ABSTRACTA two-dimensional inversion calculation is used to estimate the distribution of surface sources of atmospheric CO2 in space and time. These estimates are then modified to account for the role of CO and CH4 in the atmospheric carbon budget. The results confirm previous estimates of a weak (oceanic) sink in the southern hemisphere of 1.3 Gt C yr−1 and a northern sink of 1.9 Gt C year−1. These sink strengths are disproportionate to the ocean areas although, compared to our previous studies, the CO correction has reduced the degree of disproportion. Because of a number of near cancellations, the CO correction leads to little change in the net carbon budget of the tropics. Combining the net release estimate for the region 12°S to 12°N with independent estimates of oceanic CO2 release implies that, in this region, the terrestrial biomass is nearly constant or even slowly increasing, in spite of massive deforestation. The implications for the global carbon budget are discussed.