I was watching something about this in Discovery Channel or something. Currently the greatest threat to us is the very thing that pretty much keeps us and just about almost every other being on this planet alive: The Sun.
You never know what the Sun can do, for one. It's highly unlikely that the Sun's fire will burn out during our lifetime, or during our children's children's lifetime, but it will happen. I've only heard that in 2012, there's going to be a solar flare that is going to be released from the sun. What this mean is that there's going to be a huge burst of heat energy from the sun and it'll be sort of like back-handing the earth(for lack of better description). The results from this would not have anything to do with our ozone layer as much as it would affect our magnetic field. Our magnetic field is what deflects just about most of the sun's rays and prevents our planet from overheating. Destroying that would result in Earth's cremation, pretty much.
So far, I've heard only that our magnetic field is getting weaker, and that it is unlikely that it will survive the solar flare attack from the Sun. When this happens, it will trigger a series of catastrophic events that would react in accordance to the solar flare. For one, a Super volcano could erupt(does anyone remember the one in Yellowstone park in Washington?). The eruption of a super volcano in the aforementioned area would spew up so much ash that it would cover Washignton, Part of California, Oregon, and honestly I think it would cover as much as the entire western half of the United States. Should the wind continue to blow this ash forthwith, then it could actually have the potential to blanket the entire United Stated for quite a while.
This is not the only occurrence, however.
The Supervolcano eruption would generate and shake up so much of the Earth's crust that it would cause a super tsunami afterwards, drowning out lands that are at least at sea level or not even that much above sea level. Going back to the U.S again, I believe that the central United States would be the only part of the U.S remaining after the Super Tsunami, since it flooded everything.
...I'm probably stretching things a bit far than what they really are, and I really have no specific stance on the matter personally. If it ends, then it ends. Complaining about it really won't change the date of the apocalypse now, would it? Remember, these are only things that I saw on Discovery channel, and it was pretty convincing for the most part, but I don't really choose to believe anything until the very day the actual world ends.
Just my two cents to the topic, though.
