As global temperature increase shoots past 1.5 degrees Celsius, vulnerable countries confront a brutal new reality. The most ambitious part of the 2015 Paris climate agreement, to limit global warming to 1.5 degrees Celsius, only came about because of a campaign by some of the world's poorest and most defenseless nations. Caribbean participants tacked up posters saying '1.5 to stay alive,' and the prime minister of Tuvalu said any temperature rise beyond that mark would 'spell the total demise' of his and other low-lying island nations.

Cutbacks in aid from wealthy nations, including the United States, have reduced the humanitarian safety net. The United States, the world's largest historical emitter, has also withdrawn from the Paris Agreement, as well as from funds meant to help developing countries deal with climate change. Poorer nations say these changes threaten to make the 1.5 Celsius breach even rockier, leaving them fewer resources to deal with disasters while widening global inequities.

The fault line between wealthy, industrialized nations and poor, developing nations has long been a defining feature of international climate talks. The U.N. report on the 'overshoot' of 1.5 Celsius, issued on Sept. 2, figures to create extra tensions when countries meet for the annual climate summit in Antalya, Turkey. A negotiating bloc representing 44 nations known as the Least Developed Countries this month raised the idea of a tribunal to assess potential climate 'reparations.'