Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer based separation technique, we estimate a global oceanic anthropogenic CO 2 sink for the period from 1800 to 1994 of 118±19 Pg C. The oceanic sink accounts for ~48% of the total fossil fuel and cement manufacturing emissions, implying that the terrestrial biosphere was a net source of CO 2 to the atmosphere of about 39±28 Pg C for this period. The current fraction of total anthropogenic CO 2 emissions stored in the ocean appears to be about one third of the long term potential.