With respect to the precise data and trends, I think I've said before that I would have to do far more thorough research to hold a debate with you on that. On the face of it I think you are making a mistake in interpreting the results because you seem to be seeking a linear trend -- so much C02 in gives such-and-such a temperature rise -- but I don't see why you should expect this to be the case. It's pretty much never true anywhere else, and particularly so in an uncontrollable experiment, which is what the Earth basically is. There are evidently going to be other factors in play that can negate the change due to C02, or shroud it, or act as distractions somehow. The idea that T = A x C for some constant A and some amount of Carbon C in the atmosphere is one that needs to be discarded rather rapidly if you are going to have any kind of sensible debate about this topic, and it seems to me that this sort of idea is floating around in the subtext of your posts on this topic.
That aside, however, what is beyond doubt is that C02 is a greenhouse gas, ie that it absorbs/ emits IR radiation, and so it certainly can have an impact on the temperature of the Earth. One need only look at Venus to see that. What TTT, andy-hughes and NJ appear to be saying is that, absent certainty, we should do nothing about the potential risk. This position is based on ... well, I'm not sure really. It seems to me that Andy is saying that we should have waited until HIV had reached pandemic proportions before trying to counter it, or (NJ) until CFC levels had destroyed the entirety of the ozone layer before caring. Equivalently, perhaps we should wait for the next 100-200 years to see if unsustainable human activity that is destroying long-term natural cycles and wrecking entire ecosystems is going to go un-noticed?
It may very well be the case, after all, that CO2 levels can rise indefinitely with minimal impact on the environment. But I doubt it. There is always the potential for reaching some nasty "tipping point", where, say, the levels directly contributed to only a small rise in temperatures, but this was enough to trigger more significant impact factors, such as locked-away stores in permafrost. It may even be the case that this is already unavoidable, and for that matter through no fault of our own. But, again, I doubt it. It's clear that human activity has had and will continue to have effects on the planet. How large or small those effects will end up being is not nearly so relevant as the fact that they *might* be large, and it seems better to try and avoid that risk if at all possible.
Switching away from a reliance on fossil fuels makes some pragmatic sense anyway, since there is obviously a finite supply (also politics), so we'd have to switch at some point (oddly, this point always seems to be 40 years away or so -- but it will come eventually).
In the long run, it's better to overstate the risk, take action, and never see the full potential for devastation actually occur, than it is to sit back and wait to see if those damned scientists with their crazy visions of apocalypse were right after all.