Orbital insolation variations, intrinsic climate variability, and Quaternary glaciations

The relative role of external forcing and of intrinsic variability is a key question of climate variability in general and of our planet's paleoclimatic past in particular. Over the last 100 years since Milankovic's contributions, the importance of orbital forcing has been established for the period covering the last 2.6 Myr and the Quaternary glaciation cycles that took place during that time. A convincing case has also been made for the role of several internal mechanisms that are active on timescales both shorter and longer than the orbital ones. Such mechanisms clearly have a causal role in Dansgaard-Oeschger and Heinrich events, as well as in the mid-Pleistocene transition. We introduce herein a unified framework for the understanding of the orbital forcing's effects on the climate system's internal variability on timescales from thousands to millions of years. This framework relies on the fairly recent theory of non-autonomous and random dynamical systems, and it has so far been successfully applied in the climate sciences for problems like the El Nino-Southern Oscillation, the oceans' wind-driven circulation, and other problems on interannual to interdecadal timescales. Finally, we provide further examples of climate applications and present preliminary results of interest for the Quaternary glaciation cycles in general and the mid-Pleistocene transition in particular.

Automated summary

The relative importance of external forcing and intrinsic variability in climate change is a key question in understanding both general climate variability and the paleoclimatic history of our planet. Research over the past century has established the significance of orbital forcing in the last 2.6 million years and the Quaternary glaciation cycles. Internal mechanisms have also been found to play a causal role in events such as Dansgaard-Oeschger and Heinrich events as well as the mid-Pleistocene transition. This study introduces a unified framework that utilizes the theory of non-autonomous and random dynamical systems to understand the effects of orbital forcing on the climate system's internal variability over timescales ranging from thousands to millions of years.