On the use of simple dynamical systems for climate predictions: A Bayesian prediction of the next glacial inception

TL;DR

This paper uses a Bayesian approach with a stochastic dynamical system to predict the timing of the next glacial inception, accounting for model limitations and uncertainties, and estimates it to occur in about 60,000 years.

Contribution

It introduces a Bayesian data assimilation method with particle filtering for low-order climate models to predict glacial cycles, explicitly handling model and parameter uncertainties.

Findings

Peak glacial conditions in approximately 60,000 years

Method accounts for model limitations and uncertainties

Demonstrates feasibility of Bayesian inference in climate prediction

Abstract

Over the last few decades, climate scientists have devoted much effort to the development of large numerical models of the atmosphere and the ocean. While there is no question that such models provide important and useful information on complicated aspects of atmosphere and ocean dynamics, skillful prediction also requires a phenomenological approach, particularly for very slow processes, such as glacial-interglacial cycles. Phenomenological models are often represented as low-order dynamical systems. These are tractable, and a rich source of insights about climate dynamics, but they also ignore large bodies of information on the climate system, and their parameters are generally not operationally defined. Consequently, if they are to be used to predict actual climate system behaviour, then we must take very careful account of the uncertainty introduced by their limitations. In this paper we consider the problem of the timing of the next glacial inception, about which there is on-going debate. Our model is the three-dimensional stochastic system of Saltzman and Maasch (1991), and our inference takes place within a Bayesian framework that allows both for the limitations of the model as a description of the propagation of the climate state vector, and for parametric uncertainty. Our inference takes the form of a data assimilation with unknown static parameters, which we perform with a variant on a Sequential Monte Carlo technique (`particle filter'). Provisional results indicate peak glacial conditions in 60,000 years.