· Damage forecast to cost 8% of global GDP by 2100
· UK 'faces droughts and floods costing billions'
GuardianFailure to take action to combat climate change will cause environmental catastrophe and cost the global economy $20 trillion (£10.8 trillion) a year by the end of the century, the pressure group Friends of the Earth says today.
In a report based on research from more than 100 scientific and economic papers, the group says allowing global warming to continue unchecked will mean a temperature rise of 4C by 2100, causing economic damage worth up to 8% of global GDP.
The study coincides with research from the oil group Shell yesterday, which said the need to find solutions to climate change could create a £30bn market for British business over the coming decade.
Shell's chairman, James Smith, said: "We do have to tackle climate change and that's a matter for government, companies and individuals as well, because the costs in the coming years from rising sea levels, from floods and extremes of climate will be too high.
"The cost-benefit equation of action to tackle climate change is favourable. That's true not just for the UK but internationally as well," he said on the BBC Radio 4 Today programme.
Both reports were released ahead of the government's own review of the economics of climate change carried out for the Treasury by Sir Nicholas Stern. That is expected to be published later this month and is likely to conclude that the costs of tackling climate change are far more modest than had been thought.
The Friends of the Earth report was compiled by economists at the Global Development and Environment Institute at Tufts University in Massachusetts in the US. Institute director Frank Ackerman said: "The climate system has enormous momentum, as does the economic system that emits so much carbon dioxide. Like a supertanker, which has to turn off its engines 25km before it comes to a stop, we have to start turning off greenhouse gas emissions now in order to avoid catastrophe in decades to come."
According to the report, global temperatures are already 0.6C above pre-industrial levels and temperatures will rise by more than 2C unless there are "immediate and vigorous efforts to reduce emissions", that a 3C increase was "extremely likely without major efforts at reducing emissions", and the increase would be 4C with "no efforts at reducing emissions".
Friends of the Earth says the impact on Britain of a 4C increase will be much hotter summers, droughts, flooding to cost £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.
It also says there is a danger that the Thames Barrier will 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 2C."
Shell's research sought to quantify for the first time the potential size of the market for businesses that develop technologies, products and services that help combat climate change. There would be a global market worth $1 trillion within five years, it said.