Negotiators from 181 countries began work on the first draft of a new global warming treaty Monday, calling it a good beginning despite complaints it was unbalanced and incomplete.
Delegates have been brainstorming and arguing over principles for 18 months.
The draft includes conflicting proposals pointing to tough negotiations ahead. Among dozens of unresolved issues was whether developing economies must commit to control their greenhouse gas emissions and whether their commitments would be legally binding or voluntary.
The U.S. delegation wanted the text to put all countries on a more equal footing, requiring every country to take action to fight climate change according to its capability.
Developing countries said the draft failed to take adequate account of their proposals.
U.N. scientists warn that unrestrained emissions of greenhouse gases, mainly from fossil fuels from heavy industry and vehicles, will lead to changes in temperatures and rainfall, putting millions of people at risk of more severe droughts and storms, rising sea levels that could flood coastlines and sink entire islands, cause the extinction of plant and animal species and increase health hazards for man.
Michael Zammit Cutajar, who compiled the draft from dozens of position papers submitted by countries, acknowledged it was "complex" and "messy," but said he was pleased with the initial reception.
The draft "represents a significant new step in the talks," said Yvo de Boer, executive secretary of the U.N. Framework Convention on Climate Change.
The documents present a range of options on core issues: how much industrial countries must cut carbon emissions; how to raise the tens of billions of dollars needed annually for developing countries to adapt to climate change like shifts in agriculture or coastal erosion due to rising sea levels; and how to compensate tropical countries for slowing the destruction of the rain forests, either from an established fund or from selling credits on the carbon market for avoiding deforestation.
Countries were expected to make more additions to the draft before beginning the arduous task of cutting deals, weeding out proposals and sharpening the text into a consensus document.
Four more negotiating conferences were scheduled for this year, culminating in Copenhagen, Denmark, in December when the agreement is due to be adopted.
But the hard political decisions were likely to be taken at top-level meetings outside the U.N. framework. Heads of state are due to confer on climate issues at least four times before the Copenhagen conference.
"The signals have to come from above to start the process," said environmental activist Jennifer Morgan of the E3G think tank.
Developing countries with rapidly expanding economies like China and India have pledged to curb the growth of their carbon emissions, in exchange for funding and green technologies from the industrial countries. They say the level of funding would determine the commitments they would take on in the Copenhagen agreement.
The European Union indicated it was unlikely to come up with specific figures to contribute to a climate change fund before Copenhagen.
De Boer said the developing countries needed clarity on the financial support they will get, "so I hope that much of the discussion will take place as early as possible before Copenhagen,"
The Copenhagen agreement would succeed and expand on the 1997 Kyoto Protocol, which required 37 industrial nations to cut emissions blamed for global warming by a total of 5 percent by 1990, but which made no obligations on any other country.
The United States rejected the Kyoto deal, partly because it excluded developing economies. Reversing that policy, the administration of President Barack Obama has pledged to take a leading role in crafting the next climate deal.