Well my friend, while the Earth exchanges a great deal of carbon between the ocean, atmosphere, soil, and biosphere, it is the net balance which is of greatest concern to us. Without human influence, this regulatory process produces a net carbon increase of 0.0 Gt/year. During 1850-2000, through a combination of fossil fuel burning, cement manufacturing, and land-use changes, humans added a net 174 Gt of carbon. This caused the majority of an increase from 288 ppm (parts per million) to 369.5 ppm of CO2. As mentioned above, we currently add 8 Gt/year to the atmosphere.
