Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 52. The principal aim of this symposium was to describe the contributions which are made by each of the disciplines represented in the IUGG to the study of climate change. In order to present a balanced program, the Symposium was composed of invited reviews but other viewpoints were put forward during general discussion. The themes covered reflect the interests of the seven IUGG Associations and include volcanism; biogeochemistry; land hydrology; modeling climate, past and present; cryosphere; paleoclimates; land?]surface processes; tropical oceans and the global atmosphere; clouds and atmospheric radiation; aeronomy and planetary atmospheres; and modeling future climate changes.