El Nino is one of the most predictable climate events on the planet, according the US National Oceanic and Atmospheric Administration, but it also has a way of keeping the climate scientists guessing.
In March the oceanographers predicted the current event could be the weakest on record, but in August the same agency warned it could be the strongest.
Right now it still looks strong, says Nasa’s Jet Propulsion Laboratory (JPL) in Pasadena, California. Using satellite data, meteorologists keep a steady watch on El Nino because it can play out demurely, or it can bring catastrophe. It has been linked to drought and harvest failures on the African continent, devastating fires in the normally moist rainforests of the Indonesian archipelago, both drought and flood in Australia, damaging floods in the Americas, and unusually mild winters in Europe.
Last month, tens of thousands of people had been forced to flee their homes in the border areas of Paraguay, Uruguay, Brazil and Argentina due to severe flooding in the wake of heavy summer rains brought on by El Nino. Paraguay’s national emergencies office has said the flooding is “directly influenced by the El Nino phenomenon, which has intensified the frequency and intensity of rains”.
El Nino is a blister of sea surface heat that every few years floats eastwards across the tropical Pacific Ocean. The shift of warm seas leaves the western Pacific cooler, and both temperature shifts seem to play out in disruption of global weather patterns.
The last great El Nino, in 1997-98, helped to make 1998 the then-warmest year on record - that too was accompanied by a series of devastating events around the world, among them ice storms in North America, floods on the west coasts of the Americas and forest fires in Borneo. It also delayed the monsoon rains in India, warmed tropical waters so severely that coral reefs started to “bleach” and die, and signalled a record-breaking season of typhoons and tropical cyclones in the eastern Pacific.
Although researchers are fairly sure that climate change as a consequence of the combustion of fossil fuels, and the release of greenhouse gases, could make El Nino more frequent, or more devastating, or both, it remains a natural, cyclic event. Climate historians have linked it, with sometimes faltering levels of confidence, to historic events, among them the epidemic of Spanish influenza that claimed millions of lives in 1918.
Sometimes oceanographers watch an El Nino develop, and then fade gently. And sometimes it develops powerfully, with consequences for the rest of the globe. Oxfam has already warned that this time millions could face famine as a consequence.
However, as the rains fail in Africa, Californians - still in the grip of a prolonged and damaging drought - may see a silver lining. In 1997 and 1998 storms slammed into the US west coast, crossed the mountains, drenched Texas and even hit Florida. This time, El Nino may be seen as bringing relief.