Tony2046, some have pointed out that Climate Change such as Ice Ages have come and gone without human intervention. That is true, and the cycle of Ice Ages appears to correlate with small changes in the Earth's orbital elements (orbital eccentricity, orbital tilt, etc.), as described at:
http://geography.about.com/od/learnabouttheearth/a/milankovitch.htm
Evidence that appeared to prove this theory was published in: Hays, J.D. John Imbrie, and N.J. Shackleton. "Variations in the Earth's Orbit: Pacemaker of the Ice Ages."
Science. Volume 194, Number 4270 (1976). 1121-1132. I am not an expert in the field (I specialize in laser physics), but I did my M.S. work in this area at the National Center for Atmospheric Research (then in Boulder, CO). So, I am not an expert, but I know more than the typical person staying at Holiday Express.
The upshot is: the Earth's cycle of Ice Ages appears to correlate with small changes in the Earth's orbital elements. How these very, very small changes in the Earth's orbit result in driving the Earth's Ice Age Cycle is not really well understood, evidently very small changes in solar flux and distribution of solar flux over a very long time causes gigantic changes in the Earth's climate (Ice Ages).
As you point out Tony2046, humans are making what would appear to be much more profound changes in the environment by the big increase in atmospheric CO2 and other greenhouse gases due to burning of fossil fuels. These greenhouse gases are largely transparent to "incoming" light from the sun, but they strongly absorb the Earth's "outgoing" re-radiation in the infrared which tends to "trap" this infrared re-radiation (the Greenhouse effect, why your car gets hot in summer, and why Venus is so hot). Theoretically, this would cause global warming from a simplistic point of view.
Thus, Climate Experts fear that the Earth is experiencing global warming due to the emission of these greenhouse gasses. Current supercomputer climate models predict a 2-3 degree Celsius warming by 2050.
However, the Earth's climate is really, really complicated, and not very well understood, that is why there is so much confusion and argument on this issue. The computer models could be right (2-3 degrees warming by 2050), or it could be not that bad (or even negligible), or even worse than predicted. Really, we don't know for sure, the Earth's Climate is too complicated.
However, back to your original point, if the small changes in the Earth's orbital elements drove the Ice Age cycle (admittedly over very long time scales), what are we doing by putting so much CO2 in the atmosphere? Nobody really knows, but in the opinion of almost all Climate Scientists (and IMHO also) we are playing with fire.