Philander, S. G. H., and N-C. Lau, 1988: Predictability of El Niño. In Physically-based Modelling and Simulation of Climate and Climatic Change, Part II, Dordrecht, The Netherlands: Kluwer Academic Publishers, 967-982.

Abstract: Low-frequency variability on timescales on the order of a year and longer in both the tropical oceans and atmosphere is caused primarily by variations in the boundary conditions, the surface winds in the case of the oceans and the sea surface temperature in the case of the atmosphere. The variability of each medium can therefore be simulated for indefinite periods provided the boundary conditions are specified. Interactions between the ocean and atmosphere are unstable and can amplify perturbations thus causing the Southern Oscillation and El Niño. The predictability of this variability is determined by the growth rate of unstable disturbances and depends on the degree to which the initial state of the ocean is in nonequilibrium with the winds. Calculations with a relatively simple coupled model indicate that predictability may be longer than a year.