CO2 is a gaseous molecule. There is no difference between a CO2 molecule that comes from an automobile and one that comes from natural decay/oxidation.
I don't think it affects your basic point in terms of effects but they do say there is some difference between CO2 naturally generated by plants and that generated by burning fossil fuel. It's an "isotope" thing. See http://www.realclimate.org/index.php/ar ... s-updated/" onclick="window.open(this.href);return false; and go to the third paragraph to start reading about it.
I don't think they're saying it has different effects in terms of climate change though. Also I'm not even sure I buy what they're saying about being able to tell. I'd have to go take some Chemistry courses or something to find out.
JSO punks Tman..
The best way to keep people passive and obedient is to strictly limit the spectrum of opinion but allow very lively debate within that spectrum - Noam Chomsky
