A Punctuated Equilibrium Analysis of the Climate Evolution of Cenozoic exhibits a Hierarchy of Abrupt Transitions

The Earth’s climate has experienced numerous critical transitions during its history, which have often been accompanied by massive and rapid changes in the biosphere. Such transitions are evidenced in various proxy records covering different timescales. The goal is then to identify, date, characterize, and rank past critical transitions in terms of importance, thus possibly yielding a more thorough perspective on climatic history. To illustrate such an approach, which is inspired by the punctuated equilibrium perspective on the theory of evolution, we have analyzed 2 key high-resolution datasets: the CENOGRID marine compilation (past 66 Myr), and North Atlantic U1308 record (past 3.3 Myr). By combining recurrence analysis of the individual time series with a multivariate representation of the system based on the theory of the quasi-potential, we identify the key abrupt transitions associated with major regime changes that separate various clusters of climate variability. This allows interpreting the time-evolution of the system as a trajectory taking place in a dynamical landscape, whose multiscale features describe a hierarchy of metastable states and associated tipping points.

The analysis reveals that two major events out of the ten dominated the evolution of the Earth's climate system over the last 66 million years. The first event was the Chicxulub meteor impact in Mexico, which killed off the large dinosaurs approximately 65,5 million years ago. This catastrophe marked the beginning of a very warm period with high levels of CO2. For the following 30 million years this regime dictated which climatic changes were possible and kept it within the regime of hot and warm climates.

The second crucial event was the tipping point associated with the glaciation of the Southern hemisphere 34 million years ago when the Antarctic continent was isolated at the South Pole due to plate tectonics. The forming of the large ice sheet led to the glaciation of the North as well and marked the beginning of a considerably colder type of climate on Earth, again dictating the scope of future climate changes.

The analysis additionally suggests that our current global climate system still belongs to the latter climate regime and still depends on the existence of the gigantic ice bodies built within the Coolhouse/Icehouse era. In the event that the ice sheets should not withstand anthropogenic global warming, the deglaciation will therefore represent a landmark tipping point similar to the two that have dominated Earth's history leading to a new unknown climate landscape.

Rousseau, DD., Bagniewski, W. & Lucarini, V. A punctuated equilibrium analysis of the climate evolution of cenozoic exhibits a hierarchy of abrupt transitions. Sci Rep 13, 11290 (2023). doi: 10.1038/s41598-023-38454-6