The information here should answer most of your questions about El Niño. If it doesn't, don't hesitate to send us your question, using the Ask Jack a question form. Be sure to tell us you've consulted this page and what kind of detail you need that wasn't here.
Q: What is an El Niño?
A: El Niño originally was the name used for warmer than normal sea surface temperatures in the Pacific Ocean off the west coast of South America. It occurs when the easterly winds die down, in turn allowing for warmer waters normally kept in the western Pacific to drift eastward towards the Americas. El Niño is Spanish for 'the Christ child' and gets this name because it is known to occur during the Christmas season off the coast of South America. Now, El Niño has come to refer to a whole complex of Pacific Ocean sea-surface temperature changes and global weather events. The warming off South America is just one of these events. Our El Niño page has links to more information.
Q: What is ENSO?
A: It is the "El Niño-Southern Oscillation," the name scientists use for what is often called El Niño. Historically, El Niño referred to warming of ocean water in the eastern Pacific. The Southern Oscillation is a see-saw shift in surface air pressure between Darwin, Australia, and Tahiti. When pressure is high at Darwin, it's low at Tahiti and vice versa. In the 1950s scientists realized that the El Niño and the Southern Oscillation were parts of the same event. During normal times, the pressure is lower at Darwin than at Tahiti. But during the warm phase, usually called "El Niño," the pressure is lower at Tahiti.
Q: What is the difference between El Niño and La Niña?
A: Both refer to different phases of ENSO. El Niño refers to a pattern characterized by the tropical Pacific's warmest water spreading eastward to the coast of South America. La Niña refers to times when waters of the tropical Pacific are colder than normal.
Q: How can I find out what the likely effects of El Niño and La Niña on other parts of North America?
A: USA TODAY has recently posted an FAQ covering the effects El Niño will have on Mexico, the Caribbean, Bahamas, central America and parts of northern South America. It has details about how El Niño might disrupt your vacation plans.
Florida State University's Center For Ocean-Atmospheric Prediction Studies has maps showing the general effects during the four seasons of both phases of ENSO. Click here to go to these maps.
Click here to go to our index to long-term forecasts from the National Weather Service. These are for three-month "seasons" for a year ahead.
The National Oceanic and Atmospheric Administration has links to more detailed information about the effects of El Niño. Click here to go to the list.
Q: Does El Niño effect Australia more than other areas of the world?
A: El Niño can be a major influence on Australia's weather. For example, it's often linked to droughts there. Northern Australia is in the tropics, which are affected more than mid-latitude regions. Also, the normally warm part of the Pacific is close to Australia and this warm water helps encourage thunderstorms. Dying the warm phase of an El Niño some of this warm water moves eastward, reducing the amount of rain for a large area of the western Pacific, including parts of Australia.
Q: How does El Niño affect sea life and birds?
A: El Niño cuts off the upwelling of cold water from lower-levels of the ocean off the Pacific Coast of South America. This upwelling, colder water brings many of the nutrients that keep the food chain going. When this happens, the fish either die or migrate north or south into areas where they'll find more to eat. With the fish gone, the sea birds that depend on them either die or go elsewhere.
While the effects are most striking off the South American Coast, other areas are also affected. The following links have more information about El Niño's effects on marine life.