Can we still prevent critical climate tipping points?

Current climate policies carry a significant risk of triggering critical Earth system tipping points, even if global temperatures are later reduced to below 1.5°C after a temporary overshoot. A new study published in Nature Communications suggests that these risks can be mitigated if temperature increases are quickly reversed.

Human-induced climate change can destabilize large-scale Earth system components, known as tipping elements, such as ice sheets, ocean circulation patterns, and key global biospheres. 

Interconnected climate tipping points 

Researchers from the International Institute for Applied Systems Analysis (IIASA) and the Potsdam Institute for Climate Impact Research (PIK) examined the risks posed to four interconnected core climate tipping elements under current mitigation efforts and future emission scenarios.

The study focused on the potential destabilization of the Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC), and the Amazon Rainforest. 

These elements are crucial for maintaining the stability of the Earth’s climate system. Global warming can induce sudden changes in these systems, leading to irreversible outcomes.

The analysis emphasizes the critical importance of adhering to the climate targets set by the Paris Agreement and highlights the long-term consequences of our climate actions today. 

Climate tipping points in the coming centuries 

“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,” explained co-lead author Tessa Möller, a researcher with the IIASA Energy, Climate, and Environment Program and 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.” 

The study revealed that substantial tipping risks could materialize by 2300 under various future emission scenarios. If global temperatures do not return to below 1.5°C by 2100, despite achieving net-zero greenhouse gas emissions, there is up to a 24% chance that at least one of the key tipping elements will reach a critical threshold. This risk increases significantly with every tenth of a degree of warming above 1.5°C.

“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 2°C of global warming, tipping risks would escalate even more rapidly,” said co-lead author Annika Ernest Högner, a scientist at 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.” 

Rapid reversal of warming

The study stresses that only a rapid reversal of warming after any overshoot can effectively limit tipping risks. This necessitates achieving at least net-zero greenhouse gas emissions. 

“Our study underscores that this global mitigation objective, enshrined in Article 4 of the Paris Agreement, is vital for planetary stability,” said Carl Schleussner, leader of the IIASA Integrated Climate Impacts Research Group and one of the study’s authors

Interactions between climate tipping elements 

The researchers noted that current advanced models used to study Earth systems may not fully capture the complex behaviors, feedback loops, and interactions between tipping elements. 

To address these limitations, the team employed a simplified Earth system model using four connected mathematical equations to represent these tipping elements. This approach allowed them to include future stabilizing interactions, such as the cooling effect of a weakened AMOC on the Northern Hemisphere.

“This analysis of tipping point risks adds further support to the conclusion that we are underestimating risks, and need to now recognize that the legally binding objective in the Paris Agreement of holding global warming to well below 2°C, in reality, means limiting global warming to 1.5°C,” concluded PIK Director and study co-author Johan Rockström.

“Due to insufficient emission reductions, we run an ever-increasing risk of a period of overshooting this temperature limit, which we need to minimize at all costs to reduce dire impacts to people across the world.” 

The study’s findings highlight the urgent need for global action to limit global warming and prevent critical tipping points in the Earth’s climate system.

The potential irreversible changes underscore the importance of immediate and sustained efforts to reduce greenhouse gas emissions and adhere to international climate agreements.

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