Effects of increased CO₂ in Earth's Past

Tim Patterson is a paleoclimatologist and Professor of Geology at Carleton University in Canada. He appeared before the Commons Committee on Environment and Sustainable Development in 2005 and testified: "There is no meaningful correlation between CO2 levels and Earth's temperature over this [geologic] time frame. In fact, when CO2 levels were over ten times higher than they are now, about 450 million years ago, the planet was in the depths of the absolute coldest period in the last half billion years. On the basis of this evidence, how could anyone still believe that the recent relatively small increase in CO2 levels would be the major cause of the past century's modest warming?"