Cogitator,
Be sure to double-check Richard Alley’s assertions.
What are the CO2 estimates over the past 25 million years? (180 ppm to 380 ppm) What are the temperature estimates? (-5.0C to +4.0C) The doubling estimates do not work at this time scale nor any timescale in the historical climate.
Of course, Richard Alley never showed the math in that presentation. He just told you it is almost nailed.
I'm breaking silence because I don't know where you got your CO2 (atmospheric concentration) estimates. The first paper's pretty easy to read on this.
Linkages between CO2, climate, and evolution in deep time (PDF)
Marked Decline in Atmospheric Carbon Dioxide Concentrations During the Paleogene (abstract only)