[Statement over El Nino, La Nina and the austral oscillation phenomena] | Le point sur les phenomenes d'El Nino, de la Nina et de l'oscillation australe
2001
Dewitte, O. (Universite de Liege, Sart Tilman (Belgium). Institut de Geographie. Departement de Geographie physique)
In recent years the meaning of ® El Nino ¯ has been the subject of much confusion in the media. Usually this term has been used, particularly in 1997, in relation to the heavy rainfalls in western South America and California, and droughts in Australia and Indonesia. However the phenomenon of El Nino is part of a much larger element of the world climate system known as the El Nino- Southern Oscillation (ENSO). El Nino is now understood to be one phase of a natural mode of oscillation - the warm phase -, La Nina is the complementary phase - the cold phase. The present development of networks in situ and remote sensing measurements allow to better understanding the ENSO events as an enormously complex atmosphere-ocean feedback process that is often erratic and extreme. ENSO recurring is typically 2-7 years, and is modulated on interdecenial variations. ENSO affects almost two thirds of our planet; the last El Nino phenomenon, of 1997-1998, is one of the most important of the century with the one of 1982-1983. The studies by dynamical models and the forecasts are very important particularly in the context of global warming. The analysis of proxy data shows that ENSO is a natural mode of oscillation that exists as today form since 5 000 years. Recent advances in observational and theoretical studies of El Nino have shed light on controversies concerning the possible effect of global warming on this phenomenon over the past few decades and in the future
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