This book provides a synthesis of the past decade of research into global changes that occurred in the earth system in the past. Focus is achieved by concentrating on those changes in the Earth's past environment that best inform our evaluation of current and future global changes and their consequences for human populations. The book stands as a ten year milestone in the operation of the Past Global Changes (PAGES) Project of the International Geosphere-Biosphere Programme (IGBP). It seeks to provide a quantitative understanding of the Earth’s environment in the geologically recent past and to define the envelope of natural environmental variability against which anthropogenic impacts on the Earth System may be assessed. A set of color overhead transparencies based on the figures in the book is available free on the PAGES website (www.pages-igbp.org) for use in teaching and lecturing.