[Bob434]

[[Where do you get that man is responsible for 3.4% of the .04% carbon in the atmosphere?]]

I can’t remember now, but here’s some info I found quickly

“Anthropogenic (man-made) CO2 additions comprise (11,880 / 370,484) or 3.207% of all greenhouse gas concentrations, (ignoring water vapor).”

http://www.geocraft.com/WVFossils/greenhouse_data.html

Note, this site lists ALL of the greenhouse gases, which figure out differently, but is still only 0.117% produced by man- if we are talking just CO2 produced by man, the figure comes out to just 0.00137& of the atmosphere

[palmer]

I looked through the page you linked to, then looked through the sources listed on that page. There is one that is quite incorrect: http://www.co2web.info. On that page they state "The stable 13C/12C carbon isotopes in the air's CO2 give us the only way to determine its anthropogenic fraction: ~4%".

There is absolutely no way to know that. There has been a very small drop in the 13C to 12C ratio thanks to fossil fuel burning. The drop corresponds to the fuel burning but cannot be used to determine how much fuel was burned or the percentage of manmade CO2 in the atmosphere. The percentage can be derived quite simply, there was 280ppm, now there is 400ppm. Natural rises in CO2 would have brought the 280ppm to about 285, maybe 290 at the most. The rest is manmade, so the manmade percentage is at least 25%.