According to a risk study, ice sheets and ocean currents at danger of climatic tipping points might destabilize each other as the planet warms, resulting in a domino cycle with devastating repercussions for humankind.
Tipping points occur when global warming pushes temperatures past a critical point, with rapid and irreversible consequences. For example, some huge ice sheets in Antarctica are believed to have already reached their tipping points, implying significant sea-level rises in the next millennia.
The new study looked at the interconnections between West Antarctica's ice sheets, Greenland's ice sheets, the warm Atlantic Gulf Stream, and the Amazon rainforest. The researchers ran 3 million computer simulations and discovered domino effects in a third of them, even when the temperature increase was below 2 degrees Celsius, the Paris Agreement's top limit.
The researchers discovered that interactions between different climate systems can reduce the actual temperature thresholds at which each tipping point is reached. It was found that ice sheets can serve as a starting point for tipping cascades, with Atlantic currents functioning as a transmitter and eventually impacting the Amazon.
Prof Ricarda Winkelmann of the Potsdam Institute for Climate Impact Research (PIK) in Germany stated, "We present a risk analysis, not a prognosis, but our findings nonetheless arouse alarm." "[Our findings] may indicate that we have less time to cut greenhouse gas emissions while still avoiding tipping points."
She believes that the level of CO2 in the atmosphere necessary to drive temperatures above the thresholds will be achieved in the not-too-distant future. "We may be committing future generations to extremely terrible repercussions in the coming years or decades." For example, many meters of sea-level rise might result from glacier melting, devastating a slew of coastal communities.
"We're changing the chances, and they're not in our favor - the danger is obviously growing as we warm our planet," said Jonathan Donges, a member of the study team at PIK.
Ice Sheets Melting
Scientists announced in May that a large portion of the Greenland ice sheet was on the verge of melting. According to a 2019 study conducted by Prof Tim Lenton of the University of Exeter, the planet may have already passed through a series of climate tipping points, posing an "existential threat to civilization."
Researchers have warned that the climate crisis might push most of the Amazon to a tipping point, where the carbon-storing forest is replaced by grasslands. In addition, the Atlantic Meridional Overturning Circulation (AMOC), of which the Gulf Stream is a major component that keeps western Europe mild, is at its lowest in over a millennium.
The research, published in the journal Earth System Dynamics, used a new type of climate model because existing models are complex and require enormous computing power, making them expensive to run many times.
Instead, the researchers used an approach that focused explicitly on how the temperature thresholds for the tipping points changed as the systems interacted, allowing them to run the 3m simulations.
The melting of the Greenland ice sheet is an example of the intricate chain of interactions that the researchers studied. This adds freshwater to the ocean, slowing the AMOC, which is fueled in part by thick, salty water being drawn to the ocean floor.
A weaker AMOC implies that less heat is transferred from the tropics to the north pole, resulting in warmer Southern Ocean waters. This can destabilize Antarctic ice sheets, raising global sea levels and causing additional melting at the Greenland ice sheet's margins.
Climatic Tipping Points
"The analysis implies that there is still a serious danger of activating cascading climatic tipping points below 2°C of global warming - i.e., in the Paris accord goal range," said Lenton. "What the new study doesn't do is break down the timeframe during which tipping point shifts and cascades might occur; instead, it concentrates on the end results. Thus, the findings should be seen as "commitments" that we may soon make to possibly permanent alterations and cascades, leaving a bleak legacy for future generations."
According to Prof. Anders Levermann, who is also at PIK but was not involved in the current research, the likelihood of a cascade of tipping points leads to a runaway greenhouse effect. As a result, the globe becomes increasingly hotter even if humankind stops emitting carbon, which is highly improbable. Instead, he stated, "The Earth will be as heated as humans make it, which means we're the ones who have to stop it."
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