Scientists unveil new and improved El Niño forecasts
The linked El Niño-La Niña climate cycle on the west coast of Latin America causes periodic bouts of severe damage over thousands of miles. Now scientists can predict more accurately and further ahead when it will happen again.
Climate scientists say they have discovered a better way of forecasting when a periodic and very damaging climate disruption will occur in the eastern Pacific.
The disruption is called an El Niño event, and it is closely linked to severe weather in Latin America and thousands of miles further away, as far as Australia, Africa and North America.
The German-led team says its new forecasting approach will provide not only earlier but also more reliable forecasts of when an El Niño event will happen.
El Niño (“the child” in Spanish, the name given to the phenomenon in reference to the Christ child, because it usually appears around Christmas) and its counterpart, La Niña, are intricately connected with climate change, though theories vary on exactly how they are linked.
The new approach adopted by the researchers, led by the Justus Liebig University in the German town of Giessen, employs network analysis (a technique used for mathematical analysis of a network of interconnected components). They describe it as “a cutting-edge methodology at the crossroads of physics and mathematics”.
To extend their forecasts from six months to a year or longer, the scientists are using something called advanced connectivity analysis, an approach used by complex system science. Building on high-quality air temperature data, they have found it outperforms existing methods.
Quicker and better
Their analysis used data from more than 200 measurement points in the Pacific, from the 1950s onwards, to study the interactions between distant sites that combine to cause the ocean to warm.
Professor Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research and co-author of the study, said:
“Enhancing the preparedness of people in the affected regions by providing more early-warning time is key to avoiding some of the worst effects of El Niño”.
He says the new algorithm the team is using not only extends the period of its forecasts but also enhances their reliability.
Conventional approaches kept on predicting, long into 2012, that there would be a significant El Niño warming in the last year, he said. But the new approach had already correctly predicted as early as 2011 that there would be no such warming.
El Niño is part of a more general disruption of the Pacific ocean-atmosphere system called ENSO (El Niño-Southern Oscillation), which also embraces anomalous cold episodes dubbed La Niña which can inflict severe damage as well. The present study focuses on the warming events alone. But an El Niño year is usually followed by a La Niña one.
Professor Schellnhuber said:
“It is still unclear to what extent global warming caused by humankind’s emissions of greenhouse gases will influence the ENSO pattern.
‘Safety measure’
“Yet that is often included as one of the so-called tipping elements in the Earth system, meaning that at some level of climate change it might experience a relatively abrupt transformation.”
Some data from the Earth’s past suggest that higher mean global temperatures could increase the amplitude of the oscillation, so correct forecasting would become even more important.
Some scientists believe the increased intensity and frequency Рnow every two to three years Рof El Ni̱o and its partner is caused by higher sea temperatures resulting from global warming.
In 1998 scientists from the US National Oceanic and Atmospheric Administration said higher global temperatures might be increasing terrestrial evaporation and adding moisture to the air, so intensifying the storms and floods associated with El Niño.
Another theory is that the Southern Oscillation, the cyclical pattern of which they are both a part, may be acting as a safety valve which releases the pressure that builds up in the tropical oceans.
As global warming raises temperatures, ocean currents and weather systems might be unable to release all the extra heat being stored in the oceans, the theory runs, and so an El Niño occurs to help to discharge the excess heat.
Ludescher et al., (2013) Improved El Niño forecasting by cooperativity detection. Proceedings of the National Academy of Sciences, doi/10.1073/pnas.1309353110