“We’ve failed to act on the options that were available 15 or 20 years ago to reduce emissions rapidly,” said report co-author Joeri Rogelj, a climate scientist at the International Institute for Applied Systems Analysis in Austria and a professor at Imperial College London. “The reality is that we have failed in that endeavor, and it needs to be acknowledged.”

The new report does just that, and it is alarming because the climate impacts projected for warming above 1.5 degrees Celsius are “unacceptable or unbearable for at least the poorest and the most vulnerable communities around the world,” he said. This summer, with heatwaves that killed thousands in Europe and burned parts of towns in North America, showed that developed countries in the Global North are not immune, he added.