During the 1980s, Suki Manabe was one of the first to use paleoclimate simulation as a means of evaluating the realism of model-derived climate sensitivity. As the demand for reliable projections of future climate has grown dramatically, evaluation of climate sensitivity has remained an important application of paleoclimate modeling. At present, paleoclimate simulation and empirical analysis of paleoclimate data are recognized as important tools for estimating the sensitivity of the real climate system. Motivated by advances in climate modeling and the development of new paleotemperature proxies, new model-data comparisons will be presented and the implications for future climate will be discussed.