would-be state sponsors of terrorism would be extremely worried that their proxies may disobey orders or even turn on their masters), but if we are talking about verifying arms control treaties, investigating accidental (?) detonations, retaliating against first-uses, and other actions where states may have a vested interest in opposing the proceedings, rule-setting and enforcement can become very difficult tasks.
I think this is plausible, but less obvious than you imply. Some reasons to doubt your conclusions:
A common mistake in forecasting/counterfactual reasoning is to imagine a world in which X is different, and then imagine the direct effects that that difference would have if everything else would held constant—in particular, if no one too active countermeasures. In this case, some countermeasures that might be taken in a world with far more nuclear proliferation include:
Stronger systems of global governance
More vigorous promotion, verification, enforcement, etc. of nuclear weapons related treaties, or just norms/policies like counterforce targeting, no first use, etc.
More development and deployment of missile defence systems
More shelters, refuges, etc.
Changes in how cities are designed to make them more resilient to nuclear strikes
More vigorous development of food sources that could be used even in nuclear winter scenarios, e.g. the kind ALLFED looks into
More vigorous crackdowns on terrorism, or especially the kinds of terrorist groups that might have the means and desire to seize and use nuclear weapons
(I’m not necessarily saying that any one of these things would be likely or that it’d be sufficient by itself to massively reduce the harms of a nuclear strike. But I do think it’s likely that some countermeasures would be engaged in, and would at least somewhat reduce the harms.)
It’s not obvious that a nuclear strike would even lead to retaliation by the struck party, let alone a chain reaction that brings in other parties
I’m not saying that that definitely wouldn’t happen, but it’s just not obvious why it would, without further arguments/modelling and probably a bunch of specifics
Nuclear exchanges aren’t guaranteed to cause nuclear winter
This topic is still subject to lots of debate
See e.g. this post
(I don’t like the title, and I think Max Daniel’s comment should be read alongside the post, but the post’s analysis still seems useful to me)
Nuclear winter isn’t guaranteed to cause civilizational collapse
See also https://forum.effectivealtruism.org/posts/pMsnCieusmYqGW26W/how-bad-would-nuclear-winter-caused-by-a-us-russia-nuclear
(And also collapse might be recovered from)
Those are some valid points; more generally I’ll admit that I might have been jumping the gun/overselling it a bit (in retrospect I think that many small-level regional exchanges may not spark a chain reaction if the world restructured the international system to avoid chain gang alliances). However, I still think it’s more likely that nuclear catastrophe would occur than not by 2020.
In part, I think it depends on how you set up this counterfactual: if we are talking about a world in which everyone goes to sleep one night in 1960, then they wake up and surprise every state now magically has a nuclear arsenal—i.e., the counterfactual status/event wasn’t brought about by the intentions of states in the counterfactual world—then I think the chances for peace are reasonable, because most states probably didn’t want that event/status in the first place. However, if the counterfactual is one where almost all the states now have nuclear weapons because they sought out the nuclear weapons and were easily able to acquire them, etc. (which is the assumption I was operating on), I would expect that coordination would be much more difficult. As it is, I think that the fact that states around the world were willing to get nuclear weapons is indicative that they don’t trust/won’t abide by “global governance” (or, more directly, that “global governance” is ineffective).
More generally, I think that people might be overestimating the ability for some 100+ states to coordinate when there are no global superpowers: who sets the rules? Who enforces the rules? Who enforces the enforcement? Collective action problems in international affairs have been hard enough even when we were in a bipolar and unipolar system; enforcing anti-terror laws and related provisions may get a lot easier with collective buy-in (even would-be state sponsors of terrorism would be extremely worried that their proxies may disobey orders or even turn on their masters), but if we are talking about verifying arms control treaties, investigating accidental (?) detonations, retaliating against first-uses, and other actions where states may have a vested interest in opposing the proceedings, rule-setting and enforcement can become very difficult tasks.