Warm Climates in Earth History, Brian T.

It would be profoundly incorrect to assert that long-term episodes of past global warmth, whether driven by increased atmospheric ‘‘green-house’ ’ gas concentrations or not, represent analogs to the predicted future anthropogenically induced global warming. The rate and mag-nitude at which the present atmospheric composition is changing probably are significantly higher than any natural event, as presently known. It is also rather unlikely that most such rapid events, if they occurred, would be faithfully recorded in sedimentary rocks of most environments unless their effects were long lasting. Yet understand-ing the nature of past events provides important insight into climate processes and can help to refine quantitative models for global warm-ing. Study of episodes of past global warmth using data-based climate reconstructions and numerical models contributes to the solution of two unrelated but important problems. First, numerical models act as a testing ground for hypotheses based on inferences from data on the basis of a quantitative approach. Secondly, the data furnish con-straints for testing the efficacy of different climate models in climate hindcasting or forecasting. The first objective satisfies our intellectu-al quest for an understanding of the controls of climate variability in the past, and the second objective focuses on societal implications of global change in assessing the ability of climate models to predict the consequences of changing boundary conditions such as pCO2. The first objective is the obvious focus of the collected papers in Warm Cli-mates in Earth History, although the second is implicit and acknowl-edged in the book’s Preface. Warm Climates in Earth History consists of 14 primarily multiau-thored chapters contributed by a total of 34 different authors. In es-sence, the individual chapters are contributed papers that resulte