THE EFFECTS OF VARIABLE BIOME DISTRIBUTION ON GLOBAL CLIMATE

In projecting climatic adjustments to anthropogenically elevated atmos pheric carbon dioxide, most global climate models fur biome distributi on to current geographic conditions. Previous biome maps either remain unchanging or shift without taking into account climatic feedbacks su ch as radiation and temperature. We develop a model that examines the albedo-related effects of biome distribution on global temperature. Th e model was tested on historical biome changes since 1860 and the resu lts fit both the observed temperature trend and order of magnitude cha nge. The model is then used to generate an optimized future biome dist ribution that minimizes projected greenhouse effects on global tempera ture. Because of the complexity of this combinatorial search, an artif icial intelligence method, the genetic algorithm, was employed. The me thod is to adjust biome areas subject to a constant global temperature and total surface area constraint. For regulating global temperature, oceans are found to dominate continental biomes. Algal beds are signi ficant radiative levers as are other carbon intensive biomes including estuaries and tropical deciduous forests. To hold global temperature constant over the next 70 years this simulation requires that deserts decrease and forested areas increase. The effect of biome change on gl obal temperature is revealed as a significant forecasting factor.