The Evolution of Climate and Biosphere During the Past 20 Million Years

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Abstract ATM-9806918 Kutzbach, John E. University of Wisconsin Title: The Evolution of Climate and Biosphere During the Past 20 Million Years Studies of the Earth's history show that the large climate changes of the past have been associated with equally large changes in the biosphere, the deep ocean, the large continental ice sheets, and the earth's carbon cycle. This award supports a study of large climate changes of the past using numerical models of the atmosphere, the land surface, terrestrial ecosystems, oceans, ice- sheets, and components of the carbon cycle. In the past, large climate changes were initiated by tectonically-related changes in land-ocean distribution, by the rise and fall of mountains, and by changes in earth's orbital parameters. By prescribing changes in these "external" forcings of climate, it is possible to use models to simulate the climate's direct response , and to study possible feedback mechanisms involving the biosphere, or the cryosphere that might amplify or dampen the direct response. The great advantage of using the past as a "testing ground" for studies of climate change is that geological records from terrestrial and marine environments can be compared with the results of the simulations to evaluate the accuracy of the models. The specific testing ground chosen for this study is the most recent major glaciation that began about 20 million years ago. Large changes in the atmospheric concentration of CO2 probably played a role in situation and will be an important focus of the project. The results of this work will lead to improved understanding of the mechanisms involved in this large climate changes of the past and will help assess the accuracy of models being developed to estimate possible climate changes of the future.