[MrB]

Man's contribution to the greenhouse effect amounts to statisticaly noise:
Anthropogenic (man-made) Contribution to the "Greenhouse
Effect," expressed as % of Total (water vapor INCLUDED)

Based on concentrations (ppb) adjusted for heat retention characteristics	% of Greenhouse Effect	% Natural	% Man-made
Water vapor	95.000%	94.999%	0.001%
Carbon Dioxide (CO2)	3.618%	3.502%	0.117%
Methane (CH4)	0.360%	0.294%	0.066%
Nitrous Oxide (N2O)	0.950%	0.903%	0.047%
Misc. gases ( CFC's, etc.)	0.072%	0.025%	0.047%
Total	100.00%	99.72	0.28%

[Plutarch]

Wouldn’t we be able to tell how much C02 in the atmosphere is natural vs. man made based on the ratio of isotopes such as C14?