A group of former leaders and climate experts said the annual U.N. COP climate talks were no longer fit for purpose and needed to be reformed, publishing a critical open letter mid-way through what has so far been a fractious summit.
Nearly 200 countries are gathered in Baku, Azerbaijan with a primary goal of agreeing a new target for how much money needs to be provided to help developing countries adapt to climate change and recover from destructive weather.
So far those talks have made little progress.
Delegates struggled for hours on the opening day to agree an agenda and the mood has been soured by doubts about the United States' future role under a Donald Trump presidency, diplomatic spats involving the host nation and the withdrawal of the Argentinian delegation.
Friday's letter, signed by more than 20 experts, former leaders and scientists, including former UNFCCC boss Christiana Figueres and former U.N. Secretary-General Ban Ki-moon, said the COP process had achieved much, but now needed an overhaul.
"It is now clear that the COP is no longer fit for purpose. Its current structure simply cannot deliver the change at exponential speed and scale, which is essential to ensure a safe climate landing for humanity," the letter said.
"This is what compels our call for a fundamental overhaul of the COP. We need a shift from negotiation to implementation, enabling the COP to deliver on agreed commitments and ensure the urgent energy transition and phase-out of fossil energy."
Figueres later said some of the ideas in the letter had been misinterpreted.
"The COP process is an essential and irreplaceable vehicle for supporting the multilateral, multisectoral, systemic change we urgently need. Now more than ever," she said in a post on LinkedIn.
Nevertheless, others have also criticised the COP process in Baku.
Earlier this week Barbados Prime Minister Mia Mottley called for urgent reform and Albanian Prime Minister Edi Rama spoke of leaders sitting on sofas and taking photographs while speeches at the summit played out on muted television screens.
Asked about the letter and the overall process, the COP29 Presidency's Lead Negotiator Yalchin Rafiyev said: "The process has already delivered ... so far by reducing the projected warming, delivering finance to those in need - and it's better than any alternative."
However he said the multilateral process was under pressure and that COP29 would be "a litmus test for the global climate architecture."
