Global warming must stay below 1.5°C

Twelve years to act or we will face catastrophic climate change. This is the core message of the report from the Intergovernmental Panel on Climate Change (IPCC) released on 8 October.1

The basis for this message is twofold. Firstly, we have already warmed the planet by 1°C above pre-industrial levels, with serious negative effects on people, ecosystems, and livelihoods worldwide. Secondly, unless we reduce greenhouse gas emissions decisively over the next 12 years, we will extend warming to beyond 1.5°C: the limit in the 2015 Paris agreement signed by 195 countries. For many ecosystems and populations, even this will fail to prevent disaster. However, the IPCC report describes why any failure to meet this target would have catastrophic effects.

The science of anthropogenic global warming and its effects have been previously explained in The BMJ.23 The IPCC’s new synthesis of more than 6000 recent scientific papers highlights once again the many dangers posed …