What is El Niño?

Backgrounder

It blows hot. It blows slow. It brings fire and rain, feast and famine. It affects weather around the world. It is called El Niño*. But what exactly is El Niño?

Fishers off the far west shores of South America were the first to notice a dramatic climate change and name it. Usually, the currents in the waters where they fished were cold and flowed from east to west. But, in certain years, the currents flowed in the opposite direction and became very warm. The air became more humid, and large thunderstorms developed. These years were bad for fishing, and it was difficult for the fishers to survive and feed their families. They noticed that this odd weather usually occurred near the Christian Christmas holiday in December, so they called it “El Niño” meaning “the child.”

Around the same time, other areas of the world had unusual floods, hurricanes, or drought. Scientists who studied the weather began to see a pattern in these changes. They found that every three to seven years, the Earth experienced a change in the weather. This change always began in the tropical Pacific Ocean, near the equator. Scientists also believe that this event, now widely known as El Niño, has been happening for hundreds of years.

To understand why El Niño has such a big impact on the environment, it helps to know how the sea and the wind affect each other.

How the sea and wind affect each other

The Earth’s warmest sea water is in a large area of the western Pacific Ocean. Strong winds, called trade winds, blow towards and along the equator in the Pacific. Near the coast of South America the winds are so strong that they create large waves which pull cold water from the bottom of the ocean to the surface. The cold water mixes with the warm surface water. The cold water has lots of nutrients that make the ocean a good place for sea creatures to live.

In a year when El Niño is present, the winds slow down. The reasons are still not clear. When the winds get weaker, they are not strong enough to dredge up the cold, nutrient-rich water from the bottom of the ocean. The water stays warm. Fish and birds begin to disappear.

Something else happens when the winds get weaker. Under normal conditions, the strong winds push the hot tropical waters from east to west. Usually, these waters get pushed thousands of kilometres – as far west as Indonesia.

But in El Niño years, these warm waters drift back to the east, toward North and South America. The air above the ocean gets hot and humid like air above a hot pot of soup. This hot, humid air creates tropical thunderstorms. As the warm water moves east, the world’s biggest thunderstorms move with it. These thunderstorms pump warm air and moisture very high up into the atmosphere. This rising warm air affects other powerful winds that are high up in the atmosphere. These winds, called jet stream winds, carry storms. All the extra moisture in the atmosphere changes the normal course of these high winds. Storms move on different paths and disrupt usual weather patterns around the world.
El Niño and world weather
El Niño can cause floods, drought, hurricanes, fires and other climate problems. The effects of El Niño can be slightly different every time. Sometimes, for example, it brings rain to deserts which normally do not get rain. Sometimes, El Niño causes drought, dust storms or brush fires in areas that are not normally dry. It may even cause harsh ice storms in colder climates. Crops can be severely affected by these climate changes. There are other effects too. For example, flooding can result in swarming mosquitos and the spread of disease.

The effect of El Niño is not always bad. Some places benefit from increased rainfall, and crop yields improve. Unfortunately, it is difficult for scientists to predict accurately when El Niño will happen or how it will affect the weather.

If you are a farmer you will want to get as much information as possible about changes in the weather. Practice methods that save soil and water. By protecting soil and water, your crops will also be protected. Plant a variety of crops – perhaps more than usual. This way there is a better chance that some will survive in the case of dry weather, drought, or heavy rains.