No climate scientist, that I know of, would dispute that CO2 concentrations appear to lag behind temperature in the paleoclimate data. In fact there are a bunch of papers about this lag, see
Caillon et al., 2003, Science magazine;
Lorius et al., 1990;
Monnin et al., 2001, Science Magazine
There appears to be about a 1000 year lag between the time that temperatures increase and an increase in CO2 concentrations during the 5000 year warming trends. What happens during the rest of those 4000 years? Unless you believe that CO2 has NO impact on our climate, in which case I can not help you, then the data suggests that the rising CO2 amplifies the warming trend until equilibrium sets in. According to the research the impact of this CO2 is about 1/3 of the total warming.
The fact that CO2 concentrations are rising in the atmosphere should not be in dispute. It has been known for a very long time that CO2 is a greenhouse gas and the data supports that conclusion. Humans are putting massive amounts of CO2 into the atmosphere, overwhelming the ability of the ocean and the biosphere to absorb the CO2, and we know the rise in CO2 is human caused because we have the isotope data to prove it. If you're interested in the literature you can check out these papers:
Stuiver, M., Burk, R. L. and Quay, P. D. 1984. 13C/12C ratios and the transfer of biospheric carbon to the atmosphere. J. Geophys. Res. 89, 11,731-11,748.
Francey, R.J., Allison, C.E., Etheridge, D.M., Trudinger, C.M., Enting, I.G., Leuenberger, M., Langenfelds, R.L., Michel, E., Steele, L.P., 1999. A 1000-year high precision record of d13Cin atmospheric CO2. Tellus 51B, 170—193.
Quay, P.D., B. Tilbrook, C.S. Wong. Oceanic uptake of fossil fuel CO2: carbon-13 evidence. Science 256 (1992), 74-79