"Let me be very clear again: the phase-out of fossil fuels is essential and inevitable. No amount of spin or scare tactics will change that. Let's hope it doesn't come too late," he said at the World Economic Forum in Davos.
Nearly 200 countries agreed at the COP28 climate summit last month to begin reducing global consumption of fossil fuels to avert the worst of climate change.
The deal, struck after two weeks of negotiations, was meant to send a message to investors and policy-makers that the world must part with fossil fuels.
"We must act now to ensure a just and equitable transition to renewable energy," Guterres added.
