On 9 November, delegates from more than 190 countries will begin arriving in Antalya, a Turkish resort city on the Mediterranean, for two weeks of climate negotiations. The arrangement is unusual even by the standards of UN diplomacy. Turkey will host the summit, but Australia will preside over the formal negotiations, a compromise reached after both countries claimed the right to lead. The division of labour is deliberate.

Australia will steer the legally significant work: the "just transition" for workers in fossil fuel industries, climate finance, and efforts to keep warming as close as possible to the 1.5C goal set in the 2015 Paris agreement. Turkey will run the "action agenda", a set of voluntary initiatives on methane, food security, waste, the circular economy and, arguably most important, the electrification of the global economy. Nearly all of the 196 original Paris signatories are expected to attend.

The conspicuous exception is the United States, whose president, Donald Trump, has withdrawn from the agreement. The central difficulty is that the 1.5C threshold has already been crossed. The UN's argument is that fast cuts in emissions could limit this "overshoot" and allow temperatures to fall again by the end of the century, but only if countries abandon fossil fuels and adopt low-carbon technologies far more quickly.

Two roadmaps from Brazil, one on moving away from fossil fuels and one on halting deforestation, will propose ways to do it. Meanwhile, poorer nations are demanding practical help.