Two adjacent 50 year periods are compared side by side, for overall global temperature rise, and overall ambient CO2 rise:
1912 to 1961: the temperature increase is 0.52C, the CO2 increase, 18ppm.
1962 to 2011: the temperature increase is 0.41C, the CO2 increase, 74ppm.
Whatever the overall effect of the CO2 increase is on global temperature, it is clearly not a dominating factor causing warming. The atmosphere is behaving as if the extra CO2 does not really matter very much at all since the temperature jumps are similar, whilst the CO2 jumps are clearly not.
(Edited 22 Jan 2012 to delete last two sentences in the original Note for being inessential)