Rich nations must commit to more ambitious targets for slashing greenhouse gases by 2020 in order to kickstart a new deal on global warming, the top UN climate official said last Wednesday.
"More ambition is clearly needed on the part of industrialised countries if we are to get a robust response to climate change," Yvo de Boer said at a webcast news conference on the final day of a negotiation round under the UN Framework Convention on Climate Change (UNFCCC).
More than 190 nations have set themselves an end-of-year deadline to hammer out a new climate treaty, to take effect from the end of 2012 when provisions of the Kyoto Protocol run out.
The 11-day meeting in Bonn was the first in a series this year - and the first to be attended by US President Barack Obama's administration - in the run-up to the climate summit in Copenhagen in December.
Citing the UN's Intergovernmental Panel on Climate Change (IPCC), de Boer said rich nations must aim for carbon pollution cuts between 25 and 40 per cent by 2020 compared with 1990 levels.
"The numbers that have been discussed so far are still a significant distance from that range," he said.
In Bonn, many developing nations - which will be hit first and hardest by impacts ranging from rising sea levels to drought and extreme weather - put forward a proposal calling for Europe, the US, Japan and other advanced economies to cut emissions by at least 40 per cent.
De Boer seemed to acknowledge that even a 25 per cent reduction might be hard to reach, describing the IPCC's targeted range as a "guiding light" that negotiators should be "working toward".
Industrialised nations are prepared to take on the larger burden, but want emerging economies that are carbon polluters - such as China, India and Brazil - to undertake action of some kind.
These countries, in turn, say rich nations should take the lead in making deep cuts, and put money on the table to help them develop clean technology and adapt to climate change already underway.
Obama's entry into a process riven by deep divisions generated huge expectations after George W. Bush, who rejected Kyoto and nearly torpedoed the 2007 Bali agreement that set the negotiation path towards a new climate treaty.
Scrapping the bulk of Bush's policies, Obama has said the US will restore greenhouse gases to 1990 levels by 2020 and use a cap-and-trade system to achieve that goal.
While welcoming this change, some delegates have said the target still compares poorly with Europe's pledge to cut its own emissions by at least 20 per cent by that date, and 30 per cent if other advanced economies follow suit.
Another worry has been that the US target has yet to be backed by Congress and has not been officially put on the UNFCCC table.
"The other industrialised countries... are very, very nervous in coming forward with concrete numbers without knowing what the US will come forward with," said Harald Dovland, who chaired one of the two main negotiating groups.
Green groups said the Bonn talks had gone nowhere.
"The diplomats and negotiators in Bonn have been treading water for two weeks," said Greenpeace International's Stephanie Tunmore.
"As things stand, this exact same meeting will be repeated in June. Heads of state need to give these talks some urgently-needed leadership and direction if we are to avert catastrophic climate change."
World Wildlife Fund's Kim Carstensen said leaders of rich countries urgently had to put a climate deal on "their personal agenda".
"Stringent targets for emission cuts will be the heart of the new global deal and finance for technology and adaptation (to the impacts of climate change) is the lifeblood," said Carsten. "But the heart is not beating and the blood is not flowing."