Observationally constrained climate sensitivity implies high climate tipping risk

Global warming increases the risk of crossing climate tipping points, critical thresholds beyond which large-scale, potentially irreversible Earth system changes can be triggered. A major source of uncertainty in temperature projections is Equilibrium Climate Sensitivity (ECS). ECS measures long-term warming from a doubling of atmospheric CO2. We assess how ECS uncertainty affects tipping risk by feeding temperature projections from the climate emulator FaIR into PyCascades, which simulates interacting tipping elements. Higher ECS values strongly amplify the likelihood of crossing and triggering tipping points, showing a nonlinear, logistic relationship between ECS and tipping risk across a wide range of long-term CO2-stabilization levels. Under this relationship, recent observational constraints imply a long-term tipping risk of at least 82% under present-day CO2 concentration. In summary, overlooking the possibility of high climate sensitivity could lead to a disproportionate underestimation of tipping risks, necessitating a shift in how policymakers weigh the costs of continued carbon emissions.