The El Niño-Southern Oscillation and the North Atlantic Oscillation are by no means unique. Similar phenomena of greater or lesser intensity, varying over periods of several years, can be observed across the oceans of the globe.
fig 1. Pacific Decadal Oscillation (Credits University of Washington)
Extended time series of satellite data now allow us to study ocean variations over several years. Today, the Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO) and El Niño Southern Oscillation (ENSO) are well documented. The next step will be to predict these phenomena. To achieve this goal, we need to gain a better understanding of how they might be interacting and how they are affected by other ocean and atmospheric variations. Continued monitoring by a permanent series of ocean-observing satellites should yield vital clues.