Long-term weather forecasts are suggesting 2014 might be the hottest year since records began.
An El Niño occurs when warm water buried below the surface of the Pacific rises up and spreads along the equator towards America. For nine months or more it brings rain and flooding to areas around Peru and Ecuador, and drought and fires to Indonesia and Australia. It is part of a cycle called the El Niño-Southern Oscillation.
It is notoriously hard to make a prediction before the "spring barrier" as to whether there will be an El Niño in a given year.
But now a model aimed specifically at predicting El Niño seems to be able to sift through the noise by examining a previously-unexplored feature of Pacific weather.
Previous predictions have relied on full climate models. Rather than using this traditional approach, Armin Bunde of Justus Liebig University in Giessen, Germany, and his colleagues looked at the strength of the link between air temperature over the equator and air temperature in the rest of the Pacific. The records showed that, in the year before each El Niño, the two regions became more closely linked, meaning their temperatures became more similar than at other times.
The team also found that, once these atmospheric links reached a critical strength, around 75 per cent of the time an El Niño developed within a year (PNAS, doi.org/rdn).
Now they say the threshold was crossed in September 2013. "Therefore, the probability is 0.76 that El Niño will occur in 2014," says Bunde. In other words, there is a 76 per cent chance of an El Niño this year.
As a result of climate change 2014 is likely to be one of the hottest years on record. If El Niño does develop this year, it will make 2014 even hotter – maybe the hottest ever. But since El Niño normally straddles two calendar years, it might give 2015 that title.
An increasing number of climate models are now predicting El Niño this year too. It is unclear whether it will be an extreme El Niño like the 1998 event, which is thought to have killed tens of thousands.