Climate cycles

  • Exhibition Text

    • The seasons, which are caused by the tilt of the Earth’s axis, are the most important periodic fluctuations in climate. But changes in atmospheric and oceanic circulation pat-terns also cause periodic changes in climate on a global scale. The best known is El Niño– Southern Oscillation (ENSO), which originates in the Pacific Ocean but creates effects around the world. Less well known is the North Atlantic Oscillation, which affects the climates of northern Europe and the Maritime Provinces in Canada.

      El Nino
      Every two to seven years, the El Niño phenomenon causes atmospheric pressure over the western Pacific Ocean to rise. The equatorial ocean currents that usually flow westward reverse themselves, and the normally cold waters off the coasts of Peru and Chile are replaced with warmer water. This prevents cold, nutrient-rich water from welling up, ruining coastal fishing. It typically happens around Christmastime, hence the name El Niño, or the Christ child. 

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  • For Educators

    • Topic: Earth Science

      Subtopic: Climate/Climate Change

      Keywords: Climatology, Ocean temperature, Ocean circulation, Ocean-atmosphere interaction, Weather, El Nino Current, Droughts, Rain and rainfall

      Audience: General

In This Section

The record of El Nino

The record of El Nino

El Niño–Southern Oscillation (ENSO) is a phenomenon of the atmosphere and ocean that is observed in many different climate records.

Coral core

Coral core

These are sections cut from a core of coral (Porites lobata) that grew between 1937 and 1994.