The discovery of this cycle is not trivial

It is a new barrier may just fall into the understanding of the major terrestrial climate sets. A group of young researchers from the Institut de recherche pour le développement (IRD) led by Takeshi Izumo of the Japanese Agency for science and technology marine and terrestrial stationed in Goa, French-Japanese suspected the "dipole" in the Indian Ocean, an oscillation of the temperature of surface water in part Equatorial of the region, to be responsible for the onset of El Niño to thousands of kilometres to the East, the waters of the tropical Pacific. In support of their argument, published in the journal "Nature geoscience", the results delivered by a model statistical prevention of their invention covering a period from 1981, date of early marine observations and reliable satellite, 2008. The authors concluded: "an increase in temperatures in the Eastern Indian Ocean above four to five months the beginning of the El Niño phenomenon with only 5 chance that the relationship is the fact of chance", explains Matthieu Lengaigne, researcher IRD in the laboratory of Oceanography and climate (Locean).

Best forecast

El Niño Southern Oscillation (Enso) is the more energy the planet climate phenomenon identified in 1924 by the British Gilbert Walker. It is known that he is bound to a displacement of masses of warm water from West to East across the tropical Pacific. Normally, the warm waters of this ocean are contained by the trade winds in the West of the region. When the winds weaken, they drain eastward, which initiates the hot phase of Enso, El Niño, with much of the world climate consequences: drought in southern Africa and Indonesia, flooding and collapse of marine biodiversity in Latin America, waves of cold in Europe... Conversely, the hardening of the trade winds causes upwelling of deep cold waters to the East, a less violent phenomenon known as La Niña. Without that it knows why, the other fire so irregularly every two to seven years. It was to the 20th century that 17 episodes La Niña, moderate to strong, and 25 El Niño same scale.

That suggests the Franco-Japanese team, it is that the onset of El Niño events - La Niña originates in the Indian Ocean. The Indian Ocean dipole is a similar phenomenon to El Niño, but with less dramatic manifestations remain concentrated in the region. His influence is evident during the boreal winter by causing a sudden decrease in easterly winds in the central Pacific in the end of its negative phase. This "leads the movement to the East of the Western tropical Pacific warm pool", finds Matthew Lengaigne. "We therefore have good reason to suspect that the atmospheric circulation binds strongly the two oceans."

Warm surface water accumulated in the West would be more learned and therefore elapse eastward, resulting in the formation of an El Niño episode which would reach its peak approximately fourteen months after that of the Indian Ocean dipole. In the same way, the opposite phase of the dipole would be the prelude to La Niña, which, according to the scenario proposed by the researchers, would in turn a negative Indian dipole, and so on with varying degrees of intensity.

The discovery of this cycle is not trivial. International agencies (through the network of buoys TAO) monitor the evolution of the tropical Pacific Ocean. But these observations allow that approximate forecast eight to ten months before the peak of El Niño, to December. But statistically, Enso participates to 30 in the Indian monsoon intensity including. By winning several months on the prediction of the phenomenon, climatologists believe able to moderate the socio-economic consequences in certain regions of the world. In Australia, for example, farmers could react to the announcement of a drought in adapting their seedlings and using crops requiring less water.

Frequency accelerated

This work will also open a new piece of research in the understanding of the great disruptors of climate. This winter, other scientists from the IRD (Institute of research for development) have highlighted that climate change would lead to more frequent El Nino events "Modoki", cousin to the specific impact in the central part of the equatorial Pacific that causes severe droughts on the Australia and India by disrupting the monsoon. "By the end of the 21st century, explained the scientists, this type of event could occur five times more often. It will not change, but it will at least know who is responsible for. "Consolation.