I watched a show on Discovery where they speculated that the magnetic poles reversing were due to deep impact on the planet from asteroids or meteors. I think it'll be a rock that gets us, blacking out the sun and putting the planet into another ice age. Then, in 10 or 20,000 more years, new greenies will complain about global warming.....the earth reverses its magnetic poles about every three hundred thousand years, no big deal. just have to buy a new compass, or bust out a magic marker!