Have you heard people talking about El Niño and La Niña? I am here to help explain the differences and what they mean for our planet.
The El Niño Southern Oscillation (ENSO) is one of the most important climatic phenomena on Earth. By influencing global temperatures and precipitation, the ENSO significantly impacts Earth’s ecosystems and human societies. El Niño and La Niña are opposite phenomena, and we cycle through phases of the two. [1]
What is El Niño and La Niña?
An El Niño condition occurs when surface water in the equatorial Pacific becomes warmer than average and east winds blow weaker than normal. The opposite condition is called La Niña. During this phase of ENSO, the water is cooler than normal, and the east winds are stronger. El Niño typically occur every 3 to 5 years, and usually last nine to twelve months. They don’t necessarily alternate: La Niña events are less common than El Niño episodes. El Niño and La Niña are opposite extremes of the ENSO, which refers to cyclical environmental conditions that occur across the Equatorial Pacific Ocean. These changes are due to natural interactions between the ocean and atmosphere and can influence different factors listed below.
Things that are affected by ENSO:
- Sea surface temperature,
- Rainfall,
- Air pressure,
- Atmospheric temperature,
- Natural disasters,
- Ocean circulation.
ENSO’s Impacts
ENSO impacts our planet in different ways depending on which cycle we are in. As it impacts rainfall, this can have a negative or positive impact on crops and food produce, cattle and livestock. If there is too much rainfall, fields are flooded, crops and food production will fail, and livestock might be injured or drown. If there is too little rainfall, this can lead to drought, wildfires, crops and food produce will dry out and fail, and livestock will become dehydrated and underfed. El Niño usually causes increased rainfall, and La Niña usually causes reduced rainfall and drier weather in the Southern Hemisphere, but the Northwestern Hemisphere tends to be colder and wetter than average. Changes in air pressure, ocean circulation and temperatures can have big impacts on marine life. When the ocean’s temperature is too high, coral reefs and marine life can die. This can have a big impact on fishing.
Figure 1: Image of heavy rainfall. [2]
The hottest year on record, 2023, was boosted by El Niño conditions, on top of long-term human-caused climate change, and that warmth has continued into 2024. [3] Between 2020 and 2022, the world experienced an unusually long period of La Niña conditions, which helped keep a lid on global temperatures. El Niño also affects atmospheric circulation patterns, which means there are generally more tropical storms in the tropical Pacific, but fewer in the tropical Atlantic, including the southern US. During La Niña, the reverse is typically true. Scientists have also observed that CO2 levels in the atmosphere increase during El Niño events, possibly as a result of warmer and drier conditions in tropical regions. If plants grow slower due to drought, they absorb less CO2, whilst more wildfires in places like South Asia mean more CO2 is released.
The Intergorvermental Panel on Climate Change (IPCC) concluded there is no clear evidence that climate change has affected these events. Some climate models suggest that El Niño events will become more frequent and more intense as a result of global warming – potentially boosting temperatures further – but this is not certain.
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References
[2] Image of heavy rainfall. https://www.pexels.com/photo/person-riding-a-bicycle-during-rainy-day-763398/ Photo accessed 20/06/2024. Photo credit: Genaro Servín.
