According to a risk analysis by the Potsdam Institute for Climate Impact Research (PIK) in Germany, the interactions between these climate systems can 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.
Climate tipping points can destabilise each other as the world heats up, leading to a domino effect with severe consequences for humanity. Tipping points occur when global heating pushes temperatures beyond a critical threshold, leading to accelerated and irreversible impacts. Some large ice sheets in Antarctica are thought to already have passed their tipping points, meaning large sea-level rises in coming centuries.
“We provide a risk analysis, not a prediction, but our findings still raise concern,” said Prof Ricarda Winkelmann. “Our findings might mean we have less time to reduce greenhouse gas emissions and still prevent tipping processes.” The level of CO 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 metres of sea-level rise from ice melting, affecting scores of coastal cities.
“We’re shifting the odds, and not in our favour – the risk clearly is increasing the more we heat our planet,” said Jonathan Donges
An example of the complex chain of interactions the researchers tracked is the melting of the Greenland ice sheet. This releases fresh water into the ocean and slows down the AMOC, which is driven partly by dense, salty water being pulled down towards the ocean floor. A weaker AMOC means less heat is transported from the tropics towards the north pole, which in turn leads to warmer waters in the Southern Ocean. This can then destabilise ice sheets in Antarctica, which pushes up global sea level and causes more melting at the edges of the Greenland ice sheet.
Prof Tim Lenton at the University of Exeter explained, “The study suggests that below 2C of global warming – ie in the Paris agreement target range – there could still be a significant risk of triggering cascading climate tipping points.” Lenton went on to say, “What the new study doesn’t do is unpack the timescale over which tipping points changes and cascades could unfold – instead it focuses on the eventual consequences. The results should be viewed as ‘commitments’ that we may be making soon to potentially irreversible changes and cascades, leaving as a grim legacy to future generations.”
More optimistically, Prof Anders Levermann stated that the chance of a cascade of tipping points leading to a runaway greenhouse effect, where the planet gets ever hotter even if humanity stops carbon emissions, is extremely unlikely.
“The Earth will get as warm as we make it, which means we’re the ones that must stop it,” he said.