What is El Nino and La Nina

Often times, major climatic events such as El Niño and La Niña are mentioned during discussions pertaining to global warming. While their existence is not necessarily a sign of worsening climate conditions, their frequency and severity is.

Niño and La Niña are two stages of the Southern Oscillation. In essence, this means they represent two different stages of a turbulent, cyclical pattern that routinely occurs. Fisherman on the Pacific Coast of South America first took note of these phenomena as far back as the 16th century, however they were not documented scientifically until the 1920s, at which time scientists observed periodic climatic occurrences every three to seven years there in the eastern Pacific. However, the intensity as well as the frequency of both El Niño and La Niña has increased significantly since the 1970s. This is believed to be thanks primarily to global warming.

The El Niño portion of the cycle is expected to bring warmer sea temperatures, greater precipitation (in the northern hemisphere) and lower atmospheric pressure, according to the National Oceanic and Atmospheric Administration (NOAA). On the most extreme occasions, the results of El Niño have included such disasters as flooding from Ecuador to the Gulf of Mexico, vast amounts of marine life casualties in the Pacific, droughts in several parts of the world from Southern India to Australia and even Central America, to devastating hurricanes in Tahiti and Hawaii.

La Niña, on the other hand, usually brings cooler sea temperatures and higher atmospheric pressure, along with generally drier air. During this phase of the Southern Oscillation, oceanic currents cause nutrients from deep water to be brought up, providing an abundance of food for marine organisms (in sharp contrast to the marine life that is extinguished by the El Niño portion). In addition, La Niña usually brings strong accompanying winds that blow moisture away, making for very clear skies as well as very dry conditions in countries near the equator ranging from the International Date Line east to South America.

So what’s the relation between El Niño, La Niña and global warming? Well, many scientists subscribe to the belief that the increased severity and frequency of the two events in recent years is due to the warmer ocean temperatures caused by global warming. Scientists from NOAA reported in 1998 that higher global temperatures could possibly be encouraging more rapid evaporation from land, which is adding moisture to the air and subsequently intensifying the climatic activity usually associated with El Niño.

Kevin Trenberth, a climatologist at the National Center for Atmospheric Research in Colorado has his own take on the issue. He believes that the Southern Oscillation could possibly be functioning as sort of a pressure release valve for the tropics. With the rising temperatures caused by global warming, weather systems and ocean currents may not be capable of releasing all of the extra heat that gets pumped into tropical areas. In that case, El Niño serves a function that is required more often as our greenhouse gas emissions increase.

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.