[1] We re-assess the constraints that estimates of the global ocean excess radiocarbon inventory (IE) place on air-sea gas exchange. We find that the gas exchange scaling parameter aq cannot be constrained by IE alone. Non-negligible biases in different global wind speed data sets require a careful adaptation of aq to the wind field chosen. Furthermore, aq depends on the spatial and temporal resolution of the wind fields. We develop a new wind speed- and inventory-normalized gas exchange parameter aqN which takes into account these biases and which is easily adaptable to any new estimate of IE. Our study yields an average estimate of aq of 0.32 ± 0.05 for monthly mean winds, lower than the previous estimate (0.39) from Wanninkhof (1992). We calculate a global annual average piston velocity for CO2 of 16.7 ± 2.9 cm/hr and a gross CO2 flux between atmosphere and ocean of 73 ± 10 PgC/yr, significantly lower than results from previous studies.