The world could buy itself 15 years of breathing space for fighting climate change, one of the world's top climate modellers argued on Monday.

Peter Cox at the University of Exeter, UK, was speaking at the Planet Under Pressure meeting in London, where more than 2800 scientists gathered to discuss fears that Earth's life-support systems are under intense stress from human activity.

The trick, he says, is to widen our attack on greenhouse gases from carbon dioxide to include the second most significant greenhouse gas - methane. "Methane is a more important control on global temperature than previously realised. The gas's influence is much greater than its direct effect on the atmosphere," says Cox. Curbing methane, he adds, may now be the only way to prevent dangerous warming.

We release methane in many ways - leaks from gas pipelines and coal mines, from landfills, the guts of livestock and rice paddies. Curbing these emissions would bring a manifold benefit for climate, says Cox.

He has studied the way CO2 and methane influence plant growth, and says that these feedback mechanisms mean action on methane could have twice the expected punch.