Julien holds a PhD in Economics, specialising in environmental and commodity economics. He began his career as a "scarce resources" economist at the Ministry of Foreign Affairs. He was in charge of environmental and raw materials issues. From 2011 onwards, he also focused on monitoring the eurozone crisis. Julien then worked at Lépac, the laboratory preparing the Dessous des cartes programme broadcast on Arte. Back at the MFA in 2015, he joined the Centre for Analysis, Forecasting and Strategy to monitor macroeconomic, financial and trade issues on the one hand, and environmental issues on the other. He was thus able to contribute to the operational proposals for the COP21. Julien then worked as a project manager for sustainable development at France Stratégie on the value of climate action and the carbon cost of metals. He was also the initiator of the "Sustainability" seminar series. He has now joined the High Council for the Climate and contributes to the organisation’s various reports. He pays particular attention to the consideration of ecological issues from a systemic perspective. In parallel to his activities, Julien is an associate professor at Paris I Panthéon-Sorbonne and at the École normale supérieure.