One simple term...........MEDIEVAL WARMING PERIOD..........done.
http://dailycaller.com/2013/12/13/study-earth-was-warmer-in-roman-medieval-times/
The climate crusaders never want you to know about it!! No SUV's rolling around the planet = lose.
The MWP and LIA certainly do show that CO2 is not the main control knob for climate. Natural factors rule (but CO2 still has a bit part).
I don't even think it's effect is measurable. I think that the GHG effect of water vapor is so overwhelming that the CO2 signal is for all intents, invisible.
I concur that H2O is the dominant greenhouse gas.
But CO2'S effect is not invisible, especially if you consider the total effect not just the effect of rising CO2.
If CO2 was not present the the atmospheric window would be widened, allowing more radiation to escape freely to space, and would cool the atmosphere by removing one of its sources of energy input.
And here I disagree with you. It is invisible. Were there no water vapor its effect would be measurable. However, as we all know, water vapor is the dominant GHG and it simply obliterates whatever effect CO2 would have absent the water vapor. The effect from the CO2 is so miniscule as to be completely immeasurable. We see this in the raw data that we do have access to. No matter how much the CO2 level has increased, the net result has been zero.
We see this in the paleoclmate record as well.