| CO2 sources | Flux (Gt C/yr) | |
| Respiration | ||
| Decomposition | ||
| Combustion | ||
| total = 60 | ||
| CO2 sinks | ||
| Photosynthesis | 60 | |
| Source: Climate Change 1995, published by the IPCC | ||
Residence time is
defined as the size of the reservoir divided by the rate of inflow or outflow.
As the total reservoir of CO2 is 760 Gt and the outflow is 60
Gt per year, the residence time is 12.7 years.