Pope Francis called on leaders at the COP28 climate summit in Dubai Saturday to step up and "turn a corner" on saving the planet. 

"Let this COP be a turning point: let it demonstrate a clear and tangible political will, leading to an acceleration of the ecological transition," he said. 

The 86-year-old pontiff also said the world should move to end using fossil fuels. 

The speech by Francis, who cancelled his trip to the United Nation climate talks due to the flu, was read by the Vatican's second highest officer, Cardinal Secretary of State Pietro Parolin. 

The transition "must be effective, binding and easy to monitor" and to apply to "four domains: energy efficiency, renewable energy, ending the use of fossil fuels, and education to make our lifestyles less dependent on them," he said.

"Please, let us go forward, not backwards," said the pope, who has made ecology one of the major themes of his papacy and whose 2015 encyclical "Laudato si" ("Praise be") laid out the Vatican's case for defending the environment.  

Last month Francis published another text on climate challenges, "Laudate Deum" ("Praise the Lord"), which called on developed economies to stop using fossil fuels.