Résumé en anglais

This paper is an excerpt from the last chapter of Jean-Marie Chevalier’s last book «Les grandes batailles de l’énergie». The author explains what he calls «the equation of Johannesburg» named from the last Earth summit. The most important challenge of the XXIst century, and the most important battle to win is to find out the right combination between the satisfaction of our energy needs, the responsible management of the climate, and the necessary development of the South. The author indicates what should be the six major priorities of the century :identify and measure the environmental costs associated to each form of energy – put energy efficiency as a major international priority – reduce greenhouse gas emissions – use energy to promote economic development and the fight against poverty – make people and organization aware of their responsibilities – invent new forms for a better regulation of the world economy.