My understanding is the earth is due for a magnetic polar shift, one of those events that happen every 25,000 years. A couple of years back there was a report that the magnetic field is 20% weaker than 400 years ago, so maybe it's just starting. That would affect the cosmic rays/temperature if I'm not wrong.
I just went to check out info on polar shift and realized it feeds into that 2012 claptrap. I picked up my info from old tv science shows over the last decade, apart from shifting aurora's, I don't expect anything major if it happened in our lifetime.