An international team of scientists has published a study in the Proceedings of the National Academy of Sciences (PNAS) this August showing that even if humanity sticks to the Paris Agreement, there is a risk the Earth could enter what scientists call “Hothouse Earth” conditions. The paper examines how vital carbon sinks, such as forests and oceans, might perform under two degrees of warming and if there is a danger they could turn from sinks to sources, thereby accelerating global warming. The paper seeks to establish whether such a threshold might exist and if so, where it might be. The authors warn the earth’s climate could stabilise at a global average of 4-5°C higher than pre-industrial temperatures, higher than any time in the past 1.2 million years, with sea level 10-60 m higher than today. They conclude it is now urgent to greatly accelerate the transition towards an emission-free world economy.