This article covers a couple billion years or so of Earth history in regard to the relationship of CO2 and temperature. What is truly amazing is that the temperature has had a wide range, but has never gotten so high as to boil away our water supply. Further the temperature has stayed in a range that would allow life and evolution to continue on a course to what we see now. There is a close relationship between CO2 and temperature but many other modifying factors are discussed.-http://www.newscientist.com/article/mg20627661.200-climate-control-is-co2-really-in-charge.html