After a week of negotiations in Addis Ababa, the world's most important climate science panel closed its meeting on Friday with a gap where a date should have been. The Intergovernmental Panel on Climate Change (IPCC) made progress on several fronts, but its member governments could not agree when to publish AR7, the seventh comprehensive assessment of what is known about the climate. The failure comes less than a month before governments gather for the Cop31 summit. The expected timetable was 2028, seven years after the previous report appeared in 2021.

A loose group of countries led by Saudi Arabia, Russia and India, and including China and Kenya, has resisted that schedule. Their argument is that climate science is dominated by wealthy countries, and that this has skewed its conclusions. They would prefer 2029 or later. Scientists see a practical problem in that proposal.

In 2028 the Paris agreement requires its second "global stocktake", in which national emissions pledges are checked against the goal of holding warming to 1.5C above preindustrial levels. Those talks are expected at Cop33 in late 2028, and a report published after them could not inform them. Critics also note that Saudi Arabia has a long record of trying to weaken earlier IPCC reports, and that employees of its oil company and scientists with oil links sit on IPCC committees.

Would a delay actually bring in more research from developing countries?