The UN climate summit reached a weak outline of a global agreement in Copenhagen tonight, falling far short of what Britain and many poor countries were seeking and leaving months of tough negotiations to come.

After eight draft texts and all-day talks between 115 world leaders, it was left to Barack Obama and Wen Jiabao, the Chinese premier, to broker a political agreement. The so-called Copenhagen accord "recognises" the scientific case for keeping temperature rises to no more than 2C but does not contain commitments to emissions reductions to achieve that goal.

American officials spun the deal as a "meaningful agreement", but even Obama said: "This progress is not enough."

"We have come a long way, but we have much further to go," he added.

Gordon Brown hailed the night as a success on five out of six measures.

In a press conference held after the talks broke up, Brown said the agreement was a "vital first step" and accepted there was a lot more work to do to get assurances it would become a legally binding agreement. He declined to call it a "historic" conference: "This is the first step we are taking towards a green and low carbon future for the world, steps we are taking together. But like all first steps, the steps are difficult and they are hard."

"I know what we really need is a legally binding treaty as quickly as possible."

The deal was brokered between China, South Africa, India, Brazil and the US, but late last night it was unclear whether it would be adopted by all 192 countries in the full plenary session. The deal aims to provide $30bn a year for poor countries to adapt to climate change from next year to 2012, and $100bn a year by 2020.

But it disappointed African and other vulnerable countries which had been holding out for deeper emission cuts to hold the global temperature rise to 1.5C this century. As widely expected, all references to 1.5C in past drafts were removed at the last minute, but more surprisingly, the earlier 2050 goal of reducing global CO 2 emissions by 80% was also dropped.

The agreement also 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.

Obama hinted that China was to blame for the lack of a substantial deal. In a press conference he condemned the insistence of some countries to look backwards to previous environmental agreements. He said developing countries should be "getting out of that mindset, and moving towards the position where everybody recognises that we all need to move together".

This was a not-so-veiled reference to the row over whether to ditch the Kyoto protocol and its legal distinction between developed and developing countries. Developing nations saw this as an attempt by the rich world to wriggle out of its responsibility for climate change. 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.

Obama cast his trip as a sign of renewed US global leadership: "The time has come for us to get off the sidelines and shape the future that we seek; that is why I came to Copenhagen."

But the US president also said he would not be staying for the final vote "because of weather constraints in Washington".

Lumumba Di-Aping, chief negotiator for the G77 group of 130 developing countries, said the deal had "the lowest level of ambition you can imagine. It's nothing short of climate change scepticism in action. It locks countries into a cycle of poverty for ever. Obama has eliminated any difference between him and Bush."

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 of Save the Children said world leaders had "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."