I guess you're talking about "nuclear winter", where the ash from the nuclear explosions gets into the upper atmosphere, blocks some of the sunlight and leads t

I guess you're talking about "nuclear winter", where the ash from the nuclear explosions gets into the upper atmosphere, blocks some of the sunlight and leads to a global famine. I'm not sure what's "a small number of nukes" in your book. Last I read about it, estimates suggest e.g. India and Pakistan dropping their entire arsenals on each other would indeed cause a nuclear winter.