Pope Francis, addressing top oil company executives, has said that the world must convert to clean fuel, Reuters reports. “Civilization requires energy but energy use must not destroy civilization,” he told the group at the end of a two-day conference in the Vatican on Saturday. He also noted that climate change was a challenge of “epochal proportions,” saying that the world needs to come up with an energy mix that combats pollution, eliminates poverty, and promotes social justice. The pope wrote a major document on protecting the environment from global warming in 2015.