Earth's Carbon Resources
Moore, et al. report a mass of about 7 x 1011 tons of carbon in the atmosphere as CO2 and about 4.5 x 1011 tons of carbon in vegetation as carbohydrate. The nominal percentage of CO2 in the atmosphere is about 0.034 percent although in recent years this percentage has been increasing and a reported figure for 2004 is about 0.038%.
From a table on the abundances of the elements in living organisms, carbon is listed at 18.5% of the human body compared to about 0.03% of the Earth.
Moore, et al.