Greenhouse gases predicted to peak earlier than pledged

China's output of greenhouse gases is set to start falling five years earlier than the largest emitter has pledged, according to a study by UK academics that indicates an increased chance of global warming staying at safe levels.

The forecast of a peak in 2025 in a paper published on Monday by former World Bank chief economist Nicholas Stern suggests China is acting faster than promised to shift to clean energy from fossil fuels. President Xi Jinping last year pledged that his country's emissions would peak by 2030.

"China's international commitment to peak carbon dioxide emissions around 2030 should be seen as a conservative upper limit from a government that prefers to under-promise and over-deliver," Stern, now a professor at the London School of Economics, and his co-author, Fergus Green, wrote in the paper.