From the beginning of time on the Earth there have been cycles of ice ages and warming. I wonder how much we can blame on Fred Flintstone, he never used bio-fuel in his Rockmobile and he never used any type of filter over his rockpit stove to keep the air smoke free. I think I remember a science teacher telling me that the Earth is a wobbling mass spinning on its axis as it revolves around the Sun. The wobbling and spinning causes it to tilt to and fro hence warming and cooling. Al Gore is sick.