"If we don't go back we will go down," he warned reporters on Monday. "That is true. You can see the effects of climate change with your own eyes and scientists tell us clearly the way forward. "All of us have a responsibility. All of us. Some small, some big. A moral responsibility, to accept opinions, or make decisions. I think it is not something to joke about." He then quoted a phrase from the Old Testament: "Man is stupid, a stubborn, blind man." "Those who deny it (climate change) should go to the scientists and ask them," the Pope said. "They are very clear, very precise."