Talk by Niklas Boers and TiPES colleagues

Title: Abrupt transitions in paleoclimate: Uncertainties, mechanisms, and early-warning signs

Abstract: Paleoclimate evidence suggestes that several subsystems of the Earth system may abruptly change their state as a response to gradual changes in (anthropogenic) forcing. Key examples include the Atlantic Meridional Overturning Circulation (AMOC) and the polar ice sheets. We will present recent results on dynamical-system approaches to model the key dynamics of these subsystems, including potential early-warning systems for destabilization. We will start with paleoclimate evidence of abrupt transitions in the long-term past with a focus on the Dansgaard-Oeschger events, for which we will first present a Bayesian apoproach to propagate dating uncertainties to the proxy axis, leading to a representation of the time series as a sequence of probability densitiy functions. We then use the sequence of probability density functions to identify abrupt transitions in the past climate within an uncertainty-aware framework. Using recurrence analysis, we estimate the likelihood of a non-random transition within a chosen time window by identifying block-like structures in probability of recurrence plots. Therafter, we will discuss more recent empirical evidence for increasing melt rates of the Greenland ice sheet and potential dynamical-system indicators for an ongoing destabilization.