An astrophysical explaination of the periodicity of ice age is offered today:
astro-ph/0209252
Title: The Spiral Structure of the Milky Way, Cosmic Rays, and Ice Age
Epochs on Earth
Authors: Nir J. Shaviv
Comments: 33 pages, 11 figures. To Appear in New Astronomy
The short term variability of the Galactic cosmic ray flux (CRF) reaching
Earth has been previously
associated with variations in the global low altitude cloud cover.
This CRF variability arises from changes in the solar
