GEOLOGICAL EVALUATION OF CLIMATE GENERAL-CIRCULATION MODELS AND MODELIMPLICATIONS FOR MESOZOIC CLOUD COVER

General Circulation Models (GCMs) are currently used to predict future global change. However, the robustness of GCMs can, and should, be ev aluated by their ability to simulate past climate regimes. Their succe ss in 'retrodiction' can then be assessed by reference to the testimon y of the geological record. Geological evidence provides a database wh ich can be used in the estimation of sea surface temperatures and othe r proxy data useful in palaeoclimatic studies. These data can then be used to refine the prescribed boundary conditions for running GCMs the mselves. Results of modelling experiments confirm a generally warmer M esozoic earth with arid tropics and convective rainfall higher over th e oceans than at present. Circum polar wetlands are also indicated. Mo delled cloudiness is also higher in the Mesozoic, contributing to gree nhouse conditions and possibly influencing terrestrial biomes and mari ne ecosystems.