...more rocks...

I would suggest [this title should be] "according to a number of studies" because there is more than one, referenced here -
http://www.ncdc.noaa.gov/paleo/globalwarming/paleolast.html .

I also think that the so-called "error bars" are not actually error bars but are 95% confidence intervals for a normal distribution curve. This makes a hell of a difference to their interpretation (and would explain why no one complains about them).

I think it all really boils down to risk management. What is the worst that will happen if CO2 emissions by humans are not having a negative effect (on the continued survival of the species) and we reduce Co2 emissions? We spend some more money than is necessary? One company with a lack of foresight (the most likely conspiracy here by a long chalk) makes less profit whilst other companies make more? Where is the science to say that decreasing CO2 in the atmosphere will have a detrimental effect? Even if CO2 naturally declines as after the Medieval Warm Epoch, last time there was no significant human influence apparently so we have no idea that it will happen this time. Even if decreasing CO2 in the atmosphere does have a detrimental effect, can't we just cut the price of fuel and give everyone SUVs to resolve the problem?

So, it boils down to (at least) the destruction of civilisation as we know it vs spending some money that we really don't have to vs an unproven detrimental lowering effect. Pass me my cheque book...