Despite the many internal and external controversies it has had to face since its founding in 1988, the Intergovernmental Panel on Climate Change (IPCC) has managed to make a name for itself as a model of international expertise. It has assembled thousands of individuals, scientists and diplomats alike, in a highly successful experiment in cooperation on an international level. Though far from the original vision its founders, who had imagined it as an informal structure serving decision-makers, the IPCC has become an institution supplying an unprecedented form of multilateral scientific diplomacy. This equally unprecedented work aims to tell its story.