Simple Global Carbon Model: The Atmospheric-Terrestrial Biosphere-Ocean Interface

Financial support provided by the Center for Global and Regional Environmental Research (CGRER) and NASA's Universities Space Research Association.

A simple global carbon model has been developed for scenario analysis, and research needs prioritization. CO2 fertilization and temperature effects are included in the terrestrial biosphere compartment, and the ocean compartment includes inorganic chemistry which, with ocean water circulation, enables the calculation of time-variable oceanic carbon uptake. Model-derived Q10 values (the increasing rate for every 10 degrees C increase of temperature) are 1.37 for land biota photosynthesis, 1.89 for land biota respiration, and 1.95 for soil respiration, and feedback temperature is set at 0.01 degrees C/ppm of CO2. These could be important parameters controlling the carbon cycle in potential global warming scenarios. Scenario analysis, together with sensitivity analysis of temperature feedback, suggests that if CO2 emissions from fossil combustion continue at the present increasing rate of ~1.5% per year, a CO2 doubling (to 560 ppm) will appear in the year 2060. Global warming would be responsible for 40 gigatons (Gt) as carbon (Gt C) accumulation in the land biota, 88 Gt C depletion from the soil carbon, a 7 Gt C accumulation in the oceans, and a 19 ppm increase in atmospheric CO2. The ocean buffering capacity to take up the execess CO2 will decrease with the increasing atmospheric CO2 concentration.