El Niño


The name "El Niño" has become familiar to many people as the cause of unpleasant, even extreme, weather. To Californians, it means heavy rains, floods, and mudslides. To Australians, it brings thoughts of drought and catastrophic wildfires. But to meteorologists and oceanographers, El Niño is a fascinating glimpse into the intricate dance of the ocean and the atmosphere and the swirling patterns of heat and moisture that describe the global climate.

Peruvian fishermen have long noted that in some winters, coastal waters heat up and fish stocks dwindle, a phenomenon they named El Niño, (a reference to the birth of the Christ child, which also came in winter). Scientifically, El Niño refers to unusual sea surface temperatures throughout the equatorial Pacific, and to the resulting worldwide weather effects. An El Niño condition is officially declared by NOAA (the National Oceanographic and Atmospheric Administration) when a 3-month average of sea surface temperatures in the east central equatorial Pacific Ocean is 0.5° C or more above normal. Historically, El Niño occurred about once or twice per decade, but there is some indication that their frequency is increasing.

Severe El Niños cause death and destruction across countries, even continents, and yet the cause and consequences of these events is still not well understood. Only recently has the technology been available to allow scientists to study, model, and begin to predict global weather and climate.


In this activity, you will explore the links between ocean currents, El Niño, and weather. Examine the images and graphics below, and then answer the questions that follow.