1In the 1980s, meteorologists were unequivocal: the weather was impossible to predict more than one or two weeks in advance. Ten years later, they were proved wrong by climatologists who managed to predict certain weather anomalies several months in advance. Getting to this point required the observation and understanding of a phenomenon about which practically nothing was known: El Niño. IRD played a significant part in this international success story, collecting numerous observations thanks to merchant vessels, oceanographic campaigns, and contributing to the installation of “TAO”, a network of instrumented buoys distributed across the surface of the Pacific since the 1990s.

Northern Peru, destruction caused by El Niño.

2These observations gradually revealed the secrets of El Niño, a major climate phenomenon linked to interactions between the ocean and the atmosphere. In the Pacific, the winds usually blow from east to west, causing the upwelling of deep, cold water, rich in nutrients, near South American shores, and warmer water conducive to heavy rainfall on the other side of the Pacific. This balance is frequently upset, resulting in El Niño events accompanied by droughts in Australia, unusually warm and low-productivity waters in Peru, or tropical cyclones in French Polynesia.

••• Research to gain a better understanding of the multiple dimensions of El Niño •••

False-colour satellite image of an El Niño episode.

3IRD researchers contributed to demonstrating the predominant role of the Central Pacific region in the creation of the “snowball effect” resulting in the development of an El Niño episode. This research, published in the late 1990s, shed light on the ocean-atmosphere interactions responsible for the development of El Niño.  IRD is still working on the multiple dimensions of this climate phenomenon, more specifically on the two categories of El Niño, distinguishing between extreme events with devastating impact and other, more frequent events confined to the Central Pacific region. IRD was also instrumental in showing that the most extreme El Niño episodes could become far more frequent by the end of the 21^st century. In addition, the Institute acts as a driving force in the ongoing remodelling of the global Pacific ocean observing system.

“The El Niño phenomenon has significant effects in Peru, as a result of which it raises numerous scientific issues regarding its dynamic, mechanisms and, more importantly, its predictability in the eastern Pacific. El Niño generates extreme events, with devastating consequences for people and infrastructures, which notably affect farming activities and fisheries in Peru. As a researcher working in this field, I had the good fortune to work with international experts in Peru, with the support of IRD, and to make the most of IRD’s student expatriation and training model which, in addition to producing scientific publications, enables the application of newly gained knowledge to all activities…”
Ken Takahashi, head of the National Meteorological and Hydrological Service, Peru