Foreword - Following recent criticism of IPCC, abundantly reported in certain media, it appears necessary to recall just what the IPCC is and how its reports are prepared and approved. Organization of IPCC appeared imperative after scientific results had been obtained concerning:
•1) the role of the greenhouse effect in the climate system, which was and is a thoroughly established physical fact;
•2) the discovery that atmospheric concentrations of certain greenhouse gases (GHG) in the global atmosphere have been rising substantially because of growing GHG emissions linked to human activities; and
•3) the resulting growing risk of provoking dramatic global climate change. Even though some errors have been detected in its voluminous reports, the IPCC constitutes a model for dialog of scientists and decisionmakers.


Michel Petit