Climate change 2007: the physical science basis

This contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change is the most comprehensive scientific assessments of climate change during the past (the climate during periods before the development of measuring instruments, including historic and geological time), the present (the average weather over a number of recent decades) and the future (projected long-term average weather changes due to changes in atmospheric composition or other factors). The book also provides an excellent overview on how the science of climate change has progressed, including the methods used, and also shows the recent advances made in the modelling of regional climate change over the African continent. Moreover, the scientific understanding of anthropogenic effects on global climate has improved since the Third Assessment Report, which has led to very high confidence that the global average net effect of human activities over the past 250 years has been one of warning. The book is divided into a summary for policymakers, a detailed technical summary, followed by technical chapters that deal with various aspects of climate change science, including a historical overview, observed changes in the atmosphere, cryosphere and oceans, the climate models used and global climate projections, understanding and attributing climate change and regional climate projections. The summary for policymakers contains easily understandable illustrations and tables and makes clear statements referring to the latest findings. For example, based on the observations of increases in global average air and ocean temperatures, sea level rise, etc., the warming of the climate system is unequivocal. The 73-page technical summary is a comprehensive overview of the detailed technical chapters. A very useful component of this part of the book is a listing and description of the robust findings as well as the key uncertainties of the current understanding of the complexities of global climate change. The chapters that follow contain a large number of excellent illustrations and tables, and each chapter is concluded with several pages of references. Summary statements, including regional responses to climate change, the definitions of circulation indices such as the Southern Annular Mode, etc., are presented in ‘boxes’ of text in the chapters. The chapters also contain answers to frequently asked questions, such as whether or not sea levels are rising, and whether or not the warming of the twentieth century can be explained by natural variability. The book provides strong evidence to support statements such as: (a) global atmospheric concentrations of greenhouse gasses and aerosols have increased markedly due to human activities, (b) warming of the climate system is unequivocal, and at continental, regional and ocean basin scales, numerous long-term changes in climate have