Book excerpt: This book is the first in a series of assessments of regional climate change. Irreversible changes to regional biogeochemistry, and terrestrial and marine ecosystem functioning are brought about by increases in population, intensified land use, urbanization, industrialization and economic development. These may have global as well as regional consequences. The objectives of the assessments are, (i) to better understand how human activities in regions are altering regional atmospheric, terrestrial, and marine environments, (ii) to provide a sound scientific basis for sustainable regional development, and (iii) to develop the capability of predicting changes in global-regional linkages in the Earth System and to recognize the future consequences of such changes. This book describes such a study for monsoon East Asia, providing a state-of-the-art summary of what we already know, and serves as a basis for identifying knowledge gaps that require study.