Did those marbles hit you on the head and stun you? Follow the link down a page to where Motl calculates CO2 sensivity from the historical data:
Here is the general link, but his blog format doesn't allow my leading you exactly to the paragraph...you have to trudge down to it:
http://motls.blogspot.com/2009/04/birth-of-oil-geology-temperature-co2.html
Now, get ready for a shock. The result is14.854913 + 0.89326377 logCONC
This means that for 280 ppm, the predicted temperature should be 14.85 °C, higher than today. For 385 ppm, this function predicts 15.26 °C. The warming expected from a CO2 doubling, based on those 11 ancient historical points, is just 0.89 °C. Now, this result assumed that the whole relationship is due to the greenhouse effect. Actually, less then 10% is caused by the greenhouse effect.
This correction would imply that a sensible estimate for the climate sensitivity would be just a tenth of a degree
Now you want to talk about the cosmic ray issue? Lots of room left in there for other factors...