The IPCC 4th assessment report shows 0.2 degrees Celcius per decade of warming for the last 30 years. I'm not going to argue this point, but we'll analyze it a tad.
If my math is correct in the previous post, that means we've had between a 6 and 9 ppm increase in CO2 due to burning fossil fuels, making concrete, etc, to go with a 0.6 degree C rise in average global temperature. When the IPCC says that the lower range of Carbon sensitivity is around 2.4 degrees (based on the lowest estimate of sensitivity) we should expect doubling carbon dioxide to raise the temperature 2.4 degrees. 2.4 degrees divided by 400ppm should give us a 0.006 increase in temperature per part per million of carbon. That means that atmospheric CO2 would need to increase at 33.3 ppm per decade to give a 0.2 degree celcius rise.
Does that sound a little outlandish? This is why the IPCC has to have such complicated feedback models involving water and other gasses, there just isn't enough man made CO2 in the atmosphere to account for the warming observed based against the anthropogenic carbon dioxide. The IPCC says that of that 2.4 degrees of sensitivity, somewhat around half of that is due to carbon and the rest is due to "positive feedbacks" in the climate models.
Now the craziest claim about CO2 in the IPCC assessment reports? Natural forces respond to anthropogenic carbon with yet even more carbon. But wait, didn't the IPCC also claim that natural forces took up 60% of anthropogenic carbon? Yes, yes they did. But if the world does get warmer, we know that atmospheric carbon dioxide will increase even without humans burning 29 gigatonnes of fossil fuels.
With high confidence I can say that a colder Earth has less carbon dioxide in the atmosphere, and a warm Earth has more carbon dioxide in the atmosphere. I cannot say with confidence that the current warming is caused by anthropogenic carbon dioxide based on observed CO2 measurements of our atmosphere since the end of the little ice age. The CO2 ppm swings have been on orders of magnitude beyond what we have put into the air.