Abrupt and Sudden Climatic Transitions and Fluctuations: a Review

This review paper summarizes recent research work on abrupt climatic changes and oscillations. The climatic system is viewed as a dissipative, highly non-linear system, under non-equilibrium conditions, and, as such, should be expected to have some unusual properties. These unusual properties include bifurcation points with marked instability just before the point, magnification of semi-periodic oscillations around bifurcation points, and variations in the strength of teleconnections with distance from equilibrium. These properties are discussed and illustrated for the climatic system using both the historical, Holocene and glacial climatic records. It is found that there are abrupt climatic changes and oscillations on all time-scales. The amplitudes and frequencies of climate variability and teleconnections are found to vary between different time periods. A number of persistent oscillations exist, particularly one about 1500 years, but their amplitudes vary considerably between time periods. The Holocene appears to be no more climatically benign than the similar period in the Eemian. The importance of the North Atlantic thermohaline circulation for generating abrupt climatic changes in Europe, particularly in association with sudden pulses of fresh water, is illustrated. The concept of antiphase temperature changes between the North and South Atlantic is discussed. Externally generated abrupt climatic deteriorations owing to explosive volcanic eruptions and variations in solar irradiance are also discussed. Copyright © 2001 Royal Meteorological Society.