What are “El Niño” and “La Niña” and what relationship do they have with global climate change?
What are “El Niño” and “La Niña” and what relationship do they have with global climate change?
—Ralph Carpio, Delray Beach, FL
Simply put, El Niño and La Niña are different stages in a cyclical pattern of climate turbulence otherwise known by meteorologists as the Southern Oscillation. First noticed by 16th century fishermen on the Pacific coast of South America, these phenomena were not scientifically documented until the 1920s when scientists noticed periodic occurrences every three to seven years in the eastern Pacific. Since the 1970s, though, El Niño and La Niña have been occurring with more frequency and intensity.
According to the National Oceanic and Atmospheric Administration (NOAA), the El Niño part of the cycle involves warmer-than-usual sea temperatures, great amounts of rainfall (in the northern hemisphere) and low atmospheric pressure. The most extreme results of an El Niño event have included flooding from Ecuador to the Gulf of Mexico, massive marine life die-offs in the Pacific, hurricanes in Tahiti and Hawaii, and concurrent droughts in many other parts of the world from Southern India to Australia to Central America.
In contrast, cooler sea temperatures, high atmospheric pressure and drier air characterize the La Niña phase of the Southern Oscillation. During La Niña, currents bring nutrients up from the deep water, providing feast, rather than famine, for marine organisms. And accompanying strong winds blow moisture away, making for cloudless skies and dry conditions in equatorial countries from the International Date Line east to South America.
Some scientists believe that the increased intensity and frequency—now every two to three years—of El Niño and La Niña events in recent decades is due to warmer ocean temperatures resulting from global warming. In a 1998 report, scientists from NOAA explained that higher global temperatures might be increasing evaporation from land and adding moisture to the air, thus intensifying the storms and floods associated with El Niño.
Another take on what’s happening is from Kevin Trenberth, a climatologist at the Colorado-based National Center for Atmospheric Research. Trenberth believes that the Southern Oscillation may be functioning like a pressure release valve for the tropics. With global warming driving temperatures higher, ocean currents and weather systems might not be able to release all the extra heat getting pumped into the tropical seas; as such an El Niño occurs to help expel the excess heat.
CONTACTS