1  The irony of this is that there will be another ice age. Its in earths future. Imagine what would happen if another Yellowstone event where to happen anywhere along the Mississippi river fault and was so large that it split the US in two. This could happen along any of earths fault lines. The result of such a cataclysmic event would be no sun for decades. Or we could be hit by an asteroid, say in Russia, lots of dust thrown into the atmosphere and instant ice age. To take to the extreme what if for a cosmic reason our sun halved its solar energy output. Thats total Ice Age for this planet.

2 Amen Mike!

In 536 a series of volcanic eruptions pretty much blotted out the sky all over the western world. It was horrendous in Ireland, where the peaceful  and prosperous civilization of the time fell completely due to two whole years of near complete darkness (there is no tree ring growth for those two years anywhere on the Islands.) The rest of Europe suffered from dimming of the sun and what is now called the volcanic winter by scientists. Imagine if that happens again!

And essentially these idiots who want to geoengineer to "solve" co2 driven warming (something still not proven) could well trigger another such volcanic winter. There is a reason why Europe exoperienced the Dark Ages immediately after this climate event. It wrecked agriculture in the whole of the western world.

Your other examples are entirely possible too and have happened in days gone by. Our fault line at New Madrid here in Missouri, for instance, has been giving off a lot of tremors of late - many more than we've had in a long time - and it could blow. The worst earthquake in the Continental U.S. was the 1811 New Madric quake, which turned the Mississippi river backwards for weeks.

There are a lot of things that could happen and that these folks could worry about. A fraction of one degree of atmospheric warming isn't one of them.