>>14069677
I'm doing this on the fly, I'm not an expert, so I'm just going off of the information I can find through web searches.
Okay, first of all, there are over 4000 cities with a population of 100,000 people. If you were to take out each one of those cities, all nuclear powers just wasted a third of their arsenal. Now, using the pic in the cap I posted previous, a nuke would wipe out the city of San Fransico, which is 47 square miles (Just the city itself, not the entire country). If you were then to use all of the remaining nukes to wipe out just one location completely, 'congratulations, you have just enough power to obliterate Alaska (And nothing else).
To cap all of that off, you also have the numerous military bases and instillation across the globe. The first pic attached to this post is a diagram of all of the countries that have a known "U.S. military presence" as of 2015. On top of that, the U.S. has hundreds of bases world wide with there being a report of 500-800 in Middle East alone a few years back. Now, remember that is just the U.S. and no one else.
You also brought up areas like Yellowstone park. The kicker is that you cannot actually detonate that volcano above the ground. It would require a ridiculous large amount of nuclear devices to do so (Much more so than the amount that actually exist). You would have to drill through 8 km of rock and detonate the nuclear devices in one of the magma chambers (Which means it cannot work as part of a "sudden strike"). On top of that, while the blast "could" cause quite a bit of damage to the surrounding areas through the gases and ash the volcano spews out, Yellowstone isn't an "explosion waiting to happen". Apparently, the most amount of damage that would be caused is just bring lava to flow up and destroy the surrounding area. Nothing even close to the "apocalyptic event" people make it out to be.
>>14069791
Not a damn thing either. That is also one of the "Great myths" the media likes to use.
<Second pic
Long story short, we have VERY LITTLE to actually worry about.
Hell, I'd probably be more worried about that volcano on the West side of Africa going off (Because of it causing a landslide, that would create a tsunami, that would flood the entire U.S. East coast, and how it can all happen in a matter of hours) than I would worry about global warming and nuclear strikes.