Well, the possibility is largely conjecture and extrapolation on my part. It's been established that one result of even a limited regional nuclear war would be a cooling climate, but a climate cooling way too much, in addition to other meteorological effects. See:

https://www.washingtonexaminer.com/opinion/how-a-nuclear-war-between-india-and-pakistan...

https://www.nationalgeographic.com/news/2011/2/110223-nuclear-war-winter-global-warming...

OK, those aren't hard core scientific publications, but I assume they're based on sound science. If so, then wouldn't a much, much smaller exchange have the potential to cool the climate to a desired degree?

And here's another disturbing aspect of a planned war. The agreeing parties could essentially pick their own targets, meaning, literally, their own targets! I'm guessing Trump would pick Chicago as a recipient of a small nuclear device. Or Detroit. Xi would pick whatever city is being the biggest pain in the ass for one reason or another.

So in one swoop lasting less than 24 hours, they could eliminate local threats to their power and address global warming. This would allow them to continue using fossil fuels. It would save the Aramcos of the world who are currently shitting their pants and fearing obsolescence. Whoa! What do you mean I can't buy MBS Junior a Ferrari this year? It's a win win for all the old farts who are currently losing!

EDIT for links:

https://www.npr.org/2020/01/29/800938203/u-s-has-deployed-new-small-nukes-on-submarine-...

https://www.japantimes.co.jp/news/2020/08/07/world/politics-diplomacy-world/russia-warn...