El Niño/Southern Oscillation (ENSO) is a naturally occurring large-scale climatic phenomenon involving fluctuating ocean temperatures in the central and eastern equatorial Pacific, coupled with changes in the overlying atmosphere (e.g. sea-level pressure, cloudiness and winds). El Niño and La Niña are the oceanic components, while the Southern Oscillation is the atmospheric counterpart, thus giving rise to the term ‘El Niño/Southern Oscillation’ (ENSO). ENSO occurs in irregular cycles of two to seven years, and presents three phases: El Niño, La Niña and a neutral phase.