The survey is the third this year by the UN climate panel after one in February saying it was at least 90 percent certain that mankind was to blame for warming and another on April 6 warning of more hunger, droughts, heatwaves and rising seas.

"We're moving from two very sobering reports to what we can do about climate change. And we can do it," Achim Steiner, the head of the UN Environment Programme, told Reuters of the report by the Intergovernmental Panel on Climate Change (IPCC).

"Having shown us the path towards greater and greater problems the IPCC raises our horizons to where the solutions lie and shows that they are within our grasp," he told Reuters.

The report estimates that stabilising greenhouse gas emissions will cost between 0.2 percent and 3.0 percent of world gross domestic product by 2030, depending on the stiffness of curbs on rising emissions of greenhouse gases.

Under some scenarios, GDP growth might even get a tiny net spur from less pollution and health damage from burning fossil fuels, blamed as the main cause of warming.

The draft says: "There is a significant economic potential for the mitigation of greenhouse gas emissions from all sectors over the coming decades, sufficient to offset growth of global emissions or to reduce emissions below current levels."

The conclusions broadly back those by former World Bank chief economist Nicholas Stern, who estimated last year that costs of acting now to slow warming were about one percent of global output, 5 to 20 percent if the world delayed action.

More than 1,000 amendments have been proposed to the draft 24-page summary for policymakers. Some countries complain that is hard to understand and too laden with scientific jargon.

SOLUTIONS

The report lays out solutions such as capturing and burying emissions from coal-fired power plants, a shift to renewable energies such as solar and wind power, more use of nuclear power, more efficient lighting and insulation of buildings.

But it says that temperatures will rise by at least 2 to 2.4 Celsius (3.6 - 4.2F) above pre-industrial levels even under the most stringent curbs. The European Union says a 2 C rise is a threshold for "dangerous" changes to the climate system.

And the big question is whether governments will act.

"I'm optimistic but I don't think it will be straightforward," Steiner said. "There are still many who don't understand the complexity of the issue and hoping that it will somehow go away."

"The technologies and measures necessary to combat climate change exist already -- all we need is the courage and vision of the political decision-makers," said Stephan Singer of the WWF conservation group.

A vice-chair of the IPCC said last week that it might take more disasters such as Hurricane Katrina that battered New Orleans in 2005 to spur politicians to do more.

"The push for greater mitigation will come through catastrophes and other extreme events," Mohan Munasinghe told Reuters in an interview in Colombo.

A senior delegate to the talks said he expected all countries to be difficult during the week-long discussions.

"The IPCC cannot be policy prescriptive so there are no policy statements in the documents and governments go through and try to make sure there aren't any," said the delegate who did not want to be identified.

This inevitably meant the word-by-word approval process of the final text always created controversy.