CO2 measurements from historical data (talking millions of years here) suggest we are at the lowest levels of CO2 in global history. Granted it is rising but we have a long way to go to even match the CO2 levels when the dinosaurs existed.
File:Phanerozoic Carbon Dioxide.png - Wikipedia, the free encyclopedia
As stated in the notes Ice ages have come and gone with significantly higher CO2 levels than we presently have and the scientist are at a loss as to the mechanisms which caused the global cooling. This all suggests that CO2 is not the direct cause of global temperature, larger factors are involved. There is another graph which plots Co2 levels vs past significant temperature changes and the data suggest CO2 lags the temperature variations suggesting it is not a causal factor but a symptom. There is some data suggesting global vegitation levels vs temperature which seem more credible than CO2 in explaining variations.
File:Co2-temperature-plot.svg - Wikipedia, the free encyclopedia
What caused the peaks and troughs over the last 800,000 years? Cycles of cave-man carbon tax?
I beleive global warming is and will happen and in the future it will reverse into global cooling. Man may have an significant input but he can not stop it happening, merely slow it down and by how much is very debatable.
In any case more problems for animal life have occured with global cooling than warming, ice ages have by far been the main conrtributor to mass extinction than any other cause.