A risk assessment framework for interacting tipping elements

Abstract

Tipping elements, such as the Greenland Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC) or the Amazon rainforest, interact with one another and with other non-linear systems such as the El Niño-Southern Oscillation (ENSO). In doing so, the risk of any one element being degraded can be drastically affected, typically increasing due to the interactions. Therefore, in this work we propose a fully probabilistic network model for risk assessment of interacting tipping elements that coherently incorporates literature-based expert assessments of inter-element interactions. For fixed levels of global warming, we provide analytic results for the risk of being degraded for 8 interacting tipping elements and ENSO at equilibrium, including the stability of and convergence times to this equilibrium solution. Moreover we simulate their tipping risks until 2350 using emission pathways from the Shared Socio-economic Pathways (SSP 1-1.9, 1-2.6, 2-4.5, 3-7.0, and 5-8.5). Compared to the interaction-free baseline, we find that interactions tend to destabilise the climate system. For instance the coral reefs are likely to have collapsed by 2100 even under the most optimistic scenario (SSP1-1.9). The effects of interactions, however, are most noticeable after 2100, especially for the SSP scenarios with the strongest greenhouse gas emissions (SSP3-7.0 and SSP5-8.5). In summary, our risk assessment framework for tipping elements and ENSO indicates that rapid mitigation is essential to keep temperatures as close as possible to 1.5 °C in the short term and below 1 °C in the longer run.