'The world we know is over': Leaders warn Cop31 that overshoot demands an overwhelming climate response

Hilda Heine, president of the Marshall Islands, told the heads of state gathered at the Cop31 climate summit in Turkey on Wednesday that she had seen the water around her home island in July filled with bright, lush coral. Within months, she said, it had bleached white. It was the image she used to anchor a warning: if governments fail to answer the threat of overshooting the 1.5C Paris temperature target with an overwhelming response, "the world we know is over."

Heine was one of a handful of Pacific Island leaders to give an impassioned speech on day three of the conference, the opening of the leaders' summit. Overshoot, she said, would mean waves eating away shorelines and floods destroying towns, schools and hospitals. She also took aim at fossil fuel expansion, saying every new oil well and every piece of coal extracted threatens her country's future. Without naming any producer, she said the discovery of new fossil fuel resources is "not something to celebrate but something to fear."

Mia Mottley, prime minister of Barbados, put numbers to the gap. The UN, she said, tells us that even if every pledge is delivered the world is heading for 2.6 degrees of warming, and on current policies it will reach 2.8. She described overshoot as "a debt of heat, borrowed against our children's future," and said it must be repaid. She also criticised governments that had "not tried hard enough" to cut emissions since the Paris agreement.

UN Secretary General António Guterres, who steps down next month and was delivering one of his last major climate speeches in the role, blamed a deceitful fossil fuel industry and countries that keep expanding production while claiming to be committed to 1.5C. "It's make or bake time," he said, calling for an "extraordinary acceleration." He argued that fossil fuels will not disappear on their own, because "the dinosaurs did not have a lobby – fossil fuels do." He said oil and gas companies had distorted science and delayed action, and urged governments to tax the windfall profits the industry has made from the Iran war and use the money to help vulnerable countries recover. "Polluters must pay," he said, to applause.

The summit has an unusual structure: Turkey is co-hosting with Australia, and both leaders praised the arrangement. Recep Tayyip Erdoğan said he wants Cop31 remembered as a turning point and urged countries to act rather than simply promise. Yet on Monday, outside the conference hall, he celebrated the discovery of two new oilfields with an estimated in-situ potential of 135m barrels. Anthony Albanese called the conference a "historic moment" for Australia, one of the world's biggest exporters of coal and liquefied gas, and spoke of a "solemn responsibility" to act. He was criticised for not mentioning fossil fuels in his speech.

The gathering was relatively thin. The UN said 91 national leaders attended, but Donald Trump and Xi Jinping were absent. Emmanuel Macron and Friedrich Merz also stayed away; they are instead heading to Ireland for a conference on AI. Almost every country at the summit is lagging on cutting emissions, and finance for the nations most exposed to extreme heat, floods and fires remains insufficient.

The scientific backdrop is bleak. The world is passing the 1.5C limit and entering one of the strongest El Niño events in history. The UN Environment Programme has found overshoot is now inevitable, and warned that its effects on icy regions would be so calamitous that it should be kept as brief and low as possible. Bill Hare, a climate scientist and chief executive of Climate Analytics, described a "feeling of panic" among scientists, including those studying rainforests and the cryosphere. "The mood is gradually darkening," he said, adding that people talk of things having gone backwards.

Other leaders echoed the urgency. North Macedonia's president, Gordana Siljanovska-Davkova, said this is the first generation to fully understand the consequences of its choices, and perhaps the last with time to change course. Slovenia's president, Nataša Pirc Musar, asked what is left to unite countries if they cannot agree that human dignity and respect for nature belong at the heart of decisions. Despite the rhetoric, there is little sign the talks will deliver new progress on phasing out fossil fuels.