Volcanic eruption linked to El Niño

Researchers at Rutgers University have discovered that large volcanic eruptions can prompt El Niño events.

The El Niño Southern Oscillation (ENSO) occurs every three to seven years and usually peaks at the end of the calendar year. It causes worldwide impacts on the climate by altering atmospheric circulation. Using sophisticated climate model simulations, researchers showed that El Niño tends to peak the year after large volcanic events such as the 1991 Mount Pinatubo eruption, in the Philippines.

Professor Alan Robock, co-author of the study published in Nature Communications, said: “We can't predict volcanic eruptions, but when the next one happens, we'll be able to do a much better job predicting the next several seasons, and before Pinatubo we really had no idea. All we need is one number ­– how much sulphur dioxide goes into the stratosphere – and you can measure it with satellites the day after an eruption."

These enormous eruptions pump millions of tonnes of sulphur dioxide into the stratosphere, forming a cloud of sulphuric acid. This cloud reflects solar radiation and reduces the average global surface temperature. Studying sea surface temperature data since 1882 showed that large El Niño like patterns have followed four out of five large eruptions including Pinatubo.

The study focused on Mount Pinatubo because it is the largest and best-documented eruption in recent history able to be accurately evaluated. It is believed to have ejected around 20 million tonnes of sulphur dioxide. Climate model simulations showed that Pinatubo-like eruptions tend to shorten La Niñas (a climate pattern describing the cooling of ocean waters along the tropical west coast of South America), lengthen El Niños and lead to unusual warming during neutral periods.

If there was a big volcanic eruption, Robock said he could make predictions for seasonal temperatures, precipitations and the appearance of El Niño next winter. He said: “If you're a farmer and you're in a part of the world where El Niño or the lack of one determines how much rainfall you will get, you could make plans ahead of time for what crops to grow, based on the prediction for precipitation.”