Here are the key points and takeaways about El nino and La Nina:

  • El Niño Southern Oscillation (ENSO) is a climate pattern that involves changes in sea surface temperature and air pressure across the equatorial Pacific Ocean.
  • ENSO has two extreme phases: El Niño and La Niña. These phases typically last 9-12 months but can persist for several years.
  • Periods with average conditions are referred to as ENSO-Neutral.
  • ENSO events significantly influence global weather patterns. They can contribute to extreme weather events such as droughts, floods, heat waves, and severe storms.
  • El Niño is characterised by warmer than average Pacific sea surface temperatures and weakened trade winds.
  • El Niño can cause:
    • Droughts in regions that typically receive abundant rainfall, such as East Asia and the Amazon rainforest.
    • Increased rainfall in normally dry areas, like western North America.
    • Coral bleaching due to heat stress.
    • Disruption of marine ecosystems due to reduced upwelling of nutrient-rich water.
  • La Niña is characterised by stronger than usual trade winds and cooler than average Pacific sea surface temperatures.
  • La Niña can be thought of as an intensified version of neutral conditions for most regions, with some exceptions.
  • La Niña can lead to:
    • Colder, wetter winters in northern North America and warmer, drier winters in the south.
    • A more active hurricane season in the Atlantic.
    • Increased rainfall in East Asia and Australia.
    • Variable rainfall in Africa, with wetter conditions in the west and potential drought in the east.
    • Lower temperatures and reduced precipitation in central and western Europe.
  • The exact impact of La Niña varies depending on location.
  • The strength of an ENSO event does not always correlate directly with the severity of its effects.
  • Climate change may be intensifying ENSO events, making them stronger and more frequent.
  • Scientists are still studying how climate change will affect the ENSO cycle.