The effect of ocean warming on Antarctic ice-sheet melting is a major source of uncertainty in estimates of future sea level rise. We compare five melt models to show that ocean warming strongly increases melting. Despite their calibration based on present-day melting, the models disagree on the amount of melt increase. In some important regions, the difference reaches a factor 100. We conclude that using various melt models is important to accurately estimate uncertainties in future sea level rise.