Scientists warn that we may be at a dangerous tipping point on global climate change.
So-called “tipping points” occur when global heating pushes temperatures beyond a critical threshold, leading to accelerated and irreversible impacts. Ice sheets and ocean currents at risk of climate tipping points can destabilize each other as the world heats up, leading to a domino effect with severe consequences for humanity, according to a risk analysis. According to a recent analysis, some large ice sheets in Antarctica are thought to have already passed their tipping points, meaning large sea-level rises in coming centuries.
The new research examined the interactions between ice sheets in West Antarctica, Greenland, the warm Atlantic Gulf Stream, and the Amazon rainforest. The scientists carried out thousands of computer simulations and found domino effects in a third of them, even when temperature rises were below 35F, the upper limit of the Paris agreement.
The study showed that the interactions between these climate systems could lower the critical temperature thresholds at which each tipping point is passed. It found that ice sheets are potential starting points for tipping cascades, with the Atlantic currents acting as a transmitter and eventually affecting the Amazon in a “domino-like” effect. This is cause for grave concern.
“We provide a risk analysis, not a prediction, but our findings still raise concern,” said Prof Ricarda Winkelmann at the Potsdam Institute for Climate Impact Research (PIK) in Germany. “[Our findings] might mean we have less time to reduce greenhouse gas emissions and still prevent tipping processes.”
The level of CO2 in the atmosphere required to push temperatures beyond the thresholds could be reached in the very near future, she said. “In the next years or decades, we might be committing future generations to really severe consequences.” These could include many hundreds of feet of sea-level rise from ice melting, affecting scores of coastal cities.
“We’re shifting the odds, and not in our favor – the risk clearly is increasing the more we heat our planet,” said Jonathan Donges, also at PIK and part of the research team.
As recently as May, scientists reported that a significant part of the Greenland ice sheet was on the brink of a tipping point. A 2019 analysis led by Prof Tim Lenton at the University of Exeter suggested the world may already have crossed a series of climate tipping points, resulting in what the researchers called “an existential threat to civilization.”
The climate crisis may also mean much of the Amazon is close to a tipping point, at which carbon-storing forest is replaced by savannah, researchers have warned. As we reported on these pages, the ocean currents of the Atlantic Meridional Overturning Circulation (AMOC), of which the Gulf Stream is an important part and keeps western Europe mild, are at their weakest in more than a millennium.
Despite the risk analysis indicating cause for alarm, the scientists agree that proper intervention can avert disaster. They believe that the chance of a cascade of tipping points leading to a runaway greenhouse effect is unlikely to occur if humanity gets carbon emissions under control.
Prof. Anders Levermann — also at PIK but not involved in the aforementioned new risk analysis – said, “The Earth will get as warm as we make it, which means we’re the ones [that must] stop it.”