My main theme is palaeoclimatology (last millennium and Quaternary), and the study of the impact of global changes on the vegetation (past, present and future), using pollen data, tree-rings and vegetation modelling in Europe, Mediterranean areas and Africa. I have developed tools to map past vegetation and climate and I used these products to validate climate models (PMIP project). In 2008 I co-founded the ECCOREV network (Continental Ecosystems and Environemental Risks) to promote interdisciplinarity in environmental sciences, in particular with social sciences, and in 2012 the Laboratory of Excellence OT-Med to study of the risks related to climate change and natural hazards in the Mediterranean Basin. I launched in 2015 with W. Cramer, the Mediterranean group of experts on environmental and climate changes (MedECC), to transfer scientific knowledge on climatic change to the society actors of both sides of the Mediterranean. I am a lead author for the IPCC special report on the impact of a 1.5°C global warming (publication in 2019).