Climate change will cost the world's economies $20 trillion (£10.8 trillion) a year by the end of the century unless urgent action is taken to avert disaster, a British environmental pressure group has warned.
Friends of the Earth has said that allowing global warming to continue unchecked would mean a temperature rise of 4 degrees C by 2100, which in turn would cause economic damage worth up to 8 per cent of global GDP.
Its figures come from an analysis of more than 100 scientific and economic papers compiled by the Global Development and Environment Institute at Tufts University in Massachusetts.
It concluded global temperatures are already 0.6 degrees C above pre-industrial levels and temperatures would rise by more than 2 degrees C unless there were "immediate and vigorous efforts to reduce emissions".
A 3 degrees C increase would be "extremely likely without major efforts at reducing emissions" and the increase would be 4 degrees C with "no efforts at reducing emissions".
A 4 degrees C rise, said Friends of the Earth, would mean much hotter summers, droughts, flooding costing £22bn a year by 2080, a doubling of the number of people at risk of coastal flooding to 1.8 million and the need for a cooling system on the London Underground.
London's Thames Barrier would also be unable to cope with the demands on it from rising sea levels.
Friends of the Earth's head of campaigns Mike Childs, said: "This report demonstrates that climate change will not only be an environmental and social disaster, it will also be an economic catastrophe, especially if global temperatures are allowed to increase by more than 2 degrees C."
But there may yet be business opportunities in the grim predictions.
The warning has come at the same time as energy giant Shell has said finding solutions to climate change could create a £30bn market for British businesses over the coming decade.
