Abstract

Abstract The paper examines terrestrial and oceanic carbon budgets from preindustrial time to present day in the version of Beijing Climate Center Climate System Model (BCC_CSM1.1) which is a global fully coupled climate‐carbon cycle model. Atmospheric CO 2 concentration is calculated from a prognostic equation taking into account global anthropogenic CO 2 emissions and the interactive CO 2 exchanges of land‐atmosphere and ocean‐atmosphere. When forced by prescribed historical emissions of CO 2 from combustion of fossil fuels and land use change, BCC_CSM1.1 can reproduce the trends of observed atmospheric CO 2 concentration and global surface air temperature from 1850 to 2005. Simulated interannual variability and long‐term trend of global carbon sources and sinks and their spatial patterns generally agree with other model estimates and observations, which shows the following: (1) Both land and ocean in the last century act as net carbon sinks. The ability of carbon uptake by land and ocean is enhanced at the end of last century. (2) Interannual variability of the global atmospheric CO 2 concentration is closely correlated with the El Niño‐Southern Oscillation cycle, in agreement with observations. (3) Interannual variation of the land‐to‐atmosphere net carbon flux is positively correlated with surface air temperature while negatively correlated with soil moisture over low and midlatitudes. The relative contribution of soil moisture to the interannual variation of land‐atmosphere CO 2 exchange is more important than that of air temperature over tropical regions, while surface air temperature is more important than soil moisture over other regions of the globe.