Sir Nicholas Stern has warned that the gloomy predictions of his high-profile review of the future effects of global warming underestimated the risks, and that climate change poses a bigger threat than he realised.
Stern said this week that new scientific findings showed greenhouse gas emissions were causing more damage than was understood in 2006, when he prepared his study for the government. He pointed to last year's reports from the Intergovernmental Panel on Climate Change (IPCC) and new research which shows that the planet's oceans and forests are soaking up less carbon dioxide than expected.
He said: "Emissions are growing much faster than we'd thought, the absorptive capacity of the planet is less than we'd thought, the risks of greenhouse gases are potentially bigger than more cautious estimates and the speed of climate change seems to be faster."
Stern said the new findings vindicated his report, which has been criticised by climate sceptics and some economists as exaggerating the possible damage. "People who said I was scaremongering were profoundly wrong," he told a conference in London.
He said that increasing commitments from countries to curb greenhouse gases now needed to be translated into action. Earlier this week, Rajendra Pachauri, head of the IPCC, said a lack of such action from developed countries could derail attempts to seal a new global climate treaty at a crucial meeting in Copenhagen next year.
The Stern Review was credited with shifting the debate about climate change from an environmental focus to the economic impacts. It said the expected increase in extreme weather, with the associated and expensive problems of agricultural failure, water scarcity, disease and mass migration, meant that global warming could swallow up to 20% of the world's GDP, with the poorest countries the worst affected. The cost of addressing the problem, it said, could be limited to about 1% of GDP, provided it started on a serious scale within 10 to 20 years.
Stern's study was largely based on the previous IPCC report that appeared in 2001. The IPCC raised the stakes last year when it said that steps to curb emissions were needed by 2015 if the worst effects of global warming were to be avoided. Since then, a number of polar experts have warned that the Arctic and Antarctic are losing ice much faster than thought, and that the sea level rise could be more severe than the IPCC suggested. Other studies, focusing on how greenhouse gases are swapped between the land, sea and atmosphere, have suggested that scientists have underestimated the speed and strength with which serious climate change will strike.
Last October, scientists warned that global warming will be "stronger than expected and sooner than expected", after a new analysis showed carbon dioxide is accumulating in the atmosphere much more quickly than predicted. Experts said that the rise was partly down to soaring economic development in China.