Several models of open-ocean tidal elevations have rms accuracies on the order of 1 cm. These are either purely empirical, or involve assimilations of data into hydrodynamical models. We have adapted the Hallberg Isopycnal Model (HIM) to be a forward model of global tides. Following previous work, we show that the accuracy of forward models is affected by the parameterized dissipation occuring over rough topography. This is because tidal amplitudes are sensitive to the amount of dissipation. We explore the effects of self-attraction and loading and nonlinear interactions between different frequency components on the simulations. Our diurnal tides are nearly as accurate as those of the data-derived models, but this is not yet true of our semidiurnal tides. We have begun doing global simulations of baroclinic tides, and of paleo-tides. After calibrating the dissipation parameters against the present-day tides, we will estimate tides and tidal dissipations during the last glacial maximum. Of particular interest is whether the amount of abyssal dissipation was different with a lower sea level, with possible implications for the large-scale overturning circulation.