I think they’re referring to the nuclear waste accident in 2019 that bifurcated the timeline in 1984 allowing 1983’s events to continue uninterrupted
So that’s what the thermonuclearhaline is.
Dark and/or 1983 reference?
It’s Dark!
The question is not where, or who, or how, but rather when
Or even Counterpart?
Interesting, never heard of that. Or maybe I did, but as it's presumably worse than 1983 and Dark I skipped it.
Edit: It's actually mentioned in my files, so I had heard of it.