Existing data on CO2 fluxes between air and sea have been calculated by assuming, incorrectly, that the thermodynamic driving force for the CO2 flux is provided solely by the CO2 partial pressure difference between the two phases. Because both heat and matter transfer occur under non-equilibrium conditions, with finite temperature and composition differences across the interface, a proper description of transport at the air-water interface requires the use of irreversible thermodynamics, according to which the heat and matter fluxes are coupled through the heat of solution of the gas. The present treatment shows that the driving force for CO2 transport due to the temperature difference across the interface is comparable with that arising from the partial pressure difference. ¿ American Geophysical Union 1991