We have compared vertical transport of temperature, anthropogenic CO 2, natural radiocarbon ( 14C), and bomb 14C in a global box-diffusion model (B-D) and a three-dimensional (3-D) ocean general circulation model. We have calculated apparent diffusivities (K ap) vertically over the global ocean that range mostly between 4000 and 8000 m 2 yr -1. These K ap agree quantitatively with diffusivities found by fitting B-D models to observed distributions of natural and bomb 14C. We then used these sets of K ap in different runs of a global B-D model. The best agreement (within 3%) between 3-D CO 2 simulations and B-D model runs was found when applying K ap derived from bomb 14C in the surface and from natural 14C in the deep. We have found it appropriate to study global oceanic uptake of anthropogenic CO 2 with B-D model and to validate anthropogenic carbon uptake models using natural and bomb 14C observations. 14C seems less than ideal to validate the convective scheme of general circulation models.