The currents that power the ocean fluctuate from year to year, and these variations influence the atmosphere. One of the most famous and powerful of these ocean-atmosphere interactions is El Niño, the unusually warm current that invades South and Central American coastal waters at the end of some years. This unexpected warm water causes changes in fish populations, rainfall and weather across North and South America.

In a normal year, steady winds blow westward and push warm surface water toward the western Pacific Ocean. In contrast, during an El Niño year, weakened winds allow warm water to occupy the entire tropical Pacific. Rain follows the warm water eastward, causing drought in Indonesia and Australia and altering the path of the Jet Stream, which helps determine the weather in North America.

Although scientists don't fully understand how fluctuations such as El Niño work, they are learning more about them. Early prediction for such events will help people be better prepared to deal with the next El Niño and save lives and property.