[ashleyn]

Nuclear war.

This may sound positively retro and cold-warish, but IMO we've had way too many close calls in the 80 years nuclear weapons existed, and the quality of governance worldwide only seems to decline.

Neither the United States nor the Soviet Union treated each other with the vitriol that Russia and the US do today. Do you believe Putin and Trump are half the gentlemen Kennedy and Khrushchev were? I seriously believe we are closer now to nuclear deployment than at any time after 1945. During the Cuban Missile Crisis, Khrushchev was dreadfully worried about nuclear war and wrote many cables to Kennedy sorrowfully bemoaning the thought. While today, Putin airs propaganda to an increasingly uneducated audience treating a theoretical first nuclear use as unremarkable, and his ministers seem more concerned with the idea of whether or not they can ever beat MAD.[1] Trump liked to brag about the size of his "button" to Kim Jong Un like it was a WWE script. There's little hope I have that the world will escape, even a limited tactical deployment in the coming two decades, playing fiery chicken with the future of humanity.

[1]: https://www.bbc.com/news/world-europe-65119595

[violet13]

Nuclear war is not an extinction event, though. Most people would survive, and while they would face hardships, the "radioactive wasteland" thing is a fairly sloppy sci-fi trope.

[twojacobtwo]

OP didn't say extinction event.

That aside, if all nukes were launched, it's not about the directly irradiated areas. Imagine how much fallout will be launched into the upper atmosphere when 10,000+ nukes hit, with many in the multi-megaton range.

The sheer amount of material thrown into the air could virtually blot out the sun for potentially years. Given that a large portion will be radioactive, it could be raining death for years too.

[wdh505]

Ehh the dust will fall out of the atmosphere within a few months. Large population centers will be craters proba ly. The 4 year nuclear winter will cause starvation and eating the "long pork" such that up to 90% of the population globally will die.