Considering the natural level of CO2 in the atmosphere has gyrated hugely just what is the 'appropriate' level we're aiming for?
The issue with the 'science' is that the measures of historical CO2 levels are not accurate. The warmests use ice core data to determine what the historical CO2 concentrations were. The problem with this method is that CO2 is soluble in water, the colder the water the more soluble it is. CO2 is also 70x more soluble than nitrogen and 30x more soluble than oxygen.
This means that, when an air bubble is trapped in ice, not only does the liquid in the ice continue to absorb gasses, it does so SELECTIVELY, favoring carbon dioxide, by a huge margin, over the other common gasses in the air bubble. Is it any surprise then that the ice core data shows historically low levels of CO2?
Other proxy data show much greater variations over time than does the ice core data.
There are theories that the gigantism of the dinosaurs is directly related to the elevated CO2 levels and it's effect on providing the plant growth required to sustain such large creatures.
