What Is El Niño and Why Does It Matter?

pacific warming event alters weather patterns worldwide

By Jonny Lupsha, Wondrium Staff Writer

Extreme weather events can cause effects thousands of miles away. Earthquakes that cause tsunamis have devastating consequences far from their points of origin. What does El Niño do to the Earth?

El Nino diagram
An El Niño global weather system can result in extreme weather patterns worldwide throughout the year. Photo by Fred the Oyster / Wikimedia Commons / Public Domain

Hurricanes, earthquakes, and tsunamis are just three examples of extreme weather events that wreak havoc, far and wide. They may lead to death, injury, and destruction hundreds or even thousands of miles away from where they initially occur. However, even extreme weather events are affected by global weather events like climate change.

An example of a global weather event is El Niño, which translates from Spanish as “little boy.” The World Meteorological Organization recently reported that the odds are increasing of an El Niño occurring this fall. In his video series The Science of Extreme Weather, Professor Eric Snodgrass, Director of Undergraduate Studies for the Department of Atmospheric Sciences at the University of Illinois at Urbana–Champaign, defines the phenomenon and its consequences.

What Does El Niño Mean?

The term El Niño was first coined by Peruvian fishermen hundreds of years ago when they noticed occasional warming in the waters of the Pacific.

“The periodic Pacific Ocean warming events often peak in intensity during the Northern Hemisphere winter, usually in December,” Professor Snodgrass said. “El Niño refers to Jesus Christ, the messiah of the Christian faith, because of its timing with the Christian holiday of Christmas where the birth of Christ is celebrated.”

Whenever a strong El Niño forms, it affects weather conditions on a global scale. As one develops, regular trade winds, which usually blow from east to west, don’t flow normally. They can be weakened, stopped, or even reversed by an El Niño. Keep in mind that Earth’s atmosphere and oceans are a coupled system, their air affecting each other. El Niño disrupts global circulation patterns and the ways in which warm and cool air flow among this coupled system.

“El Niño events end when both the atmospheric and oceanic circulations return to the global patterns,” Professor Snodgrass said. “High air pressure builds in the east, and low air pressure forms in the west, and the trade winds resume their normal westward flow.”

However, El Niño’s effects are far more than just which direction the wind is blowing.

What Does El Niño Do to the Weather?

Once an El Niño event has occurred, weather patterns for the entire calendar year can change. Peru and Australia are the two most obviously impacted areas, though this disruption in global air circulation is felt around the world. For example, the number of winter weather events in North America in the 2009-2010 season is also a sign of an El Niño.

“During an El Niño, Lima can receive an entire year’s worth of rainfall in a single afternoon,” Professor Snodgrass said. “Flooding, landslides, and mudslides occur frequently during El Niño. [These] events are notorious for causing major flooding in Peru.”

However, it causes different events in other places. Indonesia and Australia often suffer major drought while Lima gets soaked. Similarly, the change in winds caused by El Niño can create a perfect breeding ground for tropical storms. A normal hurricane season in the East Pacific may have 15 named storms, but the 2015 East Pacific hurricane season had 28.

“A normal hurricane season in the East Pacific will have seven hurricanes, three of which become major hurricanes of Category 3 status or higher,” Professor Snodgrass said. “2015 had 15 hurricanes, 10 of which became major hurricanes.”

The Science of Extreme Weather is now available to stream on Wondrium.

Edited by Angela Shoemaker, Wondrium Daily