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El Niño
References & Edit History Quick Facts & Related Topics
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How strong El Niño conditions develop Map of the tropical Pacific Ocean highlighting the four ENSO (El Niño-Southern Oscillation) regions: Niño 4, Niño 3.4, Niño 3, and Niño 1+2. The regions are marked as colored rectangles along the equator from near Australia to the coast of South America, illustrating key zones used to monitor El Niño and La Niña climate events. Diagram of the equatorial Pacific Ocean showing El Nino conditions, with weak trade winds, increased rainfall over South America, increased convection, a deepened thermocline, and suppressed upwelling. Two diagrams compare coastal upwelling during normal conditions and an El Nino event. The top shows strong upwelling with nutrient-rich water and high plankton near the coast, while the bottom shows weak upwelling, a thicker nutrient-poor surface layer, and reduced plankton during El Nino. World map illustrating the generalized weather effects of El Nino from December through February. Regions are labeled and shaded to show conditions such as warm in parts of North America, Asia, and South America; wet in the southern United States and eastern South America; dry and warm in southern Africa and Southeast Asia; wet and cool in the northern United States; and wet and warm across central and eastern equatorial Pacific. Images of sea-surface height taken during the El Nino episodes of 1997 and 2015. Graph depicting the influence of El Niño/Southern Oscillation (ENSO) on rainfall produced by the Indian summer monsoon. During years when ENSO is active, monsoon-driven precipitation over India often declines.
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El Niño: References & Edit History

Article Contributors

Primary Contributors

  • David B. Enfield
    Research Oceanographer, Atlantic Oceanographic and Meteorological Laboratory, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, Miami.
  • The Editors of Encyclopaedia Britannica
    Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.

Other Contributors

  • J.E. Luebering
    J.E. Luebering is Senior Vice President and Acting Editor in Chief at Encyclopaedia Britannica.

Other Encyclopedia Britannica Contributors

Article History

Type Description Contributor Date
Corrected display issue. Aug 19, 2026
Added media. Aug 14, 2026
Added map. Jul 13, 2026
Add new Web site: Roger Williams University Open Publishing - Introduction to Oceanography - El Niño and La Niña. May 22, 2026
Removed video, added photograph, and added top questions. May 11, 2026
Translation of El Niño changed, and its multiple meanings explained. Jan 10, 2025
Add new Web site: Space.com - What are El Ni�o and La Ni�a and how do they affect Earth's weather? Apr 25, 2024
Add new Web site: NASA Climate Kids - El Ni�o quiets monster storms. May 13, 2019
Add new Web site: LiveScience - What Is El Ni�o? May 13, 2019
Text describing the 2015–16 El Niño episode added. Jun 06, 2016
Added video describing the El Niño and La Niña phenomena. Feb 09, 2011
New text changing the regularity of El Niño episodes from five to ten years to two to seven years added. Dec 31, 2009
New text describing the Oceanic Nino Index (ONI), the standard measure determining the presence of an El Nino episode, added. Text associated with the NINO3 index has been removed. Dec 31, 2009
New text describing the 1997-98 El Niño episode added. Aug 26, 2009
Media added. Feb 26, 2009
Media added. May 15, 2007
Added new Web site: Pacific Marine Environmental Laboratory - El Nino Theme Page. Oct 10, 2006
Added new Web site: PBS Online - Tracking El Nino. Sep 22, 2006
Added new Web site: PBS Online - Savage Seas. Aug 08, 2006
Added new Web site: PBS Online - Savage Seas. Aug 08, 2006
Added new Web site: National Geographic Society - El Ni�o. May 10, 2006
Added new Web site: National Geographic Society - El Ni�o. May 10, 2006
Article added to new online database. Jul 20, 1998
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