Do you know of historical data on the web for global coal and petroleum consumption for the last few hundred years? It'd be very interesting to correlate it with CO2 concentrations.
Annual Global Per-Capita emissions of anthropogenic CO2 have risen to an apparent production/transport limited value of 1.14 ± 0.021 metric tons carbon per per person.
Source: Marland et al. (2006), CDIAC, Oak Ridge National Laboratory
This is especially interesting in light of project world population trends where population growth is becoming linear as opposed to exponential.
and the fact that surface temperature dependance on the absorption of thermal infrared by CO2 is proportional to the 4th root of the logarithm of CO2 concentration.
To put it all in simple terms, incremental temperature increase due to changing CO2 decreases with atmospheric concentration. The potential effectiveness of CO2 as a driver of climate decreases with its concentration in the atmosphere.
In point of fact the direct radiative effect of CO2 on surface temperature is on the order of 0.2oC for each doubling in concentration due to these factors.