Abstract
The longer we delay action, the more measures to be taken will be brutal. It is already possible to take “no regrets” or “multiple dividends,” i.e., which lead profit to both the economy and society, thus justifying their adoption while limiting efficiently the emissions of greenhouse gases emissions and protecting the environment. We must act now, not to prevent climate change now initiated and unavoidable but to minimize the importance and especially rapidity of the phenomenon. This is indeed the speed of the upheaval which will condition the importance of climate instabilities at the origin of natural disasters, as well as the adaptability of ecosystems and human societies.