A forecasting technique created by Israeli and German researchers doubles the advance warning time for the outbreak of violent weather systems called El Niño – and predicts that one of these storm systems will develop and hit towards the end of 2020.
Until now, El Niño couldn’t be predicted more than six months ahead of time.
By nature, forecasts involve uncertainty. However, based on their method, the probability of El Niño in late 2020 is around 80 percent. "But that’s pretty significant,” says Hans Joachim Schellnhuber, director emeritus of the Potsdam Institute.
The researchers' model proved itself last year, the scientists say: In 2018 they predicted there would be no El Niño in 2019. Indeed, there was not.
The ground-breaking algorithm was created and revealed six years ago by a consortium of scientists from Justus Liebig University Giessen, the Potsdam Institute for Climate Impact Research and Bar-Ilan University. It takes time to test a weather model.
El Niño is often referred to as some sort of aberration in weather, but given that it occurs every so many years, it’s not abnormal, just rare. It arises from a situation where the sun warms the Pacific Ocean off the South American coast more than half a degree above a five-month average. When that happens, an El Niño is declared, Havlin tells Haaretz.
The upshot is worldwide havoc to wind currents and stormy weather. El Niño often features flooding in Ecuador and Peru, torrential rain or intense drought in the rest of South America and elsewhere in the world, and extreme temperatures both hot and cold. “It is the biggest climatic system that affects the whole world,” Prof. Shlomo Havlin of Bar-Ilan University says.
Also, it typically hits late in the year - around Christmas.
If there’s one area that is relatively spared the wrath of “the Christ child” as the weather system is known, it’s the Mediterranean basin, which means that Israel is largely spared. It bears adding that not much research has been done on how exactly El Niño does affect the Med region, Havlin says, but its local effect isn’t dramatic.
The methodology change is just in time. El Niño’s occurrence is erratic. If until now it would happen every two to seven years, global warming is expected to increase its frequency and intensity, making it all the more important to have long advance notice.
Why would it happen more under conditions of climate change? “In a warming world there is more heat being trapped every year, so there is more heat in the oceans to fuel El Niño events,” the Climate Signals organization explains.
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Like prophecy, weather forecasting is for fools. Think how reliable forecasts of rain have been in Israel this winter. Not very, and that’s one day or week to the next. How did the researchers manage to double their advance warning periods for a whole weather system?
Other models predicting El Niño are based on running climate models that forecast water temperature at one place, such as off South America's Pacific coastline, Havlin says. If the prediction is that the water has been more than half a degree warmer over five months, an El Niño warning will be declared.
The team measured air temperature off the South American shores and around the world. When they crunched the data by network analysis, they discovered strong correlations between the South American water temperature level and weather patterns around the world, a year in advance.
The researchers used a network of atmospheric temperature data in the tropical Pacific consisting of 14 grid points in the equatorial “El Niño” core area, and 193 points in the Pacific outside this core area, Armin Bunde says. As long as a year before the eruption of an El Niño, the connecting effect between global air temperatures and the core area strengthens significantly.
So, they predict an El Niño late this year. No other models are capable of predicting one so far in advance.
Their algorithm also correctly predicted the last two El Niño events, in 2014 and 2018, more than a year beforehand.
Such long advance notice is nice for fishermen: among other things, the weather pattern decimates large fish populations off the Peruvian coast. Advance knowledge is absolutely crucial for farmers, who need to plan their crop management well in advance and find it quite useful to know that the weather in a given year will not be their friend.