Climate Variability: ENSO

One of the things that I found confusing when I started to get interested in climate change was that the climate is always changing! There are cyclical changes driven by the sun’s internal cycles, by minute changes in the Earth’s orbit and the angle of the Earth’s axial tilt, and then there’s El Nino.

El Nino (Spanish for “The Boy Child” because it often happens around the run-up to Christmas) is a complicated and somewhat predictable (but also somewhat unpredictable) beast. Basically what happens is that a pool of warmer-than-usual water builds up in the western Pacific Ocean, then drifts eastwards towards the Americas, coupled with a reversal of the usual trade winds and changes in rainfall and temperature over large areas. The Met Office has some nice maps that rough out some of the usual changes that occur between El Nino and its opposite, La Nina.

Two of the countries that are most interested in tracking the Pacific Ocean (and which have info that’s readily accessible to English speakers) are the US and Australia. Both publish monthly updates on what ENSO (the El Nino/Southern Oscillation) is up to – NOAA has its data here and the Australian Bureau of Meteorology has its info here.

For the UK, there’s not a lot of concern with El Nino directly impacting our weather, but ENSO does affect countries that we do business with, dictating such important factors as the timing and intensity of the Indian Ocean monsoon season, drought in Australia and rainfall in California/Central/South America. These global patterns have a knock-on effect on crops that we import – such as sugar cane and citrus fruits from the Americas, North and South, or rice from the Indian sub-continent.

At the moment there’s a “neutral” ENSO condition in the Pacific, meaning neither El Nino nor La Nina is in play, but there does seem to be an increasing likelihood that El Nino will be back later in 2014 – which means that the already extraordinary drought in Australia may intensify, but that California’s current drought may break and, if previous El Nino seasons are a guide, that Central America may see severe floods due to heavy rains.

If we do see an El Nino develop, we may well also see global average temperatures for 2014 reach new heights, since El Nino is associated with higher global average temperatures. This is natural climate variation at work, not anthropogenic climate change, but still worth watching!



One thought on “Climate Variability: ENSO

  1. Pingback: El Nino, Drought and the Price of Wheat… | Adapt, Mitigate, Survive

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