How much more global warming can we take? Rising temperatures are bringing us close to multiple climate tipping points

Written by Rebecca Sharland, Science Communication and Public Engagement Masters student at the University of Edinburgh and Dr Michael Byrne, leader of the Climate Dynamics Lab at the University of St Andrews.

COP27 is taking place this week in Sharm el-Sheikh, Egypt. High on the agenda will be issues surrounding the Paris Agreement and discussions on how nations can work together to keep the global temperature rise below 1.5°C – a significant change given that the Earth has already warmed by 1.1°C and could reach 1.5°C as soon as the 2030s.

What did the study show and what are climate tipping points?

Climate tipping points occur when changes in large parts of the climate system become self-perpetuating beyond a warming threshold and result in irreversible alterations to the Earth system, for example collapsing ice sheets causing sea level rise.

A recent study in Science has re-evaluated climate tipping points (see some examples in the table below) and the global warming thresholds at which they are likely to be triggered. Some of tipping points assessed were global, affecting the overall operation of the Earth system (e.g., major ice sheet collapses or the Amazon rainforest turning to desert); while others were more regional affecting human welfare or unique features of the Earth system (e.g., coral bleaching in the Great Barrier Reef).

As we approach the minimum temperatures at which these tipping points may occur, the question arises about the accuracy of the estimated thresholds (based on climate modelling) and whether some of these have already been surpassed.

The paper states that we must stay on track with the Paris agreement, and push to keep global warming below the 1.5°C target as the threat of activating tipping points increases for every fraction of a degree of warming. They warn that the Earth may already have passed beyond a safe state with our current 1.1 degree celsius of warming above pre-industrial levels.

What did the media report?

The Guardian published an article titled “World on brink of five ‘disastrous’ climate tipping points, study finds” based on the above study.

Initially, the article takes a very alarmist approach. The word ‘disastrous’ is not used in the research study itself and the temperatures at which the final six tipping points could be triggered are exaggerated (the article states that they will occur anywhere above 2°C, however many of the thresholds are around 4°C with some are as high as 7.5°C).

However, the article contains interviews with members of the research team who highlight both the dangers of triggering these tipping points and their hope for prevention. Several researchers also mention uncertainty around the global warming thresholds at which these tipping points will be triggered and the urgent need for further investigation.

Disappointingly, the key message from the original research study, that we must strive to meet the terms of the Paris Agreement, is somewhat lost in this news article. It is only mentioned briefly as a quote from an interview and is not highlighted by the journalist.

What next?

It is important to raise awareness of the dangers posed by global warming; The Guardian article does this well, emphasising how disastrous passing these global tipping points would be. Nevertheless, it is also necessary to highlight the preventable nature of these changes, the amount of further research required and the substantial uncertainty involved in trying to predict if and when these tipping points will be crossed. We are at a very critical point with global warming where we must aim to minimise increases in the Earth’s temperature; if and how we are going to do this will be key questions during COP27 discussions this month.