Climate change poses as great a threat to the world as the nuclear arms race, scientists warned yesterday as they called on leaders to take urgent action to tackle the problem.

The scientists and Nobel laureates attending a three-day conference hosted by St James's Palace drew up a memorandum calling for global greenhouse gas emissions to peak by 2015. The memorandum from the experts, who included the US energy secretary Steven Chu, said a new global deal on emissions expected at the UN conference on climate change in Copenhagen in December was urgently needed.

It must undertake to cut greenhouse gases by half by 2050, the document urged. And while developed countries should take the lead, with cuts of 25 per cent to 40 per cent by 2020, every nation must act, on the "firm assumption that all others will also act".

Download the new Independent Premium app Sharing the full story, not just the headlines

Professor Hans Schellnhuber, director of the Potsdam Institute for Climate Impact Research in Germany, said that with "probably the biggest concentration of brains on the planet" drawing up the memorandum, it could be more vital than many mass protests on climate change. "We are in a crisis as deep as the times of the arms race," he added.

The memorandum from the conference said that without protecting tropical forests, there was no solution to tackling climate change. Dr Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change (IPCC), warned that the impacts of climate change could cause havoc in many of the poorest places in the world.

The experts' memorandum called for resources being used to aid economic recovery to put the world on to a path towards a low-carbon economy.