The science behind El Niño

What drives the climate phenomena with the power to impact weather across the globe.

Typical weather patterns in the U.S. during El Niño years. However, these trends can vary significantly across different El Niño events.  Photo credit: The Weather Channel
Typical weather patterns in the U.S. during El Niño years. However, these trends can vary significantly across different El Niño events. Photo credit: The Weather Channel

Forecasters are predicting an especially strong El Niño effect this year. As a Michigan State University Extension educator with Michigan Sea Grant, I have been fielding several questions on the potential impact of El Niño and the science behind this influential climate phenomena.

What exactly is El Niño?

El Niño occurs when the waters of the tropical eastern Pacific Ocean are unusually warm. This happens periodically (every 2 to 7 years). The warmer water temperatures impact trade winds and storm patterns with important consequences for weather across the globe.

La Niña is the opposite phase of this climate phenomena in which waters of the eastern Pacific Ocean are colder than usual. Together El Niño and La Niña form the El Niño-Southern Oscillation (ENSO) cycle.

Where does the name El Niño come from?

The name El Niño originated among 17th century South American fishermen who realized that this periodic warming typically reaches peak strength around December. El Niño means “little boy” or “Christ child” in Spanish. 

How does El Niño impact global weather patterns?  

One of the difficulties in effectively predicting the full impacts of El Niño is that no two El Niño events are exactly alike. Past El Niño events have varied significantly in strength and have resulted in very different global weather patterns. Generally speaking El Niño is associated with warmer-than-average temperatures and drier-than-average conditions in the Great Lakes region. However, these are only general trends and far from set in stone. While the specific consequences of El Niño in a given year are highly unpredictable the phenomena is certain to influence storm patterns, ocean currents, trade winds, and marine fisheries across the globe for significant periods of time.        

How will climate change impact El Niño?

The potential impact of climate change on future ENSO cycles is still unknown. Availability of reliable data from past El Niño events is limited and climate models have produced conflicting results.

A recent study from the Georgia Institute of Technology and Scripps Institute of Oceanography examined core samples from coral in the Pacific Ocean to better understand historic variations in El Niño intensity. By studying the ratio of oxygen isotopes in coral samples researchers were able to determine what temperature and precipitation changes the coral were exposed to over time. They found much higher intensity and variability of El Niño events in the 20th century compared to previous eras.  

This study produced a wealth of new data on historic El Niño fluctuations. However, much more research is still needed before a definitive link can be established between climate change and changes in the ENSO cycle.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.

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