Check out http://www.freerepublic.com/focus/f-news/1670875/posts#21 and the links to Muller's website. Also check out this video., http://muller.lbl.gov/images/inner.mov, which shows eccentricities in the earth's orbit over the last 3 million years. It's a 12 MB file, so click at your own risk.
--I don't doubt that warming and cooling occur--just suspect that sun variation and earthly things-vulcanism, meteor impacts, etc., -make the most changes---