To tip or not to tip

Abstract. Tipping points have become a buzzword in Earth sciences, but ambiguous or overly narrow definitions of tipping are causing confusion around the concept. Agreeing on what tipping means, and whether a system tips or not, is important for robust science and communicating tipping risk. Based on a critical evaluation of existing tipping definitions, we propose a revised, general definition that characterizes a tipping event as a persistent nonlinear transition in forced systems. Our definition emphasizes both the phenomenology (observed time series) and cause (feedback mechanism) of a tipping event. Inspired by response theory, our proposition is compatible with more specific mathematical formulations while avoiding challenging notions such as bifurcations, equilibrium states, abruptness and irreversibility – making the definition testable also on transient dynamics in diverse complex systems under time-varying forcing. We showcase its practical use and limitations in a toy model and a case study of Earth system model data.