Some delegates expressed pessimism over a breakthrough ahead of a crucial summit in Copenhagen in December, at which global leaders are expected to agree on a successor to the 1997 Kyoto protocol. Environmental campaigners said another "talk shop" at a final preparatory meeting next month in Barcelona risked a complete collapse.
But other observers argued that this week's rancorous debate over the responsibility of rich and poor nations to curb emissions was part of a complex negotiating process that was still largely on track.
Poorer countries griped that rich countries hadn't pledged adequate funding for dealing with the impact of climate change. Nonetheless, UN officials said that the talks involving 180 nations had made progress and that thorny details could still be resolved, provided there was enough political will. "All the ingredients of success are on the table. What we must do now is step back from self-interest and let common interest prevail," UN climate chief Yvo de Boer told a press conference.
A bloc of developing countries erupted in fury after European delegates proposed a reworking of Kyoto, a move that critics said was an attempt to kill the treaty. European Union officials denied trying to destroy it and pointed out that the bloc was meeting its Kyoto commitments on emissions and was ready to make further cuts, provided other polluters signed on. The Copenhagen meeting is designed to set new targets for 37 developed countries bound by Kyoto and to lay out the obligations of those not covered by it, including the US, China and India.
The dispute over Europe's stance appeared to nudge the US, typically the villain at such events, out of the spotlight. The US declined to ratify Kyoto on the grounds that it omitted China and other major polluters, a position that hardened under the Bush administration. US President Barack Obama has taken a different tack, saying emission cuts were unavoidable and championing the economic upside of green energy.
The US Congress is currently deliberating bills that would reduce emissions by between 17 and 20 percent by 2020. UN climate officials have warned that the legislation may not be passed in time for the December meeting in Copenhagen, making it harder to agree on universal targets.
Jonathan Pershing, the US negotiator, told reporters that Congress was working hard to meet this deadline but said that if it didn't then it would be "extraordinarily difficult for the US to commit to a specific number" in Copenhagen.
However, Mr. de Boer argued that this wouldn't be a deal breaker. "I don't believe that (the US) legislation has to be finalized for the US to sign up to an agreement in Copenhagen," he said.
Lumumba di-Apinge, a Sudanese delegate and spokesman for the G77 group of developing countries, told reporters that rich nations that had polluted the planet must do more to soften the blow to poor countries, including paying for clean energy projects. "Developed countries refused to put forward any serious commitments necessary (for poorer countries) to achieve the transition… to a low carbon-emission economy," he said. The World Bank has estimated that developing countries would need as much as $100 billion annually until 2050 to spend on adaptation to warmer conditions and more extreme weather events. This amount is double the current level of aid given by rich countries.