Past Abrupt Climate Changes and Tipping Points

Wed, 11 Jun 2025, 16:00 CEST

Conveners: Martin Claussen & Denis-Didier Rousseau

Although the Earth system has so far responded relatively smoothly to the drastic increase in anthropogenic greenhouse gases, there is rising concern that further rising temperatures may trigger nonlinear and abrupt responses in several components of the Earth system. The thresholds characterizing a transition from one stable system state to another are called 'Tipping Points' and are often associated with bifurcations in underlying dynamical systems, but they can also be triggered by noise or rate-induced effects. New methods are being developed to understand and to interpret abrupt changes found in paleoclimate proxy records. Evidence indicates that several components of the Earth system have indeed transitioned abruptly between different stable states in the past.

Guest speakers:

• Sebastian Bathiany (Technical University of Munich, Germany) – Paleo records, models, and dynamical systems theory: trinity of climate science, or triangle of sadness?
• Christo Bruizert (Oregon State University, USA) – An updated framework for global oceanic coupling of glacial abrupt climate change: an ocean heat valve.

Paleo records, models, and dynamical systems theory: trinity of climate science, or triangle of sadness?

Sebastian Bathiany

The hypothesis that human forcing could trigger nonlinear and even irreversible "tipping points" in the climate system is, to a large extent, based on paleo-climate evidence and dynamical systems theory. Climate models have often been found to behave relatively linearly, and direct observations of large-scale climate tipping events arguably don't exist. In my talk, I focus on the end of the Green Sahara and abrupt transitions in the Meridional Atlantic Overturning Circulation as examples of tipping points, and ask how knowledge on past climate changes, climate modelling, and mathematical theory may benefit each other.

An updated framework for global oceanic coupling of glacial abrupt climate change: an ocean heat valve

Christo Bruizert

Glacial Dansgaard–Oeschger (DO) climate oscillations provide prime examples of Earth System tipping points. They impact global climate and environmental conditions via an oceanic teleconnection pattern called the "bipolar seesaw", commonly conceptualized as an interhemispheric redistribution of heat via perturbations to the Atlantic Meridional Overturning Circulation. Here we evaluate recent paleoclimatic observations and model simulations of self-sustained DO oscillations to provide an updated framework for understanding the energetics of this global climate coupling that is focused on global ocean heat content.