Pope Francis: Climate change mostly man-made
18 June 2015 Last updated at 22:56 BST
Pope Francis has blamed human greed and selfishness for damaging the planet - and he has called on everyone to take action to stop climate change.
The comments were made in a papal encyclical, a letter from the Pope explaining his latest teaching.
He called on richer parts of the world to make changes in lifestyle and energy consumption in order to avert the unprecedented destruction of the ecosystem.
The BBC's Caroline Wyatt reports.