was chairman of the International Climate Commission of the International Union of Geodesy and Geophysics (1987–1993) and of the Paleoclimate Commission of the International Union of Quaternary Research (1987–1995); president of the European Geophysical Society (2000–2002), co-creator of the European Geosciences Union of which he is honorary president; member of the First Scientific Steering Committee of the International Geosphere-Biosphere Programme on Global Changes of the Past (1988–1990), Committee which is at the origin of PAGES. In 1991, he was the initiator of the Paleoclimate Modelling Intercomparison Project (PMIP). For the Commission of the European Communities, he was chairman of the Coordination Group on Climate Processes and Climate Change of the Climatology and Natural Hazards Program (1988–1992), of the External Advisory Group on Global Change, Climate and Biodiversity (2000–2002) and member of the Contact Group of the Climate Programme on Reconstruction of Past Climate, Climate Models and Anthropogenic Impacts on Climate from 1980 to 1983 (groups which are at the origin of the CEC Framework Programme). For the Scientific Committee of NATO, he was chairman of the Special Programme Panels on the Science of Global Environmental Change (1992) and on Air-Sea Interactions (1981) and of the programme Advisory Committee of the International Technical Meeting on Air Pollution Modelling and its Applications (1980–1985). He was also member of committees in charge of advising policy makers and scientific institutions, in particular the European Environment Agency (EEA, 2002–2009), the European Science Foundation (ESF), Gaz de France (1994–1999 ) and Electricité de France (1998–2009). He was a member of the scientific committee of universities and research institutes, among which Laboratoire des sciences du climat et de l'environnement, Laboratoire de Météorologie Dynamique, Département Terre-Atmosphère-Océan de l'Ecole Normale Supérieure, Institut Paul Simon Laplace et Collège de France in Paris, Laboratoire de Glaciologie et de Géophysique de l'Environnement and the European University and Scientific Pole of Grenoble, LEGOS in Toulouse, Météo-France, Hadley Centre for Climate Prediction and Research in Great-Britain and Beijing Normal University. He is a voting member of the BAEF (Belgian American Educational Foundation, Herbert Hoover Commission for Relief in Belgium) which he was fellow in 1970-1971. He has organised and chaired international meetings, among which are the First International School of Climatology on Climatic Variations and Variability, Facts and Theories at the Ettore Majorana Center of Erice in Sicily, from 9 to 21 March 1980, the symposium Milankovitch and Climate (with J. Imbrie) at the