UN chief Antonio Guterres on Thursday warned that the world is "losing the race" on climate change as he demanded that governments make bolder commitments beyond the Paris accord.
"Climate change is the defining issue of our time. We are losing the race," he said on the margins of the World Economic Forum in Davos.
"It is absolutely central to reverse this trend."
Guterres said he was "not hopeful" that nations would find the resolve but stressed: "We need political will and we need governments who understand that this is the most important priority of our times."
The Paris climate accord has been shaken by the withdrawal of the United States under President Donald Trump, and by threats to do the same by Brazil's new hard-right leader Jair Bolsonaro.
The UN secretary-general said the commitments made in Paris were already "not enough".
"If what we agreed in Paris would be materialised, the temperature would rise more than 3.0 degrees (Celsius)," he said on a Facebook Live broadcast from Davos.
"We need countries to make stronger commitments," Guterres said, calling for more measures to mitigate against climate change, adapt to it, and financial aid for poorer countries.