Global Warming and our Changing World

I saw a short segment on television within the past 24 hours detailing how the Mayan civilization existed during a time when the sun's solar output diminished for some reason. This caused a global cooling trend, which shifted ocean currents, and dried out the Mayan territory. Major droughts eventually lead to cultural devastation.

So now, with our man-made greenhouse gases, will we create a global warming trend that shifts ocean currents and causes major freezing in the northern hemisphere? The show displayed what might happen - video of a super blizzard wiping out cities.