During my extensive (ongoing) research on the subject, I concluded on the following:
A. The Long Count of the Mayan Calendar, which ends on Dec. 21 2012, counts a cycle of approx. 26.000 years. This cycle is also known as the Precession of Equinoxes or a Platonic Year.
B. According to the british geologist James Lovelock (Ages of Gaia), every 26.000 years the Earth's position shifts slightly and receives more Sun radiation. Every third period of this cycle (75.000 years) the Earth has been in an Ice Age. The latest Ice Age was indeed 75.000 years ago and it was caused by the erruption of the Indonesian supervolcano Toba.
The problem is that during the 1700's and early 1800's we were heading for another Ice Age, but the Industrial Revolution not only stopped the trend, but it actually reversed it. The Earth is getting closer to the Sun, but instead of being frozen during the process, it's overheating.