The Intergovernmental Panel on Climate Change (IPCC) is one of the most significant global assessment bodies established, and it provides the most authoritative and influential assessments of climate change knowledge. This book examines the history and politics of the organisation, and how this shapes its assessment practice and the climate knowledge it produces. Developing a new methodology, this book focuses on the actors, activities, and forms of authority affecting the IPCC's constructions of climate change. It describes how social, economic, and political dynamics influence all aspects of the organisation and its work. The book contributes to understanding the place of science in politics and politics in science, and offers important insights for designing new knowledge bodies for global environmental agreement-making. It is indispensable for students and researchers in environmental studies, international relations, and political science, as well as policymakers and anyone interested in the IPCC.