The latest Nicholas Cage movie called "The Knowing" I doubt any of you would be interested in seeing it. I thought it was rather lame. But long story short, earth gets blasted with a solar ray from the sun ripping the ozone layer from it and torching all life.
As long as we have our magnetosphere we should be fine.
Then again, if the Earth's core stops spinning, which creates the sphere, the entirety of Earth's surface would be scorched and turned into a desert. Part of the whole 2012 dealie is that the poles will shift, and some speculate this will weaken the magnetosphere for a time (something like that).