U.N. Secretary-General Antonio Guterres, warning that countries are retreating from a promise made nearly three years ago to save the planet from the most catastrophic effects of climate change, on Monday scolded world leaders and called on them to “break the paralysis” on reining in greenhouse gas emissions.

“Climate change is the defining issue of our time, and we are at a defining moment,” he said at U.N. headquarters in New York. “Scientists have been telling us for decades. Over and over again. Far too many leaders have refused to listen.”

“If we do not change course by 2020, we risk missing the point where we can avoid runaway climate change,” Guterres said.

His remarks came with countries around the world far short of meeting the goals they set for themselves under the 2015 Paris accord to reduce the emissions that have warmed the planet over the past century. The next round of climate negotiations is scheduled for this year in Poland.

One of the big tests at those talks will be whether countries, especially industrialized countries that produce a large share of global emissions, will set higher targets for reducing their emissions.

“The time has come for our leaders to show they care about the people whose fate they hold in their hands,” Guterres said.

His speech came days before a high-level climate meeting in San Francisco, spearheaded by Gov. Jerry Brown of California, meant to demonstrate what businesses and local leaders have done to tackle climate change.

Guterres sought to make the case that a shift away from fossil fuels like oil and coal would create jobs and bolster economies. Rebutting critics who argue that such a shift would be costly, he called that idea “hogwash.” He cited the steps private companies are taking to wean themselves away from polluting fossil fuels, though he said such actions are plainly insufficient. He said, “The transition to a cleaner, greener future needs to speed up.”