Huge tipping events have dominated the evolution of the climate system

An analysis of the hierarchy of tipping points reveals that over the course of the last 66 million years, two events played a major role in shaping the climate system. These events not only impacted the climate of the time but also set the stage for further climate tipping and the evolution of the climate system on a geological time scale, according to a study published in Scientific Reports.

The research, conducted by Denis-Didier Rousseau from Université Montpellier, France; Witold Bagniewski from Ecole Normale Supérieure, Paris, France; and Valerio Lucarini from the University of Reading, UK, is part of the European TiPES project focused on tipping points in the Earth System.

Drawn from the theory of evolution

This new insight into the history of climate change draws inspiration from the theory of punctuated equilibrium, which categorizes evolutionary changes into hierarchies.

Punctuated equilibrium, introduced in the 1970s by Eldredge and Gould as an alternative to classic evolution theory, suggests that certain evolutionary changes have a greater impact on the overall evolution of a species. It also explains why species tend to adapt through short bursts of evolution rather than gradual changes over time.

Rousseau and his colleagues theorized that a similar approach of ranking the importance of historical climate changes through tipping events could provide valuable insights. They applied advanced statistical methods to two sets of climate data that exhibited clear signs of critical transitions.

The analysis indeed supports the idea of hierarchies in the evolution of the climate system, uncovering two significant events that dominated the Earth’s climate system over the past 66 million years.

A sequence of climate tipping events

The first event occurred approximately 65.5 million years ago with the Chicxulub meteor impact in Mexico, which led to the extinction of large dinosaurs. This catastrophic event marked the beginning of a period of high CO2 levels and overall warm climate. For the next 30 million years, this regime influenced the possible climatic changes, keeping them within the boundaries of hot and warm climates.

The second crucial event took place around 34 million years ago with the tipping point associated with the glaciation of the Southern hemisphere. The isolation of the Antarctic continent at the South Pole due to plate tectonics resulted in the formation of a large ice sheet, leading to the glaciation of the Northern hemisphere as well. This marked the onset of a considerably colder climate on Earth, dictating the scope of future climate changes.

The analysis also suggests that our current global climate system still falls under this later climate regime and relies on the existence of the massive ice bodies formed during the Coolhouse/Icehouse era.

Significant implications

If the anthropogenic global warming causes the ice sheets to destabilize, deglaciation will become a landmark tipping point comparable to the two events that have shaped Earth’s history. This could lead to a new and unknown climate landscape.

“The ice sheets are crucial components of the present climate system, but they are highly sensitive. They are currently experiencing a negative mass balance, and there is evidence of melting due to climate warming, indicating a trend towards a potential tipping point that could accelerate the disappearance of Greenland and West Antarctica, with severe consequences for our societies,” says Rousseau.

“Crossing tipping points has been a recurring feature in climate evolution. Our study provides a better understanding of the mathematics behind such events. As a result, strategies for adaptation to and mitigation of climate change should now consider the possible destabilization of tipping elements,” adds Lucarini.

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