The axial dispersion model has been commonly used to describe gas phase flow in bubble columns. Scatter in dispersion coefficients reported to date may be a result of the misuse of the axial dispersion model when a convective model would be more appropriate. Using simple tests with radioactive tracer response curve moments, convective and dispersive behaviours are differentiated. A convective model is presented. The model fits both tracer response curves and mean gas velocity well in both the bubbly and churn turbulent flow regimes, and may be used as a technique to calculate bubble rise velocity distributions.