Paleoenvironmental modelling and global change

Abstract

The reconstruction of past environments using infonnation extracted from the geological record, even in the absence of models of paleoenvironmental change that are able to explain the observed variability, will clearly play an extremely important role in the International Geophere-Biosphere Program. Such data provide the only framework within which we may come to understand what constitutes the natural long time scale variability in the climate system. If we wish to prove an anthropogenic effect then we shall have to show that the signal at issue (e.g. an increase of mean surface temperature, a decrease of continental ice volume, or an eustatic rise of sea level) is not plausibly of internal origin. Only if we can embed our understanding of the climate in an appropriate (mechanistic) mathematical model, however, will we be able to effect a truly satifactory separation between internal and anthropogenically driven variability and therefore truly understand what the future may have in store as the responds to the various stimuli to which it is subject. Simply put we need models in order that we may predict the future on the basis of the present and appropriately recent past. On timescales of hours to days only the similarly fast physics of the climate plays any important role in determining intrinsic predictability and therefore only the planetary atmosphere (say) need be explicitly included in the model. As the timescale of interest increases, additional components of the earth system