Dimensional analysis identifies contrasting dynamics of past climate states and critical transitions

TL;DR

This study uses dimensional analysis of isotope records to reveal how different climate states are governed by distinct timescales and degrees of freedom, improving understanding of past climate transitions and stability.

Contribution

It introduces a novel dimensional analysis approach to identify dominant timescales and mechanisms underlying various Cenozoic climate states and transitions.

Findings

Precession dominates Hothouse and Warmhouse states.

Obliquity and eccentricity influence Icehouse climate.

Abrupt shifts are identifiable within single climate states.

Abstract

While one can unequivocally identify past climate transitions, we lack comprehensive knowledge about their underlying mechanisms and timescales. Our study employs a dimensional analysis of benthic stable isotope records to uncover, across different timescales, how the climatic fluctuation of the Cenozoic are associated with changes in the number of effective degrees of freedom. Precession timescales dominate the Hothouse and Warmhouse states, while the Icehouse climate is primarily influenced by obliquity and eccentricity timescales. Notably, the Coolhouse state lacks dominant timescales. Our analysis proves effective in objectively identifying abrupt climate shifts and extremes. This is also demonstrated using high-resolution data from the last glacial cycle, revealing abrupt climate shifts within a single climate state. These findings significantly impact our understanding of the inherent stability of each climate state and the evaluation of (paleo-)climate models' ability to replicate key features of past/future climate states and transitions.