I'm not sure specifically about IndoPak nuclear war, but I think the general drift of this post is important - lots of Xrisk comes from factors we haven't thought extensively about (I don't think this particular area has come up on LW before).
There are two models for thinking about Xrisk. In the first model, which I associate with SIAI, most Xrisk comes from a small number of enumerable threats: uFAI, asteroid impact, etc. In this model, to prevent extinction, one should consider each threat in turn and design measures to protect against each.
In the second model, which I personally favor, the majority of Xrisk is distributed among a large number of threats. Each individual threat is highly improbable*, but because such threats are so numerous, net Xrisk is significant. In this model, it is impractical to design specialized defenses against specific threats. Instead, one should design countermeasures that protect against entire categories of threats.
* More precisely, the events may be probable but the likelihood of the event causing existential disaster is very low. IndoPak nuclear was is moderately probable, but it seems highly unlikely that such a war could pose a serious threat to human survival.
Last month I was involved in a conversation thread about what the impact of a hypothetical nuclear war would be on existential risk.
There are many potential nuclear war scenarios which would have varying impacts on existential risk. It's difficult to know where to start to gain an understanding of the long-term of nuclear proliferation.
For concreteness, consider the case of an India-Pakistan nuclear war.
According to Local Nuclear War, Global Suffering by Robock and Toon,
[...]
Note that this would presumably cause some degree of chaos in the developed world.
I have not yet investigated the credibility of the papers' claims. However,
Suppose that an all-out nuclear war between India and Pakistan were to occur and were to result in climate change killing 1 billion people. Then would the probability of a positive singularity increase or decrease and if so why?
This question seems very difficult to answer; maybe altogether too difficult for humans to answer. I welcome responses raising relevant considerations even in absence of a good way to compare the relevant considerations. Please read the linked conversation thread before commentating.