Countries agreed a deal at the COP29 climate conference on Saturday on rules for a global market to buy and sell carbon credits that proponents say will mobilise billions of dollars into new projects to help fight global warming.

Even as a big climate finance goal remains elusive, COP negotiators in Azerbaijan are advancing rules for carbon credits trading between countries.

New rules allowing wealthy polluting countries to buy carbon-cutting "offsets" from developing nations were agreed at UN climate talks Saturday, in a move already raising fears they will be used to greenwash climate targets.

Countries walk out as a bitter fallout erupts between poorer and richer countries over money to help tackle climate change.

COPs have been getting progressively longer; the excellent team at Carbon Brief extrapolated the trend line, which suggests COP29 will end in the small hours of Sunday morning. Even that may be optimistic.