In the other thread we were discussing the hockeystick as valid proof for global warming due to anthropogenic increase in greenhouse gasses. However the purpose of that thread was more philosophycal, intended to identify the truly important. And it was centered around Rich Muller priceless remark: But we strayed to ice ages when as intermezzo, I showed a (old) carbon dioxide graph going back 600 million years with seemlingly little correlation between ice ages and carbon dioxide level in the atmosphere. So why don't we try and make our own 600 million years hockeystick, the relation between global temperatures and carbon dioxide. For starters I found a more recent carbon dioxide graph from the same author: http://calspace.ucsd.edu/virtualmuseum/climatechange2/07_1.shtml [Broken] and the http://www.studyworld.com/newsite/ReportEssay/Science/Earth\The_Ice_Age-36240.htm or rather global temperatures. Here is something: Also good ref: Pre Mesozoic Ice Ages John, C Crowell 1999 GSA ISBN 0-8137-1192-4 Note that the Ordovician – Silurian 440 Mya is about 18 times more CO2. The Devonian – Carboniferous border 350-360 million years (Mya) correspond with 3-4 times times the current carbon dioxide level while the Late Carboniferous - Early Permian era boundary, 290-286 Mya, is about level with nowadays. We also have the http://geog.hku.hk/undergrad/course/2038/2038cycl.htm [Broken] that shows the lack in correlation of CO2 especially in the 450 - 480 Mya time frame and a remarkable corrolation around the 300 Mya. On the other hand, between 200 - 100 Mya an inverted corrolation seems to exist with temps gradually rising and CO2 gradually lowering. But how accurate is all of this? Can we make a more accurate approximation and see how the Carbon dioxide - greenhouse correlation really looks like. There are however several more noise factors, the tectonics send the continents all around the globe. Formation of a big cluster of continents will affect global temperature, also when a sizeable continent passes the poles, a ice sheet will likely be formed, although one might wonder if that could happen with 18 times the current CO2 if the global warming idea was right. We also have no idea about the variability of the sun.