Major Oscillations

Understanding the Earth's climate and forecasting its weather are amongst modern science's greatest challenges. Climate and weather are largely determined by the complex and interdependent interactions between the oceans and the atmosphere. Although these interactions are responsible for regular, familiar weather and climate patterns, they also experience variabilities that result in irregularities, or anomalies, in climate and weather patterns. Variability in the climate system may be natural or anthropogenically induced. Anthropogenically induced climate variability is where the climate system experiences changes as a result of human activities: for example, although fossil fuel burning and deforestation have altered the natural climate system in ways that are not yet fully understood, they do contribute to climate variability as they are strongly linked to globally rising temperatures, increases in severe weather events, and an ever-shifting and currently unpredictable pattern of droughts, floods, famine and disease. However there are also naturally occurring variability in the Earth's climate system, such as 'major oscillations'.

Major oscillations in the climate system, also known as 'climate modes', occur when the normal circulation patterns of the coupled ocean-atmosphere system change abruptly. These deviations can be driven by alterations in atmospheric pressure systems, precipitation patterns, or ocean circulation patterns, and the effects range from changes in normal weather patterns to disturbances in the ocean's normal upwelling patterns and food-web cycle. Probably the most famous major oscillation is the El Niño/Southern Oscillation, although climate modes have been identified in nearly every ocean basin region, and normally exhibit a see-saw pattern, swinging from one extreme to the other, over decadal or longer timescales.

Variabilities in the global climate system produce effects that manifest themselves on a timescale that ranges from seasons to millennia. These effects do and will continue to affect the conditions of life on Earth, thus monitoring and studying climate variability is important for humanity. Moreoever, although the oceans' role in climate and climate variability has long been recognized, understanding the natural, anthropogenic and regional expressions of this role is just beginning and requires the combined efforts of meteorologists, oceanographers, biologists, glaciologists, and geologists.