To accept that the world’s average temperature might rise by more than 1.5 deg C, declared the foreign minister of the Marshall Islands in 2015, would be to sign the “death warrant” of small, low-lying countries such as his. To widespread surprise, the grandees who met in Paris that year, at a climate conference like the one that has started in Egypt this week, accepted his argument. They enshrined the goal of limiting global warming to about 1.5 deg C in the Paris Agreement, which sought to coordinate national efforts to curb emissions of greenhouse gases.

No one remembered to tell the firing squad, however. The same countries that piously signed the Paris Agreement have not cut their emissions enough to meet its targets; in fact, global emissions are still growing. The world is already about 1.2 deg C hotter than it was in pre-industrial times. Given the lasting impact of greenhouse gases already emitted, and the impossibility of stopping emissions overnight, there is no way the earth can now avoid a temperature rise of more than 1.5 deg C. There is still hope that the overshoot may not be too big, and may be only temporary, but even these consoling possibilities are becoming ever less likely.