If there were a nuclear war would there be an after thereafter? How far does radiation drift?
If a war were confined to the Pacific area would the rest of the world be safe from the effects or would everyone die in time from radiation poisoning? Who else would get involved if the war started between the US and North Korea?
There have been 520 "atmospheric" nuclear tests starting with Project Trinity so there's plenty of data that can be used to project that kind of thing.
But it will be a home run for the progressive globalists out there. All that dust blasted into the stratosphere will cause a "nuclear winter" (doubtful, really) that will reduce "global warming" and between the direct effects and the residual radiation it will reduce the global population.