When the Kyoto Protocol, the world's only legally-binding pact to tackle climate change was adopted in the economically-booming 1990s, it was meant to be a down payment.
Sunday's tentative promise, thrashed out over days of talks, that all the big emitters will eventually join an international scheme of carbon reduction targets is the latest small instalment and allows UN law to retain some value in trying to stop the planet from overheating.
Environmentalists want much more.
But persuading major emitters China and India, who were not part of the original Kyoto carbon cuts, and the United States, which signed but did not ratify the Kyoto Protocol, to agree to any kind of a global, legal deal is still a small step previous climate summits failed to manage.
"International targets do two things. They motivate and reinforce national policy and they give confidence to countries and investors that policy will last," said Michael Jacobs, visiting professor on climate change and the environment at the London School of Economics.
"In the end what drives emissions reduction is national policy, not international targets. Durban can only provide the basis for this."
The European Union, which has enshrined Kyoto principles into its own law, led the charge for an agreement that would eventually produce a top-down deal with legal strength, rather than the bottom-up approach as favoured by the United States and others, involving only domestic legislation and voluntary pledges.
"We think you need a multilateral system," said Environment minister Marcin Korolec of Poland, current holder of the EU presidency. He went so far as to compare the success of Sunday's deal with climate talks in 1995, which led to the Kyoto Protocol two years later.
EU Climate Commissioner Connie Hedegaard has repeatedly said the EU's own experience proves top-down, binding targets are the way to guarantee action.
In addition to its commitment under the first phase of the Kyoto Protocol, the European Union has its own set of three 2020 green goals, two of which are binding and one of which is not binding.
It is on track to meet the mandatory goals of a 20% drop in emissions and a 20% rise in renewable energy, but is only expected to half-meet a third, non-binding aim of a 20% improvement in energy efficiency through measures such as insulation and better building design.
The Kyoto Protocol inspired the EU's own legislation and for the treaty's supporters, it can continue to motivate positive change.
Even the extremely lengthy debates, especially in Durban, where the conference broke records in terms of running over time, have intrinsic value.
"Smaller countries have really been the conscience of the conference," said Jason Anderson, head of European climate and energy policy at WWF.
He cited the impact of impassioned pleas from small island nations who fear they could sink under rising sea levels without a strong global pact.
But he also said climate change talks were only one very complex forum for moving to a greener future.
In parallel, a green technology race, driven by business momentum, has accelerated and the business community argues it is far more likely than UN talks to deliver on time.
GREEN TECH RACE
China and the United States, as well as being the two biggest carbon emitters, are at the helm of the contest to adopt greener energy sources.
They had to be heavily-persuaded to agree to any kind of wording in Durban that would imply legally binding carbon emissions cuts, but they have adopted green technology with enthusiasm.
In 2010, China invested $54 billion in low carbon energy technology, compared to the United States' $34 billion, the US Pew Environment Group said.
India, the world's third biggest carbon emitter behind China and the United States, is also nervous that binding emissions targets might hobble its economic growth, but it too has also begun moving towards green development.
It has to tackle issues, including the potentially huge capital investment costs of green energy, which are only cheaper in the long run. And it remains to be seen whether it can catch up with China and the United States.
Equally, internationally binding agreements provide no guarantees of change.
Canada, whose huge deposits of oil sands make it a financial challenge to reduce its carbon emissions growth, was theoretically bound by the first phase of Kyoto, but in practice had made clear it has no intention of meeting its targets.