El Niño and the southern oscillation index

Each year, around Christmas time, the waters off the Peruvian coast warm up a little. The locals noticed that at intervals of about 3–6 years the water became warmer than usual, and that this produced flooding rain and poor anchovy catches. They called these events El Niño, which means ‘Christ child’, so named because the events occurred at Christmas time. This Primefact looks at:

• what happens in an El Niño;
• the SOI;
• using El Niño in management decisions.