WASHINGTON: Human-fuelled global warming has reached a "tipping point," according to a new survey of scientific research that found warming would continue even if greenhouse gas emissions halted immediately.

"It would keep on warming even though we have stopped the cause, which is greenhouse gases from the combustion of fossil fuels," David Jhirad of the Washington-based World Resources Institute said on Wednesday.

The rate of warming would be slower, Jhirad said in a telephone interview, but a kind of thermal inertia would ensure that global temperatures continue their upward trend.

He referred to a report released by the non-profit institute this week that analyzed research reports on climate change for 2005.

"Taken collectively, they suggest that the world may well have moved past a key physical tipping point," the institute wrote.

Jhirad said there were actually two tipping points. The first is that there is no doubt human activities cause global warming; a more physical tipping point is that the effects of global warming are evident now.

The report, based on research published in journals including Science and Nature, also found the effects of climate change were so severe they should spur urgent action to prevent more damage and to combat damage that has already occurred.

"We can't assume this change is so far in the future that we can afford to delay," Jhirad said.

The World Resources Institute, founded in 1982, is a non-partisan environmental think tank that works with industry and other ecological groups around the world.

New policies should encourage companies to make technological and commercial innovations that will cut air pollution, Jhirad said, adding US companies were also clamouring for political leadership.

Jhirad said he was "underwhelmed" by US political leadership on this issue. In 2001, President George W. Bush pulled the United States out of the Kyoto Protocol, the United Nations' main plan to curb global warming. He denounced Kyoto as an economic straitjacket that would cost US jobs and said it wrongly excluded developing nations.

The Kyoto agreement obliges some 40 industrial nations to cut emissions of heat-trapping gases by 5.2 per cent below 1990 levels by 2008 to 2012.

Jhirad said the United States should adopt a system of carbon trading, like one in place in much of Europe, where companies that emit few greenhouse gases get credits that can be traded with companies that emit a lot.

Source: China Daily