Human influence on the global environment has increased considerably this century. In the early 1900s there were severe local environmental problems, mainly in densely populated areas, but the influence on the global environment was hardly noticeable. The situation at the end of the century has changed drastically. Anthropogenic influences on the overall composition of the atmosphere are already partly dominating natural processes. The stratospheric ozone destruction by CFCs and other artificial chemical constituents and the climate warming caused by increased greenhouse gas emission are problems that are now facing humankind. It is to be expected that the environmental problems will be more severe in the future because of the increased population and the likelihood that advanced industrialization will encompass the whole world. Environmental problems are by their nature complex, because they often include series of intricate feedback processes. They cannot therefore be predicted exactly, and major surprises in the way the environment will respond to anthropogenic and other influences must be expected. An area that requires much more scientific attention is the interaction between the biosphere, the geosphere, and the climate. That such major interactions occur is well documented from palaeorecords, which show that the past climate of the Earth was very different from what it is today. To address these issues a Study Conference on "Geosphere-Biosphere Interactions and Climate" was organized by the Pontifical Academy of Sciences 9-13 November 1998 at the headquarters of the Academy in Vatican City. A group of some 25 scientists, experts on different aspects of these problem areas, was invited to determine the present state of our scientific knowledge and to outline a long-term strategy for future research and possible lines of action that society can take based on what we now know. The specific aim of the conference that served to guide the individual contributions is described in the Preface. This book contains the revised version of 18 contributions from the Study Conference on "Geosphere-Biosphere Interactions and Climate." They have been arranged by a broad subdivision of the topic into five major parts, examining first the problem with the increasing anthropogenic influences on the climate and the global environment and second the specific human perspective of climate change. This is followed by reviews of the key methodologies that are central in understanding the interactions between the biosphere, geosphere, and climate. The third part deals with the mathematical modeling of the Earth's system. This approach is currently the main tool to predict weather and climate, including simulations of future climate change. This methodology is now being extended to address a wider range of problems, including the dynamical changes of the biosphere and the geosphere. This incorporates modeling studies of the climates that existed far back in the early history of our planet. The fourth part of this volume deals with the reconstruction of past climates with the help of different paleo data. There have been spectacular contributions in recent years, particularly from the analyses of ice cores in Greenland and the Antarctic, which have significantly changed our concept of past climate. This includes indications of rapid climate changes over periods of a few decades for which, so far, there is no comprehensive explanation. An understanding of such events requires a more in-depth understanding of the feedback processes between climate, biosphere, and geosphere. In the fifth part, summaries are given of the strategies for organizing the future science program and the particular roles of WCRP (World Climate Research Programme) and IGBP (International Geophysical and Biological Programme). We would like to express our deep appreciation to the Pontifical Academy of Science for organizing the Conference on "Geosphere-Biosphere Interactions and Climate" and for the Academy's support toward this publication. We would also like to acknowledge the valuable assistance of Dr. Annette Kirk in the editorial work. Finally, we express the hope that publication of these proceedings will advance the knowledge and further the understanding of the complex issues addressed by the contributors.
The Editors