How does El Niño form?

What is El Niño? How do the extreme weather phenomena caused by El Niño occur?

What is El Niño? How do the extreme weather phenomena caused by El Niño occur?

El Ninjo means the baby boy and is related to another weather phenomenon, La Ninja, which means the baby girl. Both are extreme weather events that result from the natural cycle of weather systems in the tropical Pacific Ocean. In an El Ninjo year, the ocean will be 2-3 degrees warmer off the west coast of South America, but cooler in a La Ninja year.


So-called local winds generally blow across the Pacific Ocean from east to west at the equator. Our worldview, for example viewed on a world map, shows East Asia at the farthest east and the west coast of America at the farthest west.


But the earth is spherical, and in the Pacific Ocean, on the other side of the globe, this world view is reversed. The trade winds in the Pacific Ocean blow from the west coast of South America in the east, to Asia in the west. Ship traffic benefits from this and a journey from South America to Asia takes less time.


The trade winds move the warm surface of the Pacific Ocean to the west, so colder seas rise to the surface on the west coast of South America, while warm surface water causes rain in Indonesia.


The rain causes air to rise in the troposphere and this keeps the local winds going.


Appears at irregular intervals

But every few years, the trade winds subside, and when they no longer push the surface of the Pacific Ocean, the warm surface sea retreats up the coast of South America. This results in so-called El Niño years.


The period between El Ninjo years can vary considerably. El Ninjo is brewing in 2023, but was last in 2018-19. In the latter half of the 20th century, El Ninjo years sometimes only lasted a year, although it was more common for El Ninjo to occur every 2, 3, or 4 years. Often, however, 5, 6 or 7 years have passed and El Ninjo, for example, did not make itself felt from 1926 to 1941.


El Ninjo has a big impact

El Ninjo has a significant impact on the region from Australia to South and North America. In Australia, there are dry seasons, but the weather causes floods in South and North America.


In 1997, the damage caused by El Ninjo was estimated somewhere between 36-92 billion dollars, in addition to which many thousands of people died either from heat stroke or from floods. La Ninja sometimes follows El Ninjo, but not always.


La Ninja also affects the weather in this region, but they do not consist of any reversal of the weather, but the prevailing conditions become more extreme: even less rain in dry areas, while in areas where there is usually a lot of rain, the precipitation will be even more than usual.

El Ninjo causes drought in Australia.

Scientists attach electronic sensors to buoys to precisely monitor the temperature in the Pacific Ocean, and thus can detect when the warm surface sea recedes eastward from Indonesia to South America. Forecasts have not yet become completely reliable, but in the long term they can be of great significance, for example for agriculture.

Climate change strengthens El Niño

A study by Chinese and American scientists  shows that climate change can have a strengthening effect on El Niño. The researchers looked at data from 33 El Ninjo periods and the result shows that after 1978, the source of El Ninjo moved west to the Pacific Ocean, where the sea surface temperature is higher.

This displacement has been followed by three very strong El-Ninjo periods. These were El-Ninjo in 1982, 1997 and 2015. In all cases, great damage was done and temperature records were broken.

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