Caldeira Lab Research:Energy, Global Carbon Cycle, and Climate

Multicentury Changes to the Global Climate and Carbon Cycle: Results from a Coupled Climate and Carbon Cycle Model

G. Bala, K. Caldeira, A. Mirin, & M. Wickett

Using a simulation made by a coupled climate and carbon cycle model, the possible effects of carbon emissions continued at estimated rates until 2300 are predicted. By the end of the model's run, a rise in temperature of 8K and an atmospheric CO2 concentration of 1423ppm were observed.

Bala, G., K. Caldeira, A. Mirin, M. Wickett and C. Delire, Multicentury changes to the global climate and carbon cycle: Results from a coupled climate and carbon cycle model. Journal of Climate 18 (21) 4531-4544, 2005.

Sharp rise in CO2 concentration and temperature: In the control simulation, human emissions were excluded from the data and no changes to CO2 concentration or temperature were observed. In the SRES A2 scenario, emissions data that has been predicted as probable to take place in the next few centuries was applied to the model, provoking a temperature increase of 8K and very high atmospheric carbon dioxide concentration.

Climate sensitivity on the rise: The model also predicted a rise in climate sensitivity, defined as the temperature change caused by a doubling of carbon dioxide in the atmosphere. Rising climate sensitivity provokes increased warming rates.


A coupled climate and carbon (CO2) cycle model is used to investigate the global climate and carbon cycle changes out to the year 2300 that would occur if CO2 emissions from all the currently estimated fossil fuel resources were released to the atmosphere. By the year 2300, the global climate warms by about 8 K and atmospheric CO2 reaches 1423 ppmv. The warming is higher than anticipated because the sensitivity to radiative forcing increases as the simulation progresses. In this simulation, the rate of emissions peaks at over 30 Pg C yr-1 early in the twenty-second century. Even at the year 2300, nearly 50% of cumulative emissions remain in the atmosphere. Both soils and living biomass are net carbon sinks throughout the simulation. Despite having relatively low climate sensitivity and strong carbon uptake by the land biosphere, these model projections suggest severe long-term consequences for global climate if all the fossil fuel carbon is ultimately released into the atmosphere.