COP29 was supposed to offer the stage from which the world’s richest nations finally stepped up to the plate, as far as meeting their historic responsibilities on climate finance. And nine years after the Paris Agreement — and after months of multilateral diplomacy and two weeks of tough talk in Baku — a deal was finally announced. The industrialised nations pledged to pay $300 billion (or £240 billion) annually by 2035 to help poorer countries tackle the impact of climate change. This, we are told, when combined with further contributions by the private sector, represents an eye-watering total of $1.3 trillion.

Predictably, the talks overran: the summit was due to end last Friday, but the agreement was not announced until early on Sunday morning. Just as predictably, objections came in thick and fast. The deal was described variously as “a paltry sum”, “a joke”, “an optical illusion”, and “a betrayal”. The Indian delegation expressed outrage that their objections had been ignored. Campaigners criticised the package, on the grounds that, if finance was supplied in the form of loans, this would add to already high levels of debt stress. And then there is the matter of inflation: generous as it sounds, $300 billion may turn out to be worth less, in real terms, than the previous goal of $100 billion, which was set in 2009 and delivered in 2022.

There were some successes: a common goal among the negotiators in Baku was to prevent a second Donald Trump presidency from undermining years of careful climate discussions, and the 2035 deadline will enable the US to re-engage once Mr Trump leaves office. Similarly, efforts were made to broaden the base of contributors to the global climate cause: bringing China into the conversation was a positive step. The deal wouldn’t please everyone, Mukhtar Babayev, the president of Cop29, wrote in The Guardian on Monday, but it was a significant step forward from the $100 billion pledged in Paris in 2015. “There was a deal at COP29 because the people of the world demanded one and in the end politicians of all countries in their own way, though faced with their own limitations, did the best they could to deliver it.”

In the end, success or failure of the agreement will be judged only by delivery. Promises alone are not enough: as far back as the Kyoto Protocol in 1992, pledges have been made that have not been fulfilled, because there are no credible mechanisms for implementation. It is unclear that there are any institutional safeguards in place to guarantee that the $300 billion promised in Baku will ever be paid. And will the private sector really come up with the promised $1 trillion? Voluntary contributions by governments and the private sector are never going to be enough: even the most eager coalitions of the willing tend to melt away when the pressure is on. True progress will be possible only when governments are legally required to act. The habitability of the planet depends on collective action.