Pope Francis met with oil and gas executives and investors in a closed-door session at the Vatican on Saturday to sound the alarm on fossil fuels dire threat to humanity and urgently call for greater efforts to develop alternative energy.

There is no time to lose , the pontiff told them. This is a challenge of epochal proportions. Civilization requires energy, but energy use must not destroy civilization.

He praised business leaders for adjusting their business practices to reduce emissions as climate change worsens. But the pontiff said it wasnt enough, and that a radical transition to new forms of energy must happen now. Failure to adequately address the issue will mean a catastrophic rise in global temperatures, harsher environments and increased levels of poverty, he said.

With each month that passes, the challenge of energy transition becomes more pressing, Francis warned, according to a transcript of his speech provided by the Vatican. Serious efforts be made to transition to a greater use of energy sources that are highly efficient while producing low levels of pollution.

He asked ominously: Will we turn the corner in time? No one can answer that with certainty.

He spoke to the business leaders on the second day of an energy summit Energy Transition and Care for Our Common Home co-sponsored by the University of Notre Dame. He called on those present to be the core of a group of leaders who envision the global energy transition in a way that will take into account all the peoples of the earth as well as future generations and all species and ecosystems.

Among the 40 executives who attended the meeting were BlackRock Inc. chief executive Laurence Fink, Exxon Mobil Corp. chief executive Darren Woods and British Petroleum CEO Bob Dudley, The Wall Street Journal reported .

The attitude of the pope on fossil fuels and climate change presented a dramatic contrast to the position of President Donald Trump , a global warming skeptic who skipped out of the G7 summit early Saturday before sessions on climate change and the environment. Trump, who pulled the U.S. out of the Paris Climate Accords, once called global warming a hoax invented by the Chinese .