Born in 1935, Michel Petit attended the French Ecole Polytechnique and Ecole Nationale Supérieure des Télécommunications (now called Télécom Paris Tech). After about 20 years of research at the National Center for Telecommunication Studies (Centre national d'études des télécommunications) on the ionized part of the Earth's upper atmosphere, or the ionosphere, he held various management positions in diverse research organizations: director of the National Institute of Astronomy and Geophysics (Institut national d'astronomie et de géophysique), scientific director of the Earth, Ocean, Atmosphere, and Space department at the National Center for Scientific Research (Centre national de la recherche scientifique, CNRS), adviser on science and technology for the Permanent Representation of France to the European Communities, director of international affairs at the ministry in charge of research, managing director at the ministry in charge of space affairs, director of research and economic and international affairs at the Ministry of the Environment, and deputy managing director of research at Ecole Polytechnique. Since retiring in 2000, he has continued to work for the Intergovernmental Panel on Climate Change (IPCC), for which he was a bureau member from 1992 to 2002 and international director of the transversal theme "scientific uncertainty and climate risk management" for the Fourth Assessment Report (2007). In 2003, he published the book What's the Greenhouse Effect? (Vuibert), presenting a simplified account of the panel's conclusions. It was reedited in 2004. He is also president of the board of directors of the Oceanographic Institute Foundation Albert I, Prince of Monaco, president of the terminology and neology committee of the Academy of Sciences as well as representative of the Academy's General Commission of Terminology, editor in chief of the review Geoscience (reports from the Academy of Sciences), and president of the association of friends and former members of CNRS.