An Overview of Climatic Variability and its Causal Mechanisms

TLDR

Climatic variability spans timescales from hours to billions of years, as illustrated by a comprehensive variance spectrum. The study aims to interpret this spectrum by distinguishing internal stochastic mechanisms from external forcings. The authors define and clarify all identifiable internal and external mechanisms underlying climatic variability. Most spectral features can be tentatively interpreted, but key phenomena such as the quasi‑biennial oscillation and Holocene neoglacial cycle remain unexplained, indicating that while some deterministic climatic change exists, the substantial nonsystematic variability limits predictability and causal attribution in paleoclimate.

Abstract

A variance spectrum of climatic variability is presented that spans all time scales of variability from about one hour (10 −4 years) to the age of the Earth (4 × 10 9 years). An interpretive overview of the spectrum is offered in which a distinction is made between sources of variability that arise through stochastic mechanisms internal to the climatic system (atmosphere-ocean-cryosphere) and those that arise through forcing of the system from the outside. All identifiable mechanisms, both internal and external, are briefly defined and clarified as to their essential nature. It is concluded that most features of the spectrum of climatic variability can be given tentatively reasonable interpretations, whereas some features (in particular the quasi-biennial oscillation and the neoglacial cycle of the Holocene) remain fundamentally unexplained. The overall spectrum suggests the existence of a modest degree of deterministic forms of climatic change, but sufficient nonsystematic variability to place significant constraints both on the extent to which climate can be predicted, and on the extent to which significant events in the paleoclimatic record can ever manage to be assigned specific causes.