Wednesday March 1, 2023

The Conversation

It was anchovy fishermen in Peru who first noticed and named El Niño events in the tropical Pacific hundreds of years ago. Their catches would fluctuate and the largest declines were seen near Christmas when the ocean was at its warmest – they called it El Niño de Navidad, the boy of Christmas.

With a larger network of observations and some inspired statistical analysis, it became apparent that this decline in fish stocks was part of a Pacific-wide phenomenon including changes in the ocean and atmosphere. This was ENSO, the El Niño-Southern Oscillation.

As part of this analysis it became clear that during El Niño events the Pacific was typically warmer than usual in the east, colder in the west, and the trade winds blowing from east to west were weaker. What also became clear was that there were other times when the winds were stronger and the east was colder and the west was warmer. These periods were named La Niña – the girl – in a nod to their opposite characteristics to El Niño.

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