The global climate negotiations in Copenhagen produced neither a grand success nor the complete meltdown that seemed almost certain as late as Friday afternoon. Despite two years of advance work, the meeting failed to convert a rare gathering of world leaders into an ambitious, legally binding action plan for reducing greenhouse gas emissions. It produced instead a softer interim accord that, at least in principle, would curb greenhouses gases, provide ways to verify countries’ emissions, save rain forests, shield vulnerable nations from the impacts of climate change, and share the costs.

The hard work has only begun, in Washington and elsewhere. But Copenhagen’s achievements are not trivial, given the complexity of the issue and the differences among rich and poor countries. President Obama deserves much of the credit. He arrived as the talks were collapsing, spent 13 hours in nonstop negotiations and played hardball with the Chinese. With time running out — and with the help of China, India, Brazil and South Africa — he forged an agreement that all but a handful of the 193 nations on hand accepted.

Mr. Obama aside, there were two keys to the deal. One was a dramatic offer of $100 billion in aid from the industrialized nations to poorer countries to help them move to less-polluting sources of energy and to deal with drought and other consequences of warming. The offer had an instant soothing effect on many poorer nations that had been threatening to walk out all week.

The other was China’s willingness to submit to a verification system under which all countries would agree to report on their actions and — assuming details could be worked out — open their books to inspection. Transparency is a huge issue in Congress, and Mr. Obama made clear in his opening remarks on Friday that he would not agree to a deal unless China gave ground.

An enormous amount of work lies ahead, both for the president and for the other signatories to what is now being called the Copenhagen Accord. In order to deliver on his promises to reduce America’s greenhouse gas emissions by 17 percent by 2020 and provide a chunk of that $100 billion in aid, Mr. Obama must persuade the Senate to approve a cap-and-trade bill — a huge task.

Meanwhile, there can be no letup by the rest of the world’s negotiators, no matter how tired and beat up they may be. These talks have been so chaotic and contentious that some people believe the United Nations machinery has outlived its usefulness, and real progress will henceforth be made in smaller gatherings of the big players.

There may be some truth to this, but at the moment it is hard to see how many of the arrangements agreed to in principle at Copenhagen — the verification system, for instance — can be made to work without detailed agreements. There must also be some mechanism that holds all countries responsible for doing everything they can to tackle climate change. As it is, the pledges now on the table, from both rich and poor countries, are nowhere near enough to keep atmospheric concentrations of carbon dioxide from rising above dangerous levels.

But for the moment it is worth savoring the steps forward. China is now a player in the effort to combat climate change in a way it has never been, putting measurable emissions reductions targets on the table and accepting verification. And the United States is very much back in the game too. After eight years of playing the spoiler, it is now a leader with a president who seems to embrace the role.