Endlich of News New Mexico:
I asked Hansen about two periods in geologic history. First was end of the Ordovician, about 450 million years ago when CO2 increased from 4000 to 4400 PPM but earth entered a “snowball earth” phase. Second was the end of the Jurassic 150 million years ago, when CO2 was increasing, but temperatures fell. He told me that the data were wrong.
I specifically asked him about the measurements which showed large amounts of CO2 during the Cambrian and Ordovician about 4000-6000 PPM, and that even the IPCC speaks of large amounts of CO2 in the early Paleozoic. He said that there were no measurements of large CO2 amounts in the Paleozoic and again said I was wrong. I guess he has not heard of the Royer Compilation
I then asked about the Vostok Ice Core data which shows four previous interglacial periods CO2 was about 200-270 PPM, and temperatures were clearly much warmer that the present. “Dr Hansen, doesn’t the fact that the previous interglacials were a lot warmer than now, falsify the claim that CO2 is an important driver of climate?” He argued with me that the Vostok Ice core data did not show this, and said I was wrong. Google http://en.wikipedia.org/wiki/File:Vostok-ice-core-petit.png to see the data yourself.