In an encyclical published today, Pope Francis issues a powerful appeal to the world’s 1.2 billion Catholics, and humanity in general, to take responsibility for the planet and ward off global warming. Couched in simpler language than popes normally use, the document (a draft of which was leaked on Monday) says that human activity is clearly responsible for global warming and rising sea levels, and argues that countries which have grown rich from burning fossil fuels have a duty to bear the costs of necessary economic transition. The encyclical is clearly designed to influence a summit in Paris in November, which is being presented as a last chance to limit carbon emissions and avert disastrous warming. It is the first time the world’s largest religious organisation has thrown the full weight of its influence behind the effort to conserve and cool the Earth.