Lord Stern urged world leaders to deliver an ambitious climate change treaty at next year's Paris Summit. Speaking yesterday at the start of the second week of the UN Climate Summit in Lima, Stern, who authored the influential Stern Review on the economics of climate change, said the final treaty should be "dynamic" and as such it is not necessary to ensure the emissions targets nations agree to are legally-binding.

"Some may fear that commitments that are not internationally legally-binding may lack credibility,” he said. “That, in my view, is a serious mistake. The sanctions available under the Kyoto Protocol, for example, were notionally legally-binding but were simply not credible and failed to guarantee domestic implementation of commitments."

His comments come amidst reports that the US and EU are at odds over the legal standing for the proposed treaty with the EU and many poorer nations demanding that emissions reduction targets are put on a legal footing, while the US has repeatedly argued that binding targets are unnecessary. Privately, US diplomats are sceptical the US Congress would approve any targets that are legally-binding, while emerging economic superpowers such as China and India may have shown a greater willingness to discuss voluntary emissions targets in recent months, but remain opposed to binding goals.

Stern released a new report recommending a series of proposals for the Paris Treaty, will argue that the agreement could deliver a significant boost for global decarbonisation efforts without necessarily relying on binding emissions targets. He also stressed that any agreement should have the ability to raise ambition over time in order to ensure temperature rises keep to the agreed 2C goal.