It turns out (and I didn't realize this until I looked back into it just a few years ago) that the 70s/80s concept of nuclear winter is discredited and believed not to be something that would arise from a global thermonuclear holocaust.

On the contrary, modern research shows that the effects would be more severe and long-lasting: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2006jd00...