I'm not denying it, just the degree to which it affects the climate. There are other factors, such as solar high-energy activity (I'm not talking about solar irradiation) that are quite possibly/probably more significant and that also explain the variations in global temperatures over previous centuries.
http://hockeyschtick.blogspot.co.uk/2013/04/new-paper-demonstrates-temperature.html
Some discussion here:
http://www.skepticalscience.com/co2-lags-temperature.htm