Changes in climate and biota on geologic time scales.

The 1980s saw the emergence of a new approach that is both enhancing our understanding of climatic change on geologic time scales and providing insight into the impact of these climatic changes on the continental and marine biota. This approach (loosely termed 'data-model comparisons') has been applied both to glacial-interglacial changes occurring during the last three million years and driven by variations in the earth's orbit around the sun, and to the slower climatic changes occurring over much longer time scales and driven by tectonic processes. The strength of this approach lies in comparing the results of two independent ways of studying the climate system, and thus providing insight into the strengths and weaknesses of each. Comparisons are made between climatic changes simulated by experiments with General Circulation Models and those reconstructed from fossils. Close agreement between the results of these two independent techniques implies that the key physical processes acting within the climate system have been identified; fundamental mismatches motivate re-examination of both the models and the fossil biotic data.