The IPCC has been a scientific success in demonstrating unprecedented global warming, but a radical political failure to convince civil society and politicians. This interview course brings together Dominique Bourg, the environmental philosopher, Jean Jouzel, the paleoclimatologist and IPCC Vice-Chairman until 2015, and Hervé Le Treut, a climate scientist specializing in digital simulation, to answer the following questions: What is climate in general? What is a climate model? How is it built? How many researchers, how long? What adjustments are made once the model is built? How many models are now in operation worldwide? Since when? How are they used? How can their differences be used to produce solid projections? What assessment can be made of fifty years of climate modelling? What part does the researcher's psychology and ideology play in his or her presentation of the phenomena? What can we say about the denialist attacks and the climate sceptic industrial lobbies? What is already irreversible and what is not? These are all essential and fundamental questions that the philosopher and the two leading IPCC specialists attempt to answer by looking back in history and then forward to the future.