The hydrologic cycle: A major variable during earth history

Abstract

Water plays a central role in nearly all Earth processes and in the evolution of the planet. However, despite the significance of water, our knowledge of it as part of the global system in meager. In fact, for paleoclimatology the primary focus on planetary evolution is centered on temperature variations and little attention is directed towards the role of the hydrologic cycle. Model analyses presented here based on a series of simulations utilizing the Community Climate Model (CCM) at the National Center for Atmospheric Research demonstrate that the hydrologic cycle is highly sensitive to climate change and to climatic forcing factors such as changes in atmospheric carbon dioxide, plate tectonics, paleogeography, and orbital variations. The implications of the large sensitivity of the hydrologic cycle are of considerable importance. The role of water in explaining much of the Earth's record has probably been underestimated. The importance of water in global change in Earth history may also suggest that the hydrologic cycle should be of primary interest in studies of future global change.