We are indeed writing something on this (sorry it is taking so long!). I would dispute your characterization of the principle contributor of climate change to nuclear war though. Working on Barrett and Baum’s recent model of how nuclear war’s might occure I would argue that the greatest threat from climate change is that it creates conditions under which a prec[ititating event such as a regional war might escalate into a nuclear conflict are more likely—i.e. it increases our vulnerability to such threats. This is probably more significant than its direct impact on the number of precipitating events. Since such events are not actually that uncommon (Barret and Baum find over 60 I seem to remember whilst a Chatham House survey found around 20) I think that any increase in our vulnerability to these events would not be insignificant.
What is certainly correct is that the nature of the threat posed by climate change is very different in many ways to that posed by AI. Indeed the pathways from threat to catastrophe for anything other than AI (including pandemics, nuclear weapons, asteroids and so on) are generally complex and circuitous. On the one hand that does make these threats less of a concern because it offers multiple opportunities for mitigation and prevention. However, on the other hand, it makes them harder to study and assess, especially by the generally small research teams of generalists and philosophers who undertake the majority of x-risk research (I am not patronising anyone here, that is my background as well).
What would be the mechanism whereby it increases the risk of nuclear war? The main one I can think of is mass migration, but I’m not sure what the proposed mechanism is. Are there analogues in the past for comparably large mass migrations causing wars or increased nuclear tensions? We’ve had quite large refugee flows recently, but this seems to have had basically no impact on nuclear tensions. Given that the main worry for nuclear winter is US-Russia conflict, how could climate change exacerbate tensions there?
I also think it would be surprising if there had been 60 genuine near misses in the past, but that is another debate. That suggests surprising levels of luck. The Tertrais et al paper questions some claims about nuclear near misses
I think we might disagree about what constitutes a near miss or precipitating event. I certainly think that we should worry about such events even if their probability of leading to a nuclear exchange are pretty low (0.001 lets say) and that it would not be merely a matter of luck to have had 60 such events and no nuclear conflict, it is just that given the damage such a conflict would do they still reprasent an unaceptable threat.
The precise role played by climate change in increasing our vulnerability to such threats depends on the nature of the event. I certainly think that just limiting yourself to a single narrative like migration —> instability —> conflict is far to restrictive.
One of the big issues here is that climate change is percieved as posing an existential threat both to humanity generally (we can argue about the rights and wrongs of that, but the perception is real) and to specific groups and communities (I think that is a less contraversial claim). As such I think it is quite a dangerous element in international relations—especially when it is combined with narratives about individual and national reponsibility, free riding and so on. Of course you are right to point out that climate change is probably not an existential threat to either the USA or Russia but it will be a much bigger problem for India and Pakistan and for client states of global superpowers.
What do you make to the argument that the probability of nuclear winter caused by climate change is considerably lower than the probability of nuclear winter, so focusing more directly on nuclear winter looks a better bet?
Of course it will be smaller, however that does mean that tackelling climate change will not make a sizeable contribution towards reducing the risk of nuclear winter. The question for me is whether nuclear winters that relate to climate change are more or less tractable than nuclear winter as a whole. My view would be that trying to reduce the risk of nuclear winter by tackelling climate change and its consequences may be a more tractable problem then doing so by trying to get nuclear weapons states to disarm or otherwise making nuclear war less likely in general, but that efforts to make nuclear winter more survivable are probably more efficient than either of these policies from a purely x-risk reduction perspective.
However, I also do not think that nuclear winter is the only way in which climate change may lead to an existential threat (at least reading existential threat to include the prospect for an unrecoverable from civilisational collapse) as there are some interesting feedback loops between environmental and social collapse that have the potential to cause non-linear and self-perpetuating shifts in the structure of global civilisation. Admittedly these are hard to study, but from a value maximisation perspective I would say that in the face of uncertainty we will do better if we assume that global civilisation is relatively fragile to such changes than if we assume that it is more robust to them.
I don’t agree that working on climate change is plausibly a better way to reduce the risk of nuclear war than working directly on nuclear war. Firstly, climate change is a very intractable problem in the first place for philanthropists and for national governments, given that action is opposed by entrenched interests across all society and requires cooperation pretty much of all nations. Nuclear peace is opposed by some entrenched interested in the military industrial complex, but these do not reach anywhere near as far into society as a whole. Major results could be achieved just by getting cooperation between Russia and US, which is not true of climate change.
Secondly, climate change is much less neglected than reducing the risk of nuclear war. Thirdly, there have been lots of apparently successful treaties that have e.g. limited the size of US and Russian arsenals. It just seems much easier to make progress on things that foster peace and reduce arsenals than on nuclear war caused by climate change. The path for the latter is extremely indirect.