At the end it turned out to be what had been apprehended all along. Copenhagen was much ado about nothing. The final accord acknowledges the need to keep temperature rises to no more than 2C, but there is no commitment from anyone to emission reduction to achieve that lofty goal.
President Barack Obama hailed it as an "unprecedented breakthrough," but conceded in the same breath, "This progress is not enough."
Before leaving Copenhagen, he hoped whatever had been agreed upon would be the starting gun for a much stronger effort to combat global warming.
"Today we have made a meaningful and unprecedented breakthrough here in Copenhagen," Obama told reporters.
"For the first time in history, all major economies have come together to accept their responsibility to take action to confront the threat of climate change."
He added: "Going forward, we are going to have to build on the momentum we have achieved here in Copenhagen. We have come a long way but we have much further to go."
The agreement set a commitment to limit global warming to two degrees Celsius (3.6 Fahrenheit), but did not spell out the important stepping stones -- global emissions targets for 2020 or 2050 -- for getting there.
Nor did it spell out a year by which emissions should peak, a demand made by rich countries that was fiercely opposed by China, or insist on tough compliance mechanisms to ensure nations honoured their promises.
Somewhat more successfully, it spelt out some details for how poor countries should be financially aided to shore up their defences against rising seas, water stress, floods and storms.
Rich countries pledged to commit 30 billion dollars in "short-track" finance for the 2010-2012 period, including 11 billion from Japan, 10.6 billion from the European Union and 3.6 billion dollars from the United States.
They held up a goal of "jointly mobilising" 100 billion dollars by 2020, although details were sketchy.
The agreement set up a forestry deal which is hoped would significantly reduce deforestation in return for cash. It lacked the kind of independent verification of emission reductions by developing countries that the US and others demanded.
Many observers blamed the US for coming to the talks with an offer of just 4% emissions cuts on 1990 levels. The final text made no obligations on developing countries to make cuts.
Negotiators will now work on individual agreements such as forests, technology, and finance - but, without strong leadership, the chances are that it will take years to complete.
"The agreement is not perfect but it's the best one possible," French President Nicolas Sarkozy told reporters, adding that another global warming summit would be hosted by Germany in mid-2010.
German Chancellor Angela Merkel admitted she viewed the result "with mixed emotions" but added that "the only alternative to the agreement would have been a failure."
The deal was hammered out in talks between Obama and the leaders of China, India, Brazil and South Africa as well as key European countries, diplomats said.
Australian Prime Minister Kevin Rudd said that talks had been close to collapse on seven occasions, but were ultimately saved by sharp deal-making in which Obama played a lead role.
China had bristled at anything called "verification" of its plan to cut the intensity of its carbon emissions, seeing it as an infringement of sovereignty and saying that rich nations bore primary responsibility for global warming.
Disagreements between the China and United States -- the world's No. 1 and 2 carbon polluters -- had been at the core of the divisions holding up a deal.
The emergence of a deal came at the end of a day in which several draft agreements were knocked back, with leaders themselves taking over the task of redrafting the exact wording of three pages of text.
Hours after Obama and other key leaders flew home, delegates from 194 nations gathered to approve the text and there was a raucous response from several developing states that resented not being part of the closed-door discussions.
Venezuela's representative Claudia Salerno Caldera held up what appeared to be a bloody palm, saying that she had cut her hand in an effort to gain the attention of conference chair Denmark.
"You are going to endorse this coup d'etat against the United Nations," she said as an all-night session approached dawn on its 13th day.
Ian Fry of Tuvalu, a tiny Pacific island whose very existence is threatened by climate change, said the agreement amounted to Biblical betrayal and vowed to defeat it.Related article: Climate deal 'worst in history': G77
"It looks like we are being offered 30 pieces of silver to betray our people and our future," he said to applause in the chamber.
John Sauven, executive director of Greenpeace UK, said: "The city of Copenhagen is a crime scene tonight, with the guilty men and women fleeing to the airport. Ed Miliband [UK climate change secretary] is among the very few that come out of this summit with any credit. It is now evident that beating global warming will require a radically different model of politics than the one on display here in Copenhagen."
Lydia Baker, Save the Children's policy adviser said: "By signing a sub-standard deal, world leaders have effectively signed a death warrant for many of the world's poorest children. Up to 250,000 children from poor communities could die before the next major meeting in Mexico at the end of next year."