This Open Access book shows how expert consensus pervades all areas of science. It explores, in particular, the role of consensus in establishing scientific truth, in guiding professional practice and policy and agreeing on what are acceptable scientific methodologies. For some scientific issues, a consensus forms spontaneously among scientists working on a topic, while for others, where the issues are complex, a formal deliberative consensus process is commonly needed. Deliberative consensus processes are becoming more important as scientists increasingly deal with complex multi-disciplinary issues of policy importance such as climate change due to human activity. While deliberative consensus processes are commonly used, they often lead to criticism from consensus skeptics. The book argues that deliberative consensus processes in science can be improved and proposes a number of realistic ways forward, ending with a discussion of whether communicating the scientific consensus on a topic is a good way to persuade the public.