However, the studyīs author, Nicholas Stern, said the outcome is not inevitable.
"The conclusion of the review is essentially optimistic," said Stern, head of the Britainīs Government Economic Service and a former World Bank chief economist. "There is still time to avoid the worst impacts of climate change, if we act now and act internationally."
However, delaying action by a decade could prove dangerous, Stern said. "We must not let this window of opportunity close," he said.
Sternīs report concludes that the costs of global climate change could equal 20 percent of the worldīs gross domestic product or more. In contrast, the costs of action to reduce greenhouse gas emissions to avoid the worst of the impacts could be limited to only about 1 percent of GDP per year, he said.
He said tackling climate change today would be a pro-growth strategy, while ignoring it would ultimately undermine economic growth.
Stern called for a three-pronged approach: Adopting a global carbon taxation or emission trading system, developing technology to reduce carbon emissions, and removing barriers to energy efficiency while educating the public about how they can respond to climate change threats.
The National Environmental Trust and other U.S. environmental advocacy groups endorsed the report, saying it should help persuade the public that preventive measures need to be adopted immediately.
"The 10 to 20 percent projected drop in economic output the report projects would cut about $5,000 to $25,000 a year from the average American familyīs income," NET President Philip Clapp said. "Thatīs a drop of $350 to $700 a month."
However, conservative groups, including the Competitive Enterprise Institute, dismissed the British study as "deeply flawed," particularly the cost estimates.
"The reportīs estimates for reducing greenhouse gas emissions are laughably rosy, while the assumptions about the impacts of global warming are ridiculously overblown," said Myron Ebell, director of energy and global warming policy for the institute.
The full report is available online at
www.hm-treasury.gov.uk . Look
for the Stern Review.