Approximately 250,000 measurements made for the pCO 2 difference between surface water and the marine atmosphere, ⌬pCO 2 , have been assembled for the global oceans. Observations made in the equatorial Pacific during El Nino events have been excluded from the data set. These observations are mapped on the global 4°؋ 5°grid for a single virtual calendar year (chosen arbitrarily to be 1990) representing a non-El Nino year. Monthly global distributions of ⌬pCO 2 have been constructed using an interpolation method based on a lateral advection-diffusion transport equation. The net f lux of CO 2 across the sea surface has been computed using ⌬pCO 2 distributions and CO 2 gas transfer coefficients across sea surface. The annual net uptake f lux of CO 2 by the global oceans thus estimated ranges from 0.60 to 1.34 GtC⅐yr ؊1 depending on different formulations used for wind speed dependence on the gas transfer coefficient. These estimates are subject to an error of up to 75% resulting from the numerical interpolation method used to estimate the distribution of ⌬pCO 2 over the global oceans. Temperate and polar oceans of the both hemispheres are the major sinks for atmospheric CO 2 , whereas the equatorial oceans are the major sources for CO 2 . The Atlantic Ocean is the most important CO 2 sink, providing about 60% of the global ocean uptake, while the Pacific Ocean is neutral because of its equatorial source f lux being balanced by the sink f lux of the temperate oceans. The Indian and Southern Oceans take up about 20% each.Measurements of the atmospheric CO 2 concentration indicate that it has been increasing at a rate about 50% of that which is expected from all industrial CO 2 emissions. The oceans have been considered to be a major sink for CO 2 . Hence the improved knowledge of the net transport flux across the air-sea interface is important for understanding the fate of this important greenhouse gas emitted into the earth's atmosphere (1-5).A number of different approaches has been used for estimating the role of the oceans as a CO 2 sink, yielding a wide range of estimates for the CO 2 uptake flux (3). Most commonly used are ocean-atmosphere CO 2 cycle models. In these models, ocean circulation is modeled using various schemes ranging from one-dimensional box-diffusion models (4, 5) to threedimensional ocean general circulation models (6-8), and biological processes are assumed to be invariant with time and are not explicitly described. These ''perturbation'' models yield an oceanic uptake of about 2 Gt-C⅐yr Ϫ1 (ϭ 2 ϫ 10 15 g of carbon⅐yr Ϫ1 ), which corresponds to about 35% of the current industrial CO 2 emission rate of about 6 Gt-C⅐yr Ϫ1 . On the basis of temporal changes of the 13 C͞ 12 C ratio in atmospheric and oceanic CO 2 , the annual oceanic uptake of atmospheric CO 2 has been estimated to be 1.6 Ϯ 0.9 Gt-C⅐yr Ϫ1 (2, 9). Tans et al.(1) combined the meridional gradient of atmospheric CO 2 concentration and the net CO 2 flux over the northern oceans to constrain the CO 2 budget and concluded that th...