I think the question should be refined somewhat.
The globe warms and cools, no one contests that.
CO2 is a greenhouse gas and has a somewhat accepted direct response.
Human activity has caused the CO2 levels to increase, (% of increase from Human activity? unknown)
Perhaps the question should be,
Is the addition amplification of the direct response warming as defined by the IPCC occurring?
But this is not a believe question, but a data one.
If we go by Hanson's GISS data, we have warmed .8 C in the last 133 years.
The IPCC's direct response for CO2 number is 1.2 C for a doubling of CO2,
which means our current level of CO2 should produce .6 C of warming.
If there is any additional amplification from direct response increase,
it would have to be within the .2 C, of unaccounted for warming.
Let's see how the empirical data stacks up to the IPCC predictions.
The IPCC predicted the temperature increase from doubling CO2 levels
would be between 1.5 and 4.5 C.
At roughly half way through the effects of doubling CO2, we are at .8 C.
If we could complete the doubling, the observed data shows we would net out just under
1.6 C of warming over 200 years.
(NOTE: CO2 level at 401 ppm, results in 51% of the effects of doubling CO2)
4*log(560)-4*log(401)= .580, 1.2 C -.580 C= .62 C= 51.6%