What You Need to Know about El Niño


This year’s strong El Niño is raising Pacific Ocean temperatures, with consequences for everything from fish to disease. Here are 5 things to look for. (Nat Geo News)

Use our activity to better understand the effects of El Niño and La Niña.

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit.

Discussion Ideas

  • What is El Niño? Watch the short video from NOAA, consult our activity, or read through our short encyclopedic entry for some help.
    • El Niño is a climate pattern that describes the unusual warming of surface waters of the tropical eastern Pacific. “During an El Niño event, sea surface temperatures across a watery expanse often as large as the United States can warm by 1–3° Fahrenheit or more for a period of from a few months to a year or two.”
      • There are different variations of El Niño. One of the most significant is El Niño Modoki. El Niño Modoki events are associated with unusual warming in the central tropical Pacific and cooling in the eastern and western tropical Pacific.
    • El Niño is the “warm phase” of the El Niño-Southern Oscillation (ENSO). The cool phase, La Niña, is characterized by unusually cool ocean surface currents. El Niño and La Niña can be thought of as the ocean part of ENSO, while the Southern Oscillation can be thought of as the atmospheric part of the phenomenon.


  • When is El Niño going to hit?
    • El Niño isn’t a storm that will hit a specific area at a specific time. Instead, the warmer tropical Pacific waters cause slow-moving, long-lasting changes to global atmospheric circulation.
    • According to Nat Geo News, “this particular El Niño isn’t expected to peak until late fall or early winter.”


  • Why is El Niño strongest in the winter?


  • The Southern Hemisphere experiences winter in June-August. Does this mean El Niño is stronger in the Southern Hemisphere at that time?


This terrific map from the good folks at Climate.gov provides a generalized prediction for this year’s El Niño event. To get your ENSO outlook for today, just click here! NOAA is awesome.
Click to enlarge! This terrific map from the good folks at Climate.gov provides a generalized prediction for this year’s El Niño event. To get your ENSO outlook for today, just click here! NOAA is awesome.
  • If El Niño is concentrated in the tropical Pacific, how does it impact weather in other parts of the world?
    • Teleconnections—your geography word for the day. Teleconnections are “large-scale, long-lasting shifts in atmospheric circulation that can affect much of the globe.” The climate scientist in the Climate.gov video explains: “this type of influence from one region to another over large parts of the globe is called a teleconnection.” Here are El Niño’s teleconnections:
      • “During an El Niño event, warm surface water in the Pacific is shifted thousands of miles east of its usual location. The showers and thunderstorms nurtured by convection above this warm tropical water also change location. As the rising motion associated with the convection also shifts eastward, it causes other adjustments in atmospheric circulation, well away from the tropical Pacific. These persistent zones of rising and sinking air can shift into new locations for months, causing prolonged wet or dry conditions and related atmospheric heating anomalies. In turn, the anomalous heating sets up planetary-scale waves in the atmosphere that radiate away from the region, especially into the hemisphere experiencing winter. These are ‘teleconnections’.”


  • Why is the phenomenon called El Niño?
    • The name El Niño originated in the region where one of the phenomenon’s local effects was most recognized, the coast of Peru. We have no real record of what indigenous Peruvians called the phenomenon, but “[b]ecause these events were often observed close to Christmas time, Spanish Catholic immigrants called the phenomenon El Niño (when capitalized, ‘the little boy’ becomes ‘the Christ Child’ in Spanish).”
      • La Niña did not originate in the same way; it was adopted by researchers in the 1970s and 1980s to illustrate the relationship between warming and cooling events in the waters of the eastern tropical Pacific. Some researchers suggested ‘El Viejo’ (the old man) or ‘anti–El Niño’ as alternatives, but La Niña has won out as the standard term.”



  • According to Nat Geo News, what are five signs of El Niño?
    • 1. Unusually strong Pacific storms. “This year has seen eight tropical storms big enough to earn names, double the previous record. On a scale scientists use to add up the energy in storms, this season has also been a whopper, at more than six times higher than usual.”
      • “There’s an upside in the Atlantic, where this hurricane season produced roughly a third of the usual tropical storm activity, according to the National Weather Service’s National Hurricane Center. El Niño years translate into fewer tropical hurricanes there because it strengthens upper-level winds blowing from the west that produce stronger wind shear, tearing apart potential storms.”
    • 2. Flooding and landslides in the Americas. “El Niño wind patterns push tropical moisture towards the Americas, which can translate into heavy rains, flooding and landslides in places like California and Peru.”
      • The historic California drought could make matters worse. A downpour could trigger flash floods if rain falls on ground baked so hard it can’t readily absorb the water.”
    • 3. Drought in southeast Asia and Australia. In Australia, “[l]ast month was the third driest September on record, and the remainder of the year is expected to be warmer and drier than normal, a trend blamed partly on El Niño.” In Indonesia, “[m]onsoon rains usually extinguish the fires, but during the El Niño of 1997 and 1998, dry weather kept fires burning for months into the wet season.”
    • 4. Scrambled fisheries, scrambled economies.
      • “Off the coast of Peru, the tiny anchoveta, a 14-centimeter-long type of anchovy, supports one of the world’s biggest fisheries. But the warm El Niño can decimate populations of these fish, which feed on plankton that grows in cold, nutrient-rich coastal waters. This year, Peru has already closed the anchoveta fishery.”
      • “Meanwhile, warm waters off North America have [already] lured trophy fish such as tuna and marlin to California, north of their usual haunts off the coast of Mexico . . . and may bring species such as yellowtail and bluefin tuna, meter-long Humboldt squid, and the opah, the world’s only known warm-blooded fish. But warmer oceans are bad news for West Coast salmon, at a time when many U.S. salmon runs are already on the Endangered Species list.”
    • 5. Disease outbreaks. “Natural disasters provide breeding grounds for a variety of diseases. El Niño-related flooding is associated with an uptick in cholera, dengue, and malaria in some parts of the world, while drought can lead to wildfires that produce respiratory problems.”



Nat Geo: Hurricane Patricia, More Pacific Storms, and 4 Other Signs of El Niño

Nat Geo: The Ocean and Weather: El Niño and La Niña

Nat Geo: What is El Niño?

NOAA: El Niño—What’s happening today?

The University Corporation for Atmospheric Research: El Niño, La Niña, & ENSO FAQ (this is a fantastic resource—bookmark it!)

Climate.gov: September 2015 El Niño Update and Q&A (this is a fantastic resource—bookmark it!)

Climage.gov: ENSO Blog

NOAA: El Niño

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