Ministers will review the UN's 1994 climate change convention, signed by ex-US President George Bush, and its goal of limiting greenhouse gases to levels "that would prevent dangerous (human) interference with the climate system."

"You can ask the question of whether changes we have already observed are dangerous," said Rajendra Pachauri, chairman of the UN's Intergovernmental Panel on Climate Change. "It will be a political decision".

The 1990s were probably the warmest decade in a millennium and 1998 the warmest year on record, according to UN data. The Kyoto protocol on curbing global warming, due to enter into force on Feb. 16, is the main spinoff of the convention.

An eight-nation report last month showed the Arctic is warming at double the rate of the rest of the globe, threatening livelihoods of indigenous hunters and perhaps driving polar bears to extinction in the wild.

Indigenous groups say the changes are obviously dangerous and, like many governments, say that much deeper cuts in emissions of greenhouse gases from burning fossil fuels will be needed when Kyoto runs out in 2012.

"I don't know if it's dangerous but it's out of the pathway the rest of the planet is taking by a factor of two," said Robert Corell, who led the study by 250 scientists.

Another report this week in the journal Nature said that human activities, notably the burning of fossil fuels from cars to power plants, had raised risks of heatwaves like one in Europe in 2003 in which more than 20,000 people died.

LIMIT RISES

The senior US climate negotiator, Harlan Watson, said there was insufficient grounds yet to define "dangerous". "The bulk of the scientific opinion is we just don't know enough to be able to predict impact," he said.

But some want to draw a line in the sand.

The European Union and some environmental groups want to limit any global temperature rise to 2.0 Celsius (3.6F). Temperatures have risen by 0.6C since the late 1800s.

Alternatively, Pachauri said that nations could set a limit for concentrations of heat-trapping carbon dioxide in the atmosphere, which have risen by about 30 percent since the start of the industrial revolution.

President George W. Bush pulled out in 2001 from the 128-nation Kyoto protocol, which seeks to cut greenhouse gas emissions by five percent from 1990 levels by 2012. Bush argued it was too expensive and wrongly excluded developing nations.

And the United States says it has no plans to rejoin the UN efforts.

Even so, Bush is not the only one failing under Kyoto. Carbon dioxide emissions by rich nations involved in Kyoto are running 8.4 percent over 1990 levels, environmental group WWF said.