Two questions:
1. What evidence is available that indicates that CO2 concentrations increased prior to the receedance of the Wisconsin Ice Sheet instead of in response to changes in regional or global temperature increases?
2. How does the current atmospheric concentration of CO2 compare with the million year average CO2 concentration?
Just curious.
See post 167 for a full (though brief) explanation of glacial/interglacial variability.
How does the current atmospheric concentration of CO2 compare with the million year average CO2 concentration?
I can't reliably go back one million years. I can state authoritatively that the current CO2 concentration is about 80 ppm higher than at any time in the past 650,000 years. Prior to the Pliocene, atmosheric CO2 concentrations were higher. One data record I can check quickly indicates that CO2 concentrations have been roughly in the 180-280 ppm range for the Pliocene and Pleistocene, but that is an eyeball interpretation. See below.
Carbon and oxygen isotope record time-correlated with tectonic and climate events
