Here you go...
http://scienceofdoom.com/2009/11/28/co2-an-insignificant-trace-gas-part-one/
This is probably the best explanation I have seen as to the greenhouse effect of CO2. The author presents his information clearly in common language without all the political snark found on most climate websites. He also covers many other areas of climate science so if you like what you see browse around a bit. I think his science is first rate.
My personal opinion for what it is worth:
Increased man made CO2 must cause increased warming at some level. Whether it will result in catastrophic consequences is a much more difficult question. I believe the sun has been underestimated in it's effect on climate change and if we get a quiet period (no sunspots over 50 years) the earth will cool and mask man made warming effects completely for a while. I classify myself as a lukewarmer.