Summary of the session: When scientists advise policy-makers, they are usually asked to be « policy relevant » rather than « policy prescriptive». Where is the limit between these two concepts? How can politicians use findings brought to them by expert bodies such as the IPCC or the UNSCEAR ? Scientists, who are also citizens, are sometimes encouraged through their work and research to become activitists. Are they still in their role? Does the status of « scientist » grant them more legitimacy? To address such questions, the Shift Project has the pleasure of welcoming James Hansen, a pioneer who has been raising awareness on climate change since 1988, as well as officials from expert bodies and former government representatives.