By Alister Doyle, Environment Correspondent
PARIS (Reuters) - The U.N. climate panel is set to issue its strongest warning yet on Friday that human activities are causing a damaging global warming likely to bring more heatwaves, droughts and rising seas.
The group, the most authoritative on climate change with 2,500 scientists from 130 countries, is also due to say that oceans will keep rising for more than 1,000 years even if governments stabilise greenhouse gas emissions this century.
Scientists and government officials in the Intergovernmental Panel on Climate Change (IPCC) have been meeting in Paris since Monday to review the report, including a 15-page summary for policymakers.
"The talks are moving forward," one IPCC official said. The IPCC says it will publish the results on Friday at 0830 GMT.
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The report, increasing certainty that humans are to blame for warming, may put pressure on governments and companies to do more to curb a build-up of greenhouse gases mainly from burning fossil fuels in power plants, factories and cars.
"It is very likely that (human) greenhouse gases caused most of the observed increase in globally averaged temperatures since the mid-20th century," according to a final draft.
"Very likely" means a probability of at least 90 percent -- up from a judgement of "likely", or a 66 percent probability, in the previous 2001 report. The report is the first of four this year by the panel that will outline threats of warming.
The Paris study, looking at the science of global warming, will also project a "best estimate" that temperatures will rise by 3 Celsius (5.4 Fahrenheit) by 2100 over pre-industrial levels, the biggest change in a century for thousands of years.
ICE AGE
It says bigger gains, of up to 6.3C in one model, cannot be ruled out but do not fit well with other data. The world is now about 5C warmer than during the last Ice Age.
The draft projects that Arctic ice will shrink, and perhaps disappear in summers by 2100, while heatwaves and downpours would get more frequent. The numbers of tropical hurricanes and typhoons might decrease but the storms would become stronger.
The Gulf Stream bringing warm waters to the North Atlantic could slow, although a shutdown is highly unlikely, it says.
And sea levels are likely to rise by between 28 and 43 cms (11-17 inches) this century, a lower range than forecast in 2001. Rising seas threaten low-lying Pacific islands and low-lying coastal nations from Bangladesh to the Netherlands.
"Governments planning coastal defences have to live with large uncertainties for now, and quite some time in future," said Stefan Rahmstorf of Germany’s Potsdam Institute for Climate Impact Research.
Rahmstorf wrote a report last year saying that observations of past changes indicated a bigger rise by 2100, of 50-140 cms.
The Eiffel Tower in Paris, near where the IPCC experts were meeting, was to shut off its famous night-time illuminations for five minutes on Thursday night to draw attention to energy use.
U.N. officials hope the IPCC report will spur stalled talks on expanding the fight against global warming.
Thirty five industrial nations aim to cut emissions of greenhouse gases to five percent below 1990 levels by 2008-12 under the U.N.’s Kyoto Protocol and want outsiders such as the United States, China and India to do more.
Last week President George W. Bush said climate change was a "serious challenge". But he has stopped short of capping emissions despite pressure from Democrats who control both houses of Congress -- arguing Kyoto would damage the economy.
