If global warming exceeds the 1.5°C target set by the Paris Agreement, it could lead to unstable Earth systems. However, a new study suggests that if this target is surpassed, swiftly reversing the warming could minimize the resulting impacts.
This study, led by the International Institute for Applied Systems Analysis (IIASA) and the Potsdam Institute for Climate Impact Research (PIK), along with researchers from Imperial College London, demonstrates the potential to minimize the impacts of exceeding the 1.5°C target.
“Our results show why reducing emissions this decade is crucial for the state of the planet. Failing to reach the Paris Agreement target risks reshaping the Earth’s systems for centuries to come,” said Co-author Dr Robin Lamboll, from the Centre for Environmental Policy and the Grantham Institute at Imperial.
Human-induced climate change has the potential to destabilize crucial components of the Earth’s system, such as ice sheets, ocean circulation patterns, and large biospheres. These components, known as ‘tipping elements,’ undergo irreversible changes once their state is altered. For example, ice sheets can melt much faster than they grow.
In a recent study, researchers assessed existing levels of climate action and various scenarios for future greenhouse gas emissions to evaluate the risk of destabilizing four critical tipping elements: the Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation (the primary ocean current system in the Atlantic Ocean), and the Amazon Rainforest.
The authors’ findings reveal a significant risk of tipping over at least one crucial element by the year 2300 under several future emission scenarios. If we fail to achieve a return to below 1.5°C by 2100, even after reaching net-zero greenhouse gas emissions, there is a risk of up to 24% of tipping by 2300. This means that in approximately a quarter of model runs, at least one of the critical tipping elements has already been tipped.
“We see an increase in tipping risk with every tenth of a degree of overshoot above 1.5°C. If we were to also surpass two °C of global warming, tipping risks would escalate even more rapidly,” said co-author Annika Ernest Högner from PIK. “This is very concerning as scenarios that follow currently implemented climate policies are estimated to result in about 2.6°C global warming by the end of this century.”
“Our results show that to effectively limit tipping risks over the coming centuries and beyond, we must achieve and maintain net-zero greenhouse gas emissions,” said co-lead author Tessa Möller, a researcher in the IIASA Energy, Climate, and Environment Program at PIK. “Following current policies this century would commit us to a high tipping risk of 45% by 2300, even if temperatures are brought back to below 1.5°C after a period of overshoot.”
According to researchers, the current advanced Earth system models are unable to capture the complex behaviors and interactions of tipping elements fully.
To address this, a team utilized a simplified Earth system model with four interconnected mathematical equations to represent these tipping elements. This approach also considers future stabilizing interactions, such as the cooling effect of the weakening Atlantic Meridional Overturning Circulation on the Northern Hemisphere.
Co-author Dr Carl Schleussner, IIASA Integrated Climate Impacts Research Group Leader, said: “Only a swift warming reversal after overshoot can effectively limit tipping risks. This requires achieving at least net-zero greenhouse gases. Our study underscores that this global mitigation objective, enshrined in Article 4 of the Paris Agreement, is vital for planetary stability.”
Journal reference:
- Tessa Möller, Annika Ernest Högner, Carl-Friedrich Schleussner, Samuel Bien, Niklas H. Kitzmann, Robin D. Lamboll, Joeri Rogelj, Jonathan F. Donges, Johan Rockström & Nico Wunderling. Achieving net zero greenhouse gas emissions critical to limit climate tipping risks. Nature Communications, 2024; DOI: 10.1038/s41467-024-49863-0
