For some compelling data to back up Chuck's statements take a look at this article: Science 25 November 2005: Vol. 310. no. 5752, pp. 1313 - 1317 Stable Carbon Cycle–Climate Relationship During the Late Pleistocene Urs Siegenthaler,1 Thomas F. Stocker,1* Eric Monnin,1 Dieter Lüthi,1 Jakob Schwander,1 Bernhard Stauffer,1 Dominique Raynaud,2 Jean-Marc Barnola,2 Hubertus Fischer,3 Valérie Masson-Delmotte,4 Jean Jouzel4 A record of atmospheric carbon dioxide (CO2) concentrations measured on the EPICA (European Project for Ice Coring in Antarctica) Dome Concordia ice core extends the Vostok CO2 record back to 650,000 years before the present (yr B.P.). Before 430,000 yr B.P., partial pressure of atmospheric CO2 lies within the range of 260 and 180 parts per million by volume. This range is almost 30% smaller than that of the last four glacial cycles; however, the apparent sensitivity between deuterium and CO2 remains stable throughout the six glacial cycles, suggesting that the relationship between CO2 and Antarctic climate remained rather constant over this interval. In other words, the increased CO2 levels we are recording today (with resultant increase in average global temperatures) are not part of some "normal" cycle.