PMeanwhile, Johan Rockström, the driving force behind the whole Planetary Boundaries framework, is now spelling it out as starkly as it needs to be:

“A 2.5°C global mean surface temperature rise is a disaster. It’s something that humanity has absolutely no evidence that we can cope with. There would be a 10-metre sea level rise. There would be a collapse of all the big biomes of planet Earth – the rainforest, many of the temperate forests, abrupt thawing of permafrost, and the complete collapse of marine biology. Over 1/3rd of the planet around the equatorial regions will be unhabitable because you will pass the threshold of health, which is around 30°C. It’s only some parts of the Sahara Desert today that has that kind of average temperature.”