News from the Columbia Climate School

El Niño Begins to Dissipate

Though weak El Niño conditions still exist, it appears that the climatic phenomenon that developed over the course of last summer has finally begun to dissipate. As reported earlier, El Niño is the name given to sustained sea surface temperature (SST) anomalies greater than 0.5°C across the central tropical Pacific Ocean. It is the warm phase of the El Niño Southern Oscillation (ENSO), a global coupled ocean-atmosphere phenomenon involving the tropical eastern and western Pacific Ocean.

Because climate in many regions of the globe is strongly influenced by tropical SST, El Niño phases bring enhanced climatic predictability. This fact is evidenced by the higher-than-average skill shown in IRI forecasts over the past season. It also underlies assumptions about the use of climate forecasts to allow people to prepare for and thus mitigate the socioeconomic impacts of climate variability, making years of El Niño extremes less costly in terms of life and property.

Enhanced predictability is also associated with La Niña, the cool phase of ENSO, when sea surface temperatures in the equatorial Pacific are more than 0.5 °C below normal. At this point, however, it’s still not clear whether the current El Niño will be followed by a La Niña, or if climatic conditions will become neutral, making prediction is a bit more difficult. Both models and historical analogs show a range of possibilities for the coming months, so forecasts are split.

At the International Research Institute for Climate and Society (IRI)’s Climate Briefing, presented earlier today, Lead Forecaster Tony Barnston predicted a greater-than-50% chance of neutral conditions developing before June. Barnston also showed an above-average chance of La Nina beginning in August, though he’s careful to point out that a great deal more will be known about the likelihood once we pass the spring predictability barrier. For more on evolving climate conditions, check out IRI’s ENSO quicklook page here.

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