Detecting Tipping Points in the Earth System from Climate Reconstructions

In the last 65 million years, the Earth’s climate has gradually cooled with a reduction in pCO2 and temperature along with the eventual glaciation of the poles. However, the gradual cooling trend is interspersed with events of abrupt and extreme climate shifts. Such aberrations could be explained by the passing of a ‘tipping point’, a critical threshold where self-reinforcing feedbacks propelling the system into an alternative stable state. The prospect of an impending critical transition could be detected by the loss of resilience of the system and resilience indicators have been developed to foretell an upcoming tipping point. The objective of this research is to test whether sudden shifts in paleoclimate reconstructions of the Cenozoic era could be due to self-reinforcing feedbacks. We will use data-driven indicators of resilience and causal feedbacks to find evidence for tipping point. The research will focus on the Palaeocene-Eocene Thermal Maximum (~56 Ma), Mid-Pleistocene transition(~1.25-0.7 Ma), Eocene-Oligocene transition (~34 Ma) and Mid-Miocene Climatic Optimum(~14-17 Ma), all of which have been speculated to have happened due to the passing of a tipping point. Some of these transitions have been studied before using resilience indicators, but here we will use recent high-resolution paleoclimate records to improve the predictions.