A previously formulated dynamical model of the late Pleistocene ice ages (based on the hypothesis that the global CO2 system can provide the instability to drive a natural oscillation involving feedbacks between the cryosphere, atmosphere, and ocean) is extended to include (1) additive earth orbital forcing (summer insolation changes at 65¿N) and (2) tectonic forcing in the form of a postulated variation in the multiplicative parameters (rate constants) of the model system. The structural (e.g., bifurcation) properties of the model are examined in detail to reveal the regions of parameter space wherein the geologically inferred features of the full Pleistocene can be simulated, including the observed chronology, the phase relationships between ice, CO2, and North Atlantic Deep Water formation, and the mid-Pleistocene transition. ¿ American Geophysical Union 1990