I'm not fear-mongering; I'm just a pessimist. My scenarios are “unbelievably unrealistic” and “apocalyptic sci-fi”, respectively, but I wanted to make sure I go

I'm not fear-mongering; I'm just a pessimist. My scenarios are “unbelievably unrealistic” and “apocalyptic sci-fi”, respectively, but I wanted to make sure I got an upper bound on the worst-case. I don't know much about the topic, so I had to go into “I know this is unrealistic” territory for that. See also: https://xkcd.com/2261/ https://xkcd.com/2261/ and https://xkcd.com/883/ https://xkcd.com/883/.