Some of those people who are likely to have a really bad time have nukes. India and Pakistan, for example. They both depend on water from Himalayan glaciers.
If they get in a war over dwindling water and it goes nuclear, the effects could be felt globally. Ironically, a big effect could be global cooling, which would set crop yields around the world plummeting. That would only last for a few years, maybe 10 tops, and then we'd be back to warming, but a hell of a lot of people would have died due to widespread famine during that time.
China also makes heavy use of Himalayan glacier water, but I don't think they'd nuke anyone over it. A few other countries also depend on the glaciers, but India, Pakistan, and China are the only ones with nukes.
I don't think that an India-Pakistan nuclear conflict has the potential to lead to a global cooling effect.
All the nuclear doomsday scenario estimates are based on the cold war NATO-Warsaw Pact nuke arsenals, where something like 30000 warheads might have been fired. That's a huge number of nukes, the world does not have nearly as much nukes now, and even less so for the smaller powers (90% of all nukes are held by USA and Russia).
India and Pakistan together have ~300 warheads; if India and Pakistan blow all their nukes, that's comparable to something like two years worth of nuclear weapons testing back in the 1960s, and the 1960s tests were nowhere close to triggering a worldwide famine.
It's the firestorms afterwards that cause climate problems. Most above ground tests were not in places that led to big firestorms.
See the paper "A regional nuclear conflict would compromise global food security", PNAS March 31, 2020 117 (13) 7071-7081 [1]. Here's an article about it [2].
They are looking at a war with 100 Hiroshima-sized detonations in the most populated urban areas of India and Pakistan.
Yes, that's a good point - the global cooling effect IIRC was largely based on the emissions from burning cities, not the direct effects of nuclear explosions. Still, in an India-Pakistan war there would be much less burning cities than in the hypothetical cold war turning hot, which would burn the urban areas of the whole northern hemisphere.
It's a bit weird to guesstimate about so horrible hypothetical events, but perhaps the consequences of such a war might be comparable to all the many cities burned in firebombing and otherwise during WW2 - which, again, did not trigger a global cooling that might threaten global agriculture.
If they get in a war over dwindling water and it goes nuclear, the effects could be felt globally. Ironically, a big effect could be global cooling, which would set crop yields around the world plummeting. That would only last for a few years, maybe 10 tops, and then we'd be back to warming, but a hell of a lot of people would have died due to widespread famine during that time.
China also makes heavy use of Himalayan glacier water, but I don't think they'd nuke anyone over it. A few other countries also depend on the glaciers, but India, Pakistan, and China are the only ones with nukes.