The earth's magnetic field moves around quite a bit, and every so often the polarity switches so that magnetic north becomes south and vice verse. It's looking like we are approaching one of these shifts, and scientists really don't know what effects this will have on the earth.
So, before researching this more, I have a hypothesis. I think that the shift will cause a shift in seasons. It's already happening. I don't think all the climate changes we're having could be attributed to global warming alone.
In our current polarity, the northern hemisphere has summer May-September ish and at that same time the southern hemisphere is having winter. October-April it's winter in the northern hemisphere and summer in the south. So the magnetic shift will cause this to flip-flop. I feel this has been pretty obvious over the last several years as winter starts later and later and so does summer. Last year I had a botany class from May to June. The topic was flowering plants of Utah and we went on a field trip every week. Even though it was May, we had a very hard time even finding any plants that were flowering at that point because spring was so late. We even had it snow on one of our field trips. Last month (December 2011) we had record high temperatures and low precipitation, and January has been much the same. I've heard some people express worry of a drought because of this, but I don't think that will be an issue, it's just a matter of the seasons being delayed. So I think this trend correlates with the heightened activity of magnetic shift that's been happening, and both changes will continue until the polarities and the seasons of the hemispheres have swapped.
I'll go research it more and find out if my hypothesis has any possibility of being true or if someone has already established or debunked the same idea.