Permafrost and ice sheets: potential abrupt and/or irreversible changes

This short article presents a summary of a public lecture held at the Académie des Sciences in March, 2024 on continental tipping elements in the climate system. It first discusses some critical aspects of the tipping elements/tipping points concept as currently used in climate science. It is argued that using more clearly defined concepts such as abruptness and irreversibility instead of the “tipping element” framing, as done in the IPCC AR6 WGI report, can avoid confusion. The permafrost carbon reservoir and large continental ice sheets are then presented as prime examples of climate system elements possibly subject to abrupt and irreversible changes.