How about a massive computer shutdown, brought on by a virus attack that fulfills all the empty promises of Y2K?
Power grids shut down, missiles fire by themselves, thousands stuck in elevators, malfunctioning traffic lights kill millions... that sort of thing.
Or how about a massive solar flare? It could do all that, burn out power plants planetwide, and maybe knock a few (plutonium-fueled) satellites out of orbit. If it ejects a lot of charged particles and they stick around (have no idea how valid this is, but still...) most electric stuff won't work anymore. Cancer skyrockets as survivors try to forge a world without electricity - no computers, no phones, no lights at night, no cars....
One of my favorites has been ice-9. Kurt Vonnegut, Cat's Cradle: a research chemist creates a form of water crystal that's more stable than normal ice. It won't melt at room temperature. And it acts as a seed crystal for ordinary water. You swallow a flake of ice-9, and your body freezes solid. One speck of ice-9 hits the ocean, and that's it. No more ecosystem.
Oh, and you left off the old ice age/global warming thing. Either we all freeze, or we all drown in melted glaciers & get melanoma. |