The exposition scientist lady in the lab coat near the beginning of the movie is explaining how reverse entropy works to the Protagonist, and one of the things she says specifically is;
"The specter of nuclear weapons is poised to effect our future, but an inverted nuclear bomb could effect our past."
Or something very close to that.
This was after she told him how inverted bullets work in relation to reverse entropy, and how ionizing radiation somehow takes effect if one is harmed by an inverted round. She went on to tell him how if a brass casing, a lead projectile, and gunpowder can be inverted, then she imagines ANYTHING can be.
Nolan is a slick story teller, even if this movie is convoluted as fuck. He had the scientist woman tell the Protagonist "not to think about it too much" as a way to cover his tracks with the viewer, as to say, dont try to look too far into it, because it will TOTALLY not make fucking any sense the more you unpack it. And its true.
If you just ride with the flow of the film, and take what it gives you, the surface concepts are amazing. The entire premise of inverted weapons being able to effect the past is mind blowing. The amount of lore and different concepts one can explore when looking at how inverted weapons and objects could shift events that already happened is so vast, you cant have enough ideas.. The slickest, and most effective part of the plot was when The Protagonist was fighting himself in the swat suit. When its revealed he was fighting himself, it has a real impact, as it is a very interesting angle, and is something that is completely original. (in the way it was executed) The best part for me was seeing what would happen if a highly skilled fighter fought his mirror image, it was basically a complete wash as they both anticipated each others attacks and almost fought to a stalemate.
But when you start to dig deeper and look at how guys would get stuck in a reverse exploding wall, and how instinct can have an effect on inverted objects, which apparently are only inverted if put through "turn-styles" which is where everything begins to fall apart, and therefor Im done.
edit: And yeah lol, I didnt even really consider your question Zweischneid. If a regular inverted explosion caused a reverse effect and things freeze, then wouldnt an inverted nuclear explosion have a similar opposite effect? Like would it result in an Ice Age? LOL.