I really hate getting pulled into discussions about this kind of crap, because there's almost always more opinion than reason involved, but...
Here's a little table I pulled off Wikipedia - it may be off in minutiae, but pretty much agrees with everything I've read:
Composition of dry atmosphere, by volume ppmv: parts per million by volume
Nitrogen (N2) 780,840 ppmv (78.084%)
Oxygen (O2) 209,460 ppmv (20.946%)
Argon (Ar) 9,340 ppmv (0.9340%)
Carbon dioxide (CO2) 387 ppmv (0.0387%)
Neon (Ne) 18.18 ppmv (0.001818%)
Helium (He) 5.24 ppmv (0.000524%)
Methane (CH4) 1.79 ppmv (0.000179%)
Krypton (Kr) 1.14 ppmv (0.000114%)
Hydrogen (H2) 0.55 ppmv (0.000055%)
Nitrous oxide (N2O) 0.3 ppmv (0.00003%)
Xenon (Xe) 0.09 ppmv (9x10−6%)
Ozone (O3) 0.0 to 0.07 ppmv (0% to 7x10−6%)
Nitrogen dioxide (NO2) 0.02 ppmv (2x10−6%)
Iodine (I) 0.01 ppmv (1x10−6%)
Carbon monoxide (CO) 0.1 ppmv
Ammonia (NH3) trace
Not included in above dry atmosphere:
Water vapor (H2O) ~0.40% over full atmosphere, typically 1%-4% at surface
You will notice that CO2, the major culprit in global warming, comprises a whopping .0387 % by volume of the atmosphere.
My undergrad degree was a dual in Biology and Chemistry, and I was forced to learn about CO2 cycles over the eons and ecological effects involving Ice Ages and warm cycles and........it's all WAY tedious to try to recall. I do recall that coring samples from Antarctica demonstrate natural hot and cold cycles in the overall planetary climate predating mammals in general, man in particular. These were all accompanied by atmospheric CO2 increases and decreases, thought to be triggered by changes in the gas's solubility in ocean water due to water temperature changes.
There's a weird self-flagellating portion of my personality that wants to feel guilty because I'm a profligate CO2 producer and by not fixing it I'm helping to consign mankind to the fate of the Pterodactyl. But then I come to my senses.
I've left science way in my past, but CO2 is less than 4 hundredths of 1 percent of the atmosphere NOW, when we're all in deep **** over global warming because of the stuff. Has anybody ever posited what a GOOD proportion of CO2 is?
I feel a sudden need to release a little CO2 - via 22 oz of Newcastle Brown Ale. Thinking about this **** makes me thirsty. And tired.