The date of the establishment of the World Meteorological Organisation (WMO) on 23rd March 1950, was named World Meteorological Day. The organization announces a slogan for this day every year. This day is celebrated in all member countries (including Malta). The day is marked with conferences, symposia and exhibitions designed for meteorological professionals and the general public alike. This year’s theme is ‘The Ocean, Our Climate and Weather’. Covering roughly 70% of the Earth’s surface, the ocean is a major driver of the world’s weather and climate. Hence, it also plays a central role in climate change. The ocean is also a major driver of the global economy, carrying more than 90% of world trade and sustaining the 40% of humanity that lives within 100 km of the coast.

Over 90% of the extra heat produced by human action is stored in the ocean. The ocean’s tightknit connection with the atmosphere makes understanding its behavior essential for forecasting weather and projecting climate conditions. The ocean absorbs most of the solar energy reaching the Earth. As the Equator receives much more solar energy than do the Poles, enormous horizontal and vertical ocean currents form and circulate this heat around the planet. Some of these currents carry heat for thousands of kilometers before releasing much of it back into the atmosphere. The ocean warms and cools more slowly than the atmosphere, thus coastal weather tends to be more moderate than continental weather, with fewer hot and cold extremes. Evaporation from the ocean, especially in the tropics, creates most rain clouds, influencing the location of wet and dry zones on land. The enormous amount of energy captured by the ocean creates the world’s most powerful and destructive storms and extreme events such as hurricanes. Since the vast majority of extra heat is stored in the ocean, the atmosphere is warming less quickly than it otherwise would. This should not lull us into inaction, however, as ocean warming only delays the full impact of climate change. Excess heat contributes to sea level rise due to thermal expansion.

Weather forecasters combine ocean observations and knowledge of how ocean–atmosphere interactions shape weather, seasonal and long-term climate and ocean patterns with meteorological observations to forecast the weather

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 Nino and La Niña extremes, 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.