In addition to influencing the geography of the planet’s climate zones, the ocean causes the climate to vary over periods of weeks to decades through regular oscillations. Examples are the El Niño Southern Oscillation (ENSO) - which includes both El Nino and La Niña extremes - in the tropical Pacific, the Indian Ocean Dipole and the North Atlantic Oscillation. Oscillations are caused when changing patterns of sea-surface temperature, atmospheric pressure and wind produce climatic periods that are warmer or cooler, or wetter or drier, than normal.
With improved monitoring of the ocean and atmosphere and enhanced scientific understanding, scientists can increasingly identify and predict these oscillations – and thus the climate and weather. WMO Regional Climate Centres and Regional Climate Outlook Forums use this knowledge to produce consensus seasonal climate forecasts.