The figure below portrays estimated sizes of the earth's carbon reservoirs, average annual changes in the amount of carbon held in the reservoirs, and recent flows of CO2 between land and ocean reservoirs and the atmosphere. The size of carbon reservoirs are written in white, while natural processes between these reservoirs appear in yellow. Additional carbon introduced into the system by humans appears in red. For example, humans release 9 GtC/y but 3GtC/y are taken up by plants and soil carbon and another 2 GtC/y goes into the ocean. The remaining 4GtC/y goes into the atmosphere, increasing CO2 concentrations.
|Note: Tan colored pool is decreasing in size. Blue colored pools are increasing. Intensity of blue indicates magnitude of stock change. Numbers in red indicate estimated total amount of carbon in reservoir. Numbers in green indicate average annual change in amount of carbon in reservoir.|
Gigatons (Gt) = 109 metric tons.
Sources: Bolin et al. in IPCC, 2000a; Houghton, 1997.