What are 'El Nino' and 'La Nina' all about?

Drainage system at Kwa Rhonda Estate in Nakuru city in September 2023. [Kipsang Joseph, Standard]

The El Nino-Southern Oscillation (ENSO) is a significant climate phenomenon that influences weather patterns across the tropics. Alternating irregularly between warm El Nino and cold La Nina phases, it brings about shifts in ocean surface temperature and disrupts wind and rainfall patterns.

While El Nino events usually last for a year, La Nina can persist for two consecutive years or even longer, leading to prolonged and aggregated impacts such as wildfires and flooding.

A study by researchers from China, Australia, and the U.S. shows multiyear La Nina events are expected to increase under global warming. In the study, published in the scientific journal Nature, researchers reported a significant increase in the projected frequency of multiyear La Nina events over a 100-year period, raising concerns about potential consequences for countries like Kenya.

Dr JIA Fan from the Institute of Oceanology of the Chinese Academy of Sciences, co-corresponding author, explains that under current climate conditions, a strong El Nino induces a negative North Pacific Meridional Mode-like response, leading to a La Nina in the subsequent winter with extensive sea surface temperature and easterly wind anomalies.

With global warming, El Nino becomes more efficient at triggering multiyear La Nina due to enhanced tropical-subtropical interaction, leading to more frequent events.

The consequences of increased multiyear La Nina events could be far-reaching for countries like Kenya. With the heightened frequency and duration of La Nina, the country may experience heavier and more prolonged rainfall, leading to flooding in various regions and causing damage to infrastructure.

This could result in the displacement of communities and disruptions in transportation and communication networks.