The U.N.'s top climate official said on Sunday that she expects governments to make a long-delayed decision on whether industrial countries should make further commitments to reduce emissions of climate-changing greenhouse gases.

Amid fresh warnings of climate-related disasters in the future, delegates from about 190 countries were gathering in Durban for a two-week conference beginning on Monday. They hope to break deadlocks on how to curb emissions of carbon dioxide and other pollutants.

Christiana Figueres, head of the U.N. Climate secretariat, said the stakes for the negotiations are high, underscored by new scientific studies.

Under discussion was “nothing short of the most compelling energy, industrial, behavioural revolution that humanity has ever seen,” she said.

Archbishop Desmond Tutu led a rally at a soccer stadium later on Sunday urging negotiators to be more ambitious during what were expected to be difficult talks. Unseasonably cold, windy weather kept the crowd to a few hundred spectators.

Hopes were scrapped for an overall treaty governing global carbon emissions after the collapse of talks at a climate summit in Copenhagen two years ago. The “big bang” approach has been replaced by incremental efforts to build new institutions to help shift the global economy from carbon-intensive energy generation, industries and transportation to more climate-friendly technologies.

But an underlying division between rich and poor countries on the future of the 1997 Kyoto Protocol has stymied the negotiators.

This week the World Meteorological Organisation is due to report on global temperatures for 2011.

More In: Comment | Opinion