This book is the result of a research project entitled "Reference function for Global Air Pollution/C0 " initiated by RIVM. It deals with the description 2 of a computer simulation model of the greenhouse effect. This model, IMAGE, tries to capture the fundamentals of the complex problem of climate change in a simplified way. The model is a multidisciplinary product and is based on knowledge from disciplines as economics, atmospheric chemistry, marine and terrestrial biogeochemistry, ecology, climatology, and glaciology. This book might be of interest for anyone working in the broad field of climate change. Furthermore, it can be useful for model builders, simulation experts, mathematicians etc. A PC version of the model will become avail- able free of charge. Requests can be sent to the author. Although being the only author of this book, I could never have written it without the help of many other people. First of all I would like to thank Koos Vrieze, originally a colleague at RIVM, later my professor. Without his inspiring attitude I would have never finished this thesis. I am also very grateful to RIVM for giving me the opportunity to write this thesis. lowe many thanks to Hans de Boois and Rob Swart for their support and assis- tance during the research. Furthermore, I would like to thank my trainees who have substantially contributed to the contents of this book.