Well, a full nuclear exchange between the U.S. and Russia would end civilization as we know it. Though it is unlikely to wipe out the human race entirely, we'd

Well, a full nuclear exchange between the U.S. and Russia would end civilization as we know it. Though it is unlikely to wipe out the human race entirely, we'd be reduced to paleolithic population levels and it's really hard to predict how things would develop from there. A nuclear exchange between the U.S. and China, or between India and Pakistan on the other hand would cause a decades-long crisis, but wouldn't outright destroy civilization in the way a U.S.-Russia exchange (with 10x-100x more nukes) would. I would personally be more worried about another global pandemic and/or biowarfare/bioterrorism. An infection with the virility of SARS-CoV-2 but the case fatality rate of Ebola or MERS would end civilization. What'll keep you up at night is realizing that this is almost at the point where a biology grad student could engineer such a thing in their dorm room. It should be noted that people who think about these things are also worried about AI existential risk. Personally I think that while there is reason to have some concern, it doesn't hold a candle to the above two risks.