The U.N. conference in Doha has yielded no progress on curbing greenhouse emissions, with many climate change delegates in despair.
As thousands of delegates left Doha, some asked whether the U.N. system even made matters worse by providing cover for leaders to take no meaningful action.
Supporters say the U.N. process is still the only framework for global action.
The United Nations also plays an essential role as the "central bank" for carbon trading schemes, such as the one set up by the European Union.
But unless rich and poor countries can inject urgency into their negotiations, they are heading for a diplomatic fiasco in 2015 - their next deadline for a new global deal.
"Much much more is needed if we are to save this process from being simply a process for the sake of process, a process that simply provides for talk and no action, a process that locks in the death of our nations, our people, and our children," said Kieren Keke, foreign minister of Nauru, who fears his Pacific island state could become uninhabitable.
The conference held in Qatar - the country that produces the largest per-capita volume of greenhouse gases in the world - agreed to extend the emissions-limiting Kyoto Protocol, which would have run out within weeks.
But Canada, Russia and Japan - where the protocol was signed 15 years ago - all abandoned the agreement.
The United States never ratified it in the first place, and it excludes developing countries where emissions are growing most quickly.
Delegates flew home from Doha without securing a single new pledge to cut pollution from a major emitter.
So far, U.N. climate talks have missed just about every deadline.
The rich nations of the world promised two decades ago to halt their rise in greenhouse gases. They failed. Next, they promised a sequel to Kyoto by 2009. They failed again.
Now they have a 2015 deadline to get a new global, binding deal in place, to enter into force after the extension of Kyoto expires in 2020.
For the first time, it would apply to rich and poor countries alike.
But with the world's nations divided over who must pay the cost, the task of reaching accord seems beyond the capabilities of the vast corps of international delegates.
Meanwhile, the world's weather is only getting more unstable.
As the Doha talks dragged on, Typhoon Bopha in the Philippines left nearly 1,000 people dead or missing.
Hurricane Sandy last month was a reminder that even rich countries are not safe from extreme weather, which scientists say will become ever more common as the world heats up.
A series of reports released during the Doha talks said the world faced the prospect of 4 degrees Celsius (7.2F) of warming, rather than the 2 degree (3.6F) limit that nations adopted in 2010 as a maximum to avoid dangerous changes.
According to the World Bank, that would mean food and water shortages, habitats wiped out, coastal communities wrecked by rising seas, deserts spreading, and droughts both more frequent and severe.
Most impact would be borne by the world's poorest.
"The alarm bells are going off all over the place," Alden Meyer, of the Union of Concerned Scientists, said.
"We are in a crisis and treating it like a process where we can dither away forever."
Action at ground level has had a positive impact, even as the U.N. dithers.
Investment in carbon-free renewable energy hit a record $260 billion in 2011.
In the United States, the discovery of techniques to produce natural gas from shale has cut the cost of gas, which has reduced emissions from the world's biggest polluter by replacing coal, a bigger carbon emitter, for power generation.
But although U.S. emissions - nearly a quarter of the world's total - have fallen, for the world as a whole this year they are expected to rise by 2.6 per cent, up by 58 per cent since 1990.
Emerging economies led by China and India account for most of the growth.
Although frustrated by days and nights of haggling, ministers still back the United Nations as part of the solution.
"It's clear to me that this process is the only global framework we have and since this is a global problem, it has to be addressed globally," Denmark's Energy Minister Martin Lidegaard said.
"But obviously, this can't stand alone. Nations can't continue to hide behind the process. There's a direct link between what we deliver at home and here.
"We desperately need to combine action by regions, municipalities, citizens with this global approach. That is becoming more and more evident."
Negotiators say ultimately politicians - distracted by other events - need to become engaged.
"It (the environment) is no longer on the front page with the political and financial crisis. That is the reason why heads of state have to turn to this," the European Union's chief negotiator Artur Runge-Metzger said.
The conference is an easy target for cynics - not least because it was held in Qatar, a desert kingdom that exports carbon-producing fossil fuel and uses the proceeds to fund a lavish lifestyle for many of its 2.5 million people.
A country that burns fuel to desalinate water and build golf courses in the desert seems like an odd place to talk about curtailing consumption.
But supporters say bringing producers like Qatar into the consensus for change is a step forward.
Business leaders are also getting involved.
"A lot of CEOs from the region have turned up. A lot of them are talking about sustainability and resource efficiency. That's no longer a dirty word," said Russel Mills, global director for energy and climate policy at Dow Chemical Co.
Dow, like many other big industrial firms, keeps a close eye on U.N. carbon policy because of the United Nations' role as "a kind of central bank" for pollution allowances.
The most developed carbon trading scheme is the European Union's, which has lurched from crisis to crisis.
The value of EU Emissions Trading Scheme permits sank to a record low this month under the burden of surplus allowances during a recession.
But other jurisdictions such as Australia, California, South Korea and even China believe they can learn from Europe's mistakes and are developing their own emissions trading.
Such schemes could be the planet's best hope of survival, and the United Nations is likely to play a role.
"Economy-wide carbon pricing, whether carbon taxes or cap and trade, is the only approach that can conceivably achieve the targets scientists advocate," Robert Stavins, a professor of business and government at Harvard in the United States, said.
"Also, it will be most the cost-effective and therefore in the long run the most politically-viable approach."
Still, even with the best of intentions, U.N. diplomats are unlikely ever to deliver change at the pace scientists seek.
"Science is demanding immediate and drastic action," Christiana Figueres, head of the U.N. Climate Change Secretariat, said.
"Policy, economics and financing cannot move in drastic fashion."