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Climate, Oceans



El Niño, Spanish for the "Christ child," was originally the name used by fishermen to describe a warming of the Pacific Ocean off the coast of Peru that normally takes place around Christmas time. This warming occurs almost every year and lasts a few weeks. In the relatively recent past, however, scientists have discovered this warming can occasionally last for many months, sometimes even longer than a year, and extend westward along the Equator. Today, when we speak of El Niño, we are usually referring to this longer-term event.

El Niño and its opposite phenomenon -- La Niña -- are part of a cycle of repeated warming and cooling of the ocean surface along the Equator in the central and eastern Pacific. The cycle is known as the El Niño Southern Oscillation (ENSO). El Niño refers to the warm phase of the oscillation and La Nina refers to the cool phase. The Southern Oscillation refers to the fluctuation in pressure above the equatorial eastern and western Pacific. During an El Niño, pressure falls in the east and rises in the west. Since air tends to flow from high pressure toward low pressure, this causes winds that normally blow from east to west across the equator to slow down or even reverse direction. The opposite is true during La Niña, when east-to-west winds increase in strength.

Each of these phases influences weather patterns worldwide and results in changes in rainfall that can alter vegetation patterns. El Niño's impacts include changes in global precipitation that sometimes contribute to flooding or drought. Although scientists have a general idea of the regional weather changes that are typically associated with an El Niño, there are many exceptions to the long-term averages. When an El Niño is weak or moderate, it is especially difficult to predict its impacts. For example, the Los Angeles area normally has above-normal rainfall during weak to moderate El Niños, but during the El Niño of 2006-2007, the area experienced its driest year (July 2006-June 2007) on record.

El Niño has also been linked to: disease in South America, increased atmospheric carbon dioxide and methane from fires, harm to coral reefs, an absence of major hurricanes in the North Atlantic, a link to sea ice changes in Antarctica, and economic implications for the United States.



Task: Tim Flannery, one of Australia's leading scientists and author of the "Weather Makers", suggests that conditions may arise in which the world experiences a permanent El Nino state. A select congressional panel has tasked your group with assessing the short- and long-term impacts (both negative and positive) on the Earth system of such an occurrence. The panel is also interested in the potential economic impact on the United States.


Date: 12/6/2012

Scenario Images:

El Nino Southern Oscillation
El Nino is an oscillation of the ocean-atmosphere system in the tropical Pacific having significant consequences for weather around the globe. Among these effects are increased rainfall across the southern portion of the US and in Peru. El Nino, also referred to as ENSO (El Nino Southern Oscillation)has caused destructive flooding, and drought in the West Pacific; it is sometimes associated with devastating brush fires in Australia. Observations of conditions in the tropical Pacific are considered essential for the prediction of short term (a few months to 1 year) climate variations. Go here to compare normal, El Nino and La Nina conditions. Image courtesy of NOAA



ClimateBits: El Niņo (Cycle A)
This short video explains El Niño and its impact on the marine food web. Wind-driven upwelling in the eastern equatorial Pacific normally lifts nutrients to the sunlit surface to fertilize phytoplankton blooms. El Niño disrupts this pattern, causing famine across the marine food web. A big El Niño developed in 2015, shown in satellite images of warmer sea surface temperatures and less chlorophyll - the green pigment in phytoplankton.


NOAA's El Niņo Theme Page (Cycle A)
An excellent site with links to the latest news, numerous articles and resources on El Niño, and links to El Niño climate databases.


El Niņo & La Niņa (El Niņo-Southern Oscillation) ENSO (Cycle B)
Includes the latest information on ENSO, including links to latest official El Niño update.


USGS El Niņo Information (Cycle B)
This portal provides access to United States Geological Survey (USGS) publications related to El Nino, particularly the 2015-2016 El Nino season. There is an introductory article explaining El Nino, followed by a selection of resources on El Nino's damaging effects: floods, landslides, coastal erosion and salt water invasion, and long-term climate variations. There is also an extensive selection of links to non-USGS sites.


Visualizing El Nino (Cycle C)
Links to several NASA visualizations and animations related to El Niño.


Sample Investigations:


Weather Wrecker: Teaching El Niņo (Cycle A)
This 2016 article provides links to NASA education resources related to El Niño.
Difficulty: intermediate


MY NASA DATA El Niņo Lesson (Cycle B)
This MY NASA DATA lesson explores the sea surface height anomaly during the historic El Niño of November 1997. Students correlate real satellite data to local weather.
Difficulty: intermediate


National Geographic's Ocean and Weather: El Nino and La Nina. (Cycle C)
In this lesson students explore the phenomena El Nino and La Nina.
Difficulty: intermediate


Ocean Impacts of an El Nino Event (Cycle C)
Purpose: To examine the relationships among sea surface height, sea surface temperature, and wind vectors in classifying the ocean characteristics of an El Nino.
Difficulty: intermediate




  • Science
    National Science Education Standards - Science Content Standards The science content standards outline what students should know, understand, and be able to do in the natural sciences over the course of K-12 education.
      • Science in Personal and Social Perspectives (Std F)
        • Changes in environments
      • History and Nature of Science (Std G)
        • Science as a human endeavor
      • Physical Science (Std B)
        • Motions and forces
      • Earth and Space Science (Std D)
        • Structure of the earth system
      • History and Nature of Science (Std G)
        • Science as a human endeavor
      • Earth and Space Science (Std D)
        • Energy in the earth system
      • History and Nature of Science (Std G)
        • Science as a human endeavor
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