According to a recent risk analysis study by an international team of researchers, temporarily exceeding the climate targets of 1.5-2 degrees Celsius could increase the tipping risk of several Earth system components by more than 70% compared to maintaining global warming within the United Nations Paris Agreement range.
Even if global temperatures were to stabilize within the Paris range over the long term, this risk of a tipping point would still exist.
The researchers conclude that preventing an overshoot would thereby reduce the risks.
Peak Temperature Increases Cause An Increase In At Least One Tipping Event
(Photo : ROBYN BECK/AFP via Getty Images)
The researchers used a variety of global warming overshoot scenarios with peak temperatures ranging from two to four degrees and applied these to a set of four interacting tipping elements: The Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation AMOC, and the Amazon rainforest, as per ScienceDaily.
The researchers also collaborated with co-authors from the Earth Commission, a group of top scientists brought together by Future Earth.
To account for the uncertainties in important parameters, including the uncertainty in critical temperature thresholds as well as interaction strengths and structure, the researchers used a risk analysis approach based on millions of model simulations.
Based on simulations using the fully coupled Earth System Model, performing this many simulations would be computationally prohibitively expensive.
The research team then examined the risk of exceeding critical thresholds and the potential for setting off cascading interactions between the four elements, depending on the size and duration of the overshoot as well as the amount of warming that would persist over the long term, for the various overshoot scenarios.
According to Nico Wunderling, "We found that the risk for the emergence of at least one tipping event increases with rising peak temperatures; at a peak temperature of three degrees Celsius, more than one-third of all simulations showed a tipping event even when overshoot durations were strongly limited, and at a peak temperature of four degrees Celsius, this risk extends to more than half of all simulations."
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Mechanisms for tipping under warming overshoots
The West Antarctic and Greenland ice sheets are particularly susceptible to tipping, making them some of the most vulnerable tipping elements, as per Eurekalert.
The temperature levels at which such changes are triggered could already be reached soon, according to Ricarda Winkelmann, Earth Commissioner and Co-Lead of the FutureLab on Earth Resilience in the Anthropocene.
While it would take a long time for the ice loss to fully manifest, she says. The other two tipping elements considered in the study, the AMOC and the Amazon rainforest, have higher critical temperature thresholds.
"Our action in the coming years can therefore decide the future trajectory of the ice sheets for centuries or even millennia to come," Winkelmann said.
By the end of this century, 2-3.6 degrees Celsius of global warming are anticipated as a result of current mitigation measures.
"This is insufficient. Although a temporary temperature overshoot would undoubtedly be preferable to reaching a peak temperature and staying there, some overshoot impacts could result in irreparable harm in a high-risk climate zone.
For this reason, low-temperature overshoots are crucial in this situation, according to Jonathan Donges.
Furthermore, every tenth of a degree matters, says Ricarda Winkelmann. To limit global warming as quickly as possible, we must take all necessary steps.
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