Reply #2: On top of everything else, we now need to worry about a

[lapfog_1]

magnetic pole "flip". They happen every so often. No one knows quite why. The environmental effects could be devastating.

Or maybe not.

"Because the magnetic field has never been observed to reverse by humans with instrumentation, and the mechanism of field generation is not well understood, it is difficult to say what the characteristics of the magnetic field might be leading up to such a reversal. Some speculate that a greatly diminished magnetic field during a reversal period will expose the surface of the earth to a substantial and potentially damaging increase in cosmic radiation."

http://en.wikipedia.org/wiki/Geomagnetic_reversal