Pope Francis told world leaders gathered at the United Nations on Monday that climate change was a "challenge of civilisation" they had to tackle while a window of opportunity was still open.
In a video broadcast to the U.N. Climate Action Summit, Francis called for honesty, responsibility and courage to face what he called "one of the most serious and worrying phenomena of our time".
Leaders had to conjure up the political will to tackle it.
"While the situation is not good and the planet is suffering, the window of opportunity is still open. We are still in time," he said. "Let us not let it close. Let us open it with our determination to cultivate integral human development, to ensure a better life for future generations. It is their future, not ours."
Francis, who has called for the gradual elimination of fossil fuels, said the climate change crisis should make people re-think models of consumption and production.
"We are facing a 'challenge of civilization' in favour of the common good. And this is clear, just as it is clear that we have a multiplicity of solutions that are within everyone's reach, if we adopt on a personal and social level a lifestyle that embodies honesty, courage and responsibility," he said.
Francis wrote an encyclical in 2015 on environmental protection, which was a main topic of his trip to Africa earlier this month.