Global Carbon Cycle Under the IPCC Emissions Scenarios
Increasing carbon dioxide emissions from fossil fuel use and land-use change has been perturbing the balanced global carbon cycle and changing the carbon distribution among the atmosphere, the terrestrial biosphere, the soil, and the ocean. SGCM(Simple Global Carbon Model) was used to simulate global carbon cycle for the IPCC emissions scenarios, which was six future carbon dioxide emissions from fossil fuel use and land-use change set by IPCC(Intergovernmental Panel on Climate Change). Atmospheric CO2 concentrations for four scenarios were simulated to continuously increase to 600~1050ppm by the year 2100, while those for the other two scenarios to stabilize at 400~600ppm. The characteristics of these two CO2-stabilized scenarios are to suppress emissions below 12~13 Gt C/yr by the year 2050 and then to decrease emissions up to 5 Gt C/yr by the year 2100, which is lower than the current emissions of 6.3±0.4 Gt C/yr. The amount of carbon in the atmosphere was simulated to continuously increase for four scenarios, while to increase by the year 2050~2070 and then decrease by the year 2100 for the other two scenarios which were CO2-stabilized scenarios. Even though the six emission scenarios showed different simulation results, overall patterns were such similar that the amount of carbon was in the terrestrial biosphere to decrease first several decades and then increase, while in the soil and the ocean to continuously increase. The ratio of carbon partitioning to the atmosphere for the accumulated total emissions was higher for the emission scenario having higher atmospheric CO2, however that was decreasing as time elapsed. The terrestrial biosphere and the soil showed reverse pattern to the atmosphere.