This essay explores the history and consequences of scientific consensus building activities by the Intergovernmental Panel on Climate Change (IPCC) on the topic of dangerous anthropogenic climate change. A broad view of consensus is provided in the context of the philosophy of science and the social and psychological issues that contribute to bias. The role of scientific consensus in policy making is discussed. An overview is provided of critiques of the IPCC consensus process. A summary of recommendations is provided aimed at improving the interface between climate science and policy in ways that can support decision making associated with growing implications of ‘messy wickedness’ of the climate change problem.