Question: What is El Nino and how does it occur and why?

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  1. El Nino refers to the warming of the oceans across the Pacific Ocean and around Indonesia. It occurs in a cycle, coming around every 3-8 years. It causes changes to weather patterns, in particular more cloud over the Pacific Ocean and weaker Easterly winds which in turn leads to Australia experiencing generally drier conditions. Meterologists are constantly monitoring the weather conditions around South America to try and predict when the next El Nino will be.


  2. El Nino is the name we give to a climatic event that originates in the Equatorial Pacific. It is part of climate event system call ENSO (El Nino Southern Oscillation). The Bureau of Meteorology has a good set of webpages describing El Nino and Southern Oscillation (see links 1) and 2) below). The trigger or the “why” is still not fully understood. The main thing to remember is that all global climate systems are connected to together so where is the “start” on circle??

    For a more student friendly version (from link 3) below):

    “El Niño is the Spanish word for the boy-child, a reference to the baby Jesus. The name was given because an El Niño event is characterised by the appearance of warm ocean currents off the coast of South America at Christmas time (the time of the birth of the boy-child Jesus).

    But what does this have to do with Australia? In normal years the cool water over in the eastern Pacific near South America is blown west, and is warmed by the tropical sun along the way. When this warm water reaches the coast of Australia it warms the air, making it rise and creating cumulo-nimbus clouds that bring summer rain.

    In an El Niño year, the circulation across the Pacific weakens, so the upwelling of cool waters is reduced, the warm water stops before it gets to Australia and we have a drought.

    The effects of El Niño reach right around the globe. When we have droughts, large areas of Indonesia, India and Southern Africa also experience dry conditions, Peru gets floods, and parts of North America get very warm.”


    The group I part of work with the effects of ENSO and other climate indices and how they affect biological processes. So the what the climate/weather changes associated withe ENSO are very important. You can imagine the effects of increased temperatures or decreased rainfall can have on living things in the ocean.





  3. As Renee explained, El Nino refers to a period where the Pacific Ocean warms that occurs every few years, and the resulting effect on the weather. Meteorologists study El Nino, because an El Nino weather event can alter the weather so much that it has implications for farmers being able to produce food, and being able to predict when they will happen will allow farmers to plan for the drier weather.

    Here’s a lot more information about El Nino:

    The origin of the term El Nino is really interesting as well! The words “El Nino” are Spanish and translate to ‘the boy-child”. Peruvian fishermen originally used the term to describe the event of warming off the ocean off the South American Coast. It was called this because the ocean warming event happened around Christmas and the name El Nino was in reference to Christmas being the time people celebrate the birth of Jesus Christ.

    PS. It looks like Dirk posted and answer at the same time as me – he’s also provided some great links and information too!


  4. Dirk had a great answer for this one.