The weather in Belém, wrote the Guardian’s environment editor, offers a convenient metaphor for the UN climate talks being held in the Brazilian city. Sunny mornings begin in blazing optimism before the Amazon’s clouds gather and the deluge begins. Cop30 has followed the same pattern. It opened with sunshine – an agenda agreed on day one. The storms were deferred for later “consultations” on climate finance, carbon border tariffs and the question of how to close the yawning gap between national climate pledges and the Paris agreement’s safe pathway. These await Cop30’s second week.

They are likely to be more than mere squalls. The International Energy Agency confirmed last week that the fossil-fuel era is ending. Its annual report said the world will hit peak coal, oil and gas this decade and see declines thereafter. The economist Fadhel Kaboub, who advises developing nations on climate, argues this is not “because of political will, but because the economics of renewables is winning”. Africa, he says, can generate about 1,000 times the electricity it will need in 2040 – which could be exported. Globally, however, hydrocarbon use is easing far too slowly. The fight over money and a just transition matters at Cop30.

The dispute is how to keep heating to just 1.5C above preindustrial levels. The global south pushes the agreement’s article 9.1, which says that rich nations “shall provide” the funds developing countries need to go green. The rich states retreat to the text’s article 6, which highlights carbon markets. Developing countries want rich-world historic emitters to provide the cash, mainly for adaptation and ideally as grants. Wealthy ones counter that the focus should be on market opportunities to cut emissions, with newly industrialised states sharing the load and public funds blended with loans as well as private capital. This is not a technical spat. It is a fight over who pays for a managed, fair fossil-fuel phase-out.

The sums at stake are eye-popping. Last year, developing countries argued for $1.3tn a year in climate finance – the minimum they say is needed to fund resilience and basic infrastructure. What they got was a promised $300bn by 2035, much of it loans or “mobilised” private finance. The latest data shows that a third of the cash materialised. Worse, ActionAid’s analysis of around $19bn in climate aid over a decade found that under 3% backed a “just transition” for workers and communities.

Clouds will gather over Belém. The test will be whether this year’s UN summit can improve on the last. The absence of Donald Trump – or anyone from his administration – may actually help. At the negotiations, the developing nations’ G77 group plus China have pushed a “just transition mechanism” to formalise climate cooperation, transfer green tech and channel support into debt-free finance. They are backed by Brazil, South Africa and India. Developed nations argue that this risks a delay in reaching climate goals.

The Earth is headed for 2.6C of heating this century – producing a dangerously unstable world, but an improvement on the 3.6C trajectory of a decade ago. Richer nations spend billions on holders of their government bonds, but cry poverty when it comes to coughing up for the climate emergency they largely created. Cop30 will either see the global north accept that it can – and must – pay its fair share, or watch wealthy nations keep wringing their hands as the planet burns.