This article tries to explain the French’s beliefs over climate change in light of the American’s beliefs. The global warming paradigm has rapidly imposed itself on public opinion. It is true in USA but also in France. This paradigm leads to the belief that the planet is warming durably, that the origin of this rising temperature is anthropogenic and that reduction of greenhouse gases by various policies is the correct means of fighting this warming. Nonetheless, French opinion is much more scientific than American Opinion. There are three differences. i) In France the respect of hierarchy is stronger than in the USA. ii) The doubt merchants (skeptic) are poorly organized and had no money. iii) and the medias have defending the global warming paradigm. These characteristic explains why the expressive utility to be skeptic is lower in France than USA and why the justification costs of global warming paradigm are also lower in France than in USA. The conversion to the paradigm of global warming is explained, on the one hand, by the prohibitive level of justification costs of the position of the climate change skeptics and on the other hand by the willingness to improve self-image.