Stochastic Resonance Elucidates the Emergence and Periodicity Transition of Glacial Cycles

Glacial cycles emerged with a 41-kyr period after the Pliocene and intensified with a 100-kyr period in the mid-Pleistocene, which were attributed to Earth's orbital variations. However, no significant changes in the orbital forcing were found at the two transitions, and the forcing was too small to drive these cycles. Here, a stochastic resonance model is proposed to resolve these two issues. Earth's radiative imbalance varies with temperature but is modulated by non-stationary greenhouse gas concentrations leading to a persisting warm state (the inter-glacials) and a colder state (the glacials) only in the Pleistocene. A noise that encodes volcanic eruptions and short-term climate variations acts to trigger glacial-interglacial jumps modulated by periodic orbital variations. The mid-Pleistocene transition to the 100 kyr world is shown to be favored by a weakened noise amplitude. This formulation offers a unified view of Pliocene-Pleistocene evolution that can be extended to hothouse and snowball climates.