Fred Jaicks  Written and compiled by Fred Jaicks


In the Pacific Ocean near the equator, a temporary change sometimes happens in the temperature of the water at the surface of the ocean. When these waters warm up, the change often leads to a worldwide change in climate. Scientists call this weather pattern El Niño. El Niño is Spanish for “little boy.” Fishermen working in the waters off Peru were the first to notice strangely warm ocean water. They noticed this around Christmas time, so they chose the name El Niño because it also means “Christ child.” El Niño usually happens about every two to seven years. Although this mysterious pattern dates back thousands of years, it wasn’t until the past 40 years that scientists began studying El Niño to understand it better. Kids can study El Niño, too, to learn about this fascinating climate pattern.

The Pacific Ocean water near the equator is quite warm thanks to lots of sunlight and high air temperatures in this region. Warm ocean water leads to clouds, which leads to rainy conditions. Typical winds in this region blow toward Australia and Asia, raising temperatures and bringing rain to these continents. When El Niño blows in, the winds become weaker, so the water temperature goes up even more. Scientists know that El Niño is in place by measuring the temperature of the ocean. When the water is between 2 and 10 degrees warmer, El Niño is in effect. As the water temperature goes up, this causes the winds to blow even less. Less wind means warmer water, and warmer water means less wind. The two things feed off of each other and actually make El Niño stronger.

El Niño has an impact on weather around the world. These changes can vary in strength, and they are not always guaranteed. However, weather disruptions are very common in El Niño years. Droughts (a period of dry weather without rain) often happen during El Niño years in Australia and Southeast Asia. Along the west coast of North and South America, flooding often happens. Canada and many parts of the United States tend to have warmer winters in El Niño years. Southern states in the United States will get more storms and wet weather that happens suddenly, forcing locals to quickly hide under a patio umbrella. During El Niño years, fewer hurricanes usually develop in the Atlantic Ocean. Central and South America often see record rainfall during El Niño years. Fishermen in these regions will have trouble catching fish because the fish move to new areas to find cooler water.

La Niña is pretty much the opposite of El Niño. La Niña involves colder ocean temperatures in the Pacific Ocean along the equator. When the ocean water gets colder, La Niña begins affecting worldwide weather. In La Niña years, the United States usually has warmer winter temperatures in southeastern states. States in the north region will have colder winter temperatures. La Niña and El Niño might trade back and forth every year or so, although this does not always happen.

Scientists don’t know why El Niño happens. Every cycle of El Niño is a little different, and these differences make it hard to find a single cause of El Niño. They also make it hard to find any sort of pattern to when El Niño happens, so a guide for predicting El Niño is hard to create. An El Niño lasts between nine and 12 months. It usually starts in the spring, reaches top strength by January, and disappears by the next late spring. Some El Niño years have been very extreme, while others are mild. The winter of 1982 and 1983 was one of the worst El Niño years in history. California and some states in the southern region of the United States had extreme winter storms that caused a lot of flooding and damage.