This is not a thread for Doomers

[Jgarrick]

19. All right...let's look at each of these scenarios one by one:

A very large asteroid smacks the earth.

Well, that depends on one's definition of "large", doesn't it? If an asteroid with a diameter of about a mile hit the earth, it would be civilization-wreaker. It would probably land in one of the oceans...which is bad. We're talking thousand-foot high tidal waves impacting the world's coastal cities and a nuclear winter. Some civilization would probably survive, but it would knock us back a century or ten. If the asteroid is smaller, the effects would be smaller as well. Of course, if it's much bigger (say, 7 to 10 miles wide, like the one that wiped out the dinosaurs) you can kiss humanity goodbye. Make it 50 miles wide and you can say goodbye to anything above the level of a cockroach.

The good news is that there's virtually no chance of an asteroid even 1 mile wide hitting us for the forseeable future. Any asteroids of that size (and considerably smaller) has been discovered and its orbit mapped out.

Of course, there's the chance that a comet from the Oort Cloud could come out of nowhere and slam into us, which much the same results...but the chance of that happening anytime soon is extraordinarily small.

Global warming leads to acidic oceans, 10 foot higher sea levels and a greatly altered climate right in your back yard.

Even were such a worst-case scenario to come to pass, it
a) Isn't likely in your lifetime.
b) Wouldn't result in civilization being wiped out, although it would have a drastic impact on it.

Radiation from the 430+ nuclear power plants is, one way or another, unleashed much the same as Chernobyl, or Fukushima.

What...all at once? We've had 2 such events in half a century. Even were the rate of such disasters to increase by a factor dramatically, it wouldn't be a civilization-wrecker. Mind you, from a personal perspective I wouldn't want to be downwind of one.

A sun spot releases a Coronal Mass Ejection that ends up directly hitting earth and thereby burning up our electric grid.

Now this one could be a civilization-wrecker. Were such an event to occur (and one did 1859!) it could destroy the entire power grid, resulting in hundreds of millions, perhaps billions of deaths. It's estimated that a coronal mass ejection of such magnitude occures every 500 years or so. Isn't that a cheery thought?