Interacting tipping elements increase risk of climate domino effects

The Greenland Ice Sheet, West Antarctic Ice Sheet, Atlantic Meridional Overturning Circulation (AMOC), El-Nino Southern Oscillation (ENSO) and the Amazon rainforest have been identified as potential tipping elements in the Earth system, exhibiting threshold behavior. While their individual tipping thresholds are fairly well understood, it is of yet unclear how their interactions might impact the overall stability of the Earth’s climate system. Here, we explicitly study the effects of known physical interactions using a paradigmatic network approach which is not yet possible with more complex global circulation models or process-based models in a comprehensive way.

We analyze the risk of domino effects being triggered by each of the individual tipping elements under global warming in equilibrium experiments, propagating uncertainties in critical temperature thresholds and interaction strengths via a Monte-Carlo approach.

Overall, we find that the interactions tend to destabilize the network, with cascading failures occurring in 41% of cases in warming scenarios up to 2°C. More specifically, we uncover that:

(i) With increasing coupling strength, the temperature thresholds for inducing critical transitions are lowered significantly for West Antarctica, AMOC, ENSO and the Amazon rainforest. The dampening feedback loop between the Greenland Ice Sheet and the AMOC due to increased freshwater flux on the one hand and relative cooling around Greenland on the other, leads to an enhanced ambivalency whether the Greenland Ice Sheet tips or not.

(ii) Furthermore, our analysis reveals the role of each of the five tipping elements showing that the polar ice sheets on Greenland and West Antarctica are oftentimes the initiators of tipping cascades (in up to 40% of ensemble members for Greenland), while the AMOC acts as a mediator, transmitting cascades.

This implies that the ice sheets, which are already at risk of transgressing their temperature thresholds within the Paris range of 1.5 to 2°C, are of particular importance for the stability of the climate system as a whole.