A warm tongue of water stretches along the equatorial Pacific, and within weeks, Peru sees downpours while Australia's pastures dry up. This is El Niño, a natural conductor who, at critical moments, makes only a few orchestra members play, but much louder. Scientists wanted to understand why his cues are heard not everywhere, but only in certain spots.
Researchers built a climate network, a map where points on the planet are linked by threads if their weather changes similarly. Each thread ran from the warm ocean tongue (57 points) to any other point on the globe. It turned out that during El Niño and its cold counterpart La Niña, these threads do not spread evenly but gather into cords. The number of points receiving the cue decreases, but the cue itself sounds far stronger.
Previously, it was known that El Niño affects distant countries, but it was unclear how concentrated that influence is and how it varies from one event to the next. Now it is clear: during events, the impact becomes stronger but reaches fewer places, and those places differ each time. This way of looking only at the threads emerging from the warm tongue can be applied to rainfall or winds, to warn in advance where drought or flooding might occur. The conductor does not always wave his baton the same way, but now we can hear whom he is calling this time.
During the strong El Niño of 2015–2016, one of the strongest since 1948, researchers were able to confirm most of the affected regions using data from previous events only, demonstrating the method's predictive potential.
In Kim Stanley Robinson's novel 'Forty Signs of Rain', climate networks and chaotic ocean dynamics play a key role in understanding abrupt climate change, echoing attempts to capture El Niño teleconnections.