On Apr 21, 9:45*am, "James" wrote:
[ . . . ]
I wonder what the percentage is. Co2 is miniscule and one of them has
been described as too heavy to enter the upper atmosphere.

But, if you get your information from real
scientists, instead of right wing witch
doctors, you get a much different story.
Please see:

http://www.esrl.noaa.gov/gmd/aggi/