Observational Contrains on the Global Atmospheric Co 2 Budget

Observed atmospheric concentrations of CO 2 and data on the partial pressures of CO 2 in surface ocean waters are combined to identify globally significant sources and sinks of CO 2 . The atmospheric data are compared with boundary layer concentrations calculated with the transport fields generated by a general circulation model (GCM) for specified source-sink distributions. In the model the observed north-south atmospheric concentration gradient can be maintained only if sinks for CO 2 are greater in the Northern than in the Southern Hemisphere. The observed differences between the partial pressure of CO 2 in the surface waters of the Northern Hemisphere and the atmosphere are too small for the oceans to be the major sink of fossil fuel CO 2 . Therefore, a large amount of the CO 2 is apparently absorbed on the continents by terrestrial ecosystems.