Hold onto your ice lollies. Long-term weather forecasts are suggesting 2014 might be the hottest year since records began. That鈥檚 because climate bad-boy El Ni帽o seems to be getting ready to spew heat into the atmosphere.
An El Ni帽o occurs when warm water buried below the surface of the Pacific rises up and spreads along the equator towards America. For 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 .
It is notoriously hard to make a prediction before the 鈥渟pring barrier鈥� as to whether there will be an El Ni帽o in a given year. 鈥淭he El Ni帽o-Southern Oscillation cycle more or less reboots around April-May-June each calendar year,鈥� says from the Bureau of Meteorology in Melbourne, Australia.
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The problem is that there is so much background variability in the atmosphere and ocean that it is hard to see any signal amidst the noise, says from the CSIRO, Australia鈥檚 national research agency in Melbourne. 鈥淓ven if there is a developing El Ni帽o, it is hard to predict.鈥�
Links in the air
But now a model aimed specifically at predicting El Ni帽o 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 Ni帽o, 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 Ni帽o developed within a year (). 鈥淭here is certainly a correlation between the cooperative mode in the atmosphere that we measure and the onset of an El Ni帽o event,鈥� says Bunde. Nobody knows why.
Now they say the threshold was crossed in September 2013. 鈥淭herefore, the probability is 0.76 that El Ni帽o will occur in 2014,鈥� says Bunde. In other words, there is a 76 per cent chance of an El Ni帽o this year.
As a result of climate change 2014 is likely to be one of the hottest years on record. If El Ni帽o does develop this year, it will make 2014 even hotter 鈥� maybe the hottest ever, says Cai. But since El Ni帽o normally straddles two calendar years, it might give 2015 that title. 鈥淚t is possible, but not a sure thing. It can be tipped over either way by other variability.鈥�
An increasing number of climate models are now predicting El Ni帽o this year too. It is unclear whether it will be an extreme El Ni帽o like the 1998 event, which is thought to have killed tens of thousands. But Cai thinks an extreme El Ni帽o is unlikely because longer-term variability in the Pacific鈥檚 weather is suppressing it.
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