The world must use its first climate change talks since the Cop28 summit to make "serious progress" on raising the vast sums of money needed to tackle the issue, diplomats were told on Monday.
Simon Stiell, head of the UN Framework Convention on Climate Change, said countries "cannot afford to stumble" during two weeks of talks in Bonn, Germany.
The meeting at the UN climate headquarters marks the halfway point between Cop28, which was hosted the UAE, and the Cop29 talks in Azerbaijan this year.
The summit in Dubai produced the UAE Consensus, in which countries agreed to "transition away" from fossil fuels. Meeting the financial costs involved is expected to be a key theme of the talks in Azerbaijan in November.
A new finance pledge is on the agenda, with the funds to replace the $100 billion rich countries failed to provide by 2020 under a previous agreement.
Figures announced by the Organisation for Economic Co-operation and Development last week showed the target was met in 2022.
"We must make serious progress on finance, the great enabler of climate action," Mr Stiell said in an opening speech in Bonn. "I urge you to move from zero-draft to real options for a new collective quantified goal on climate finance.
"We cannot afford to reach Baku with too much work still to do. So, please, make every hour here count."
Trillion-dollar question
The cost of going green for developing countries is estimated to reach about $6 trillion over the next six years. That is in addition to the costs of preparing for extreme weather, including establishing flood defences and focusing on drought-resistant crops.
Vulnerable countries tend to use UN talks to argue they should not bear the costs when the developed world is mostly responsible for increasing global temperatures.
But rich nations want more countries to chip in than was envisaged when UN climate procedures were drawn up in the 1990s.
The UAE was praised for widening the donor base by contributing $100 million to a climate disaster fund set up at Cop28.
Mr Stiell said the new finance goal must involve grants or cheap loans, rather than adding to debt problems in poorer countries. He added that the money should partly come from "new and innovative sources of finance" from outside UN negotiating rooms.
The Bonn meeting will also feature discussions on the next round of national green plans, to be submitted by 2025, drawing on the UAE Consensus.
Germany has faced severe floods in recent days as a reminder of the threats posed by climate change. Warnings of "extreme danger" were issued in areas south of Bonn.
A firefighter died while trying to rescue people trapped by the flooding. Ministers were urged to put aside funds for major green investments on the scale of a military revamp.
"How many 'once-in-a-century' floods will it take until the government understands that this will be our new normal if it does not act?" said Sascha Muller-Kraenner of Environmental Action Germany.
Mr Stiell told delegates that, despite the progress made, the world is still heading for a "ruinously high" increase in global temperatures of 2.7°C above pre-industrial levels.
"It’s clear that the second half of humanity’s climate journey will be even harder, and climate action will need to move at a faster pace," he said. "We cannot afford rest stops or detours ... and we absolutely cannot afford to stumble in the next 10 days, or for global climate progress to stall this year and beyond."
