El Niño and La Niña are climate patterns that can affect global weather. During typical Pacific ocean conditions, trade winds blow west beside the equator. These winds bring with it South America’s warm water toward Asia. Then, cold water that rises from the depths in a process known as upwelling replaces the warm water.
The contrasting patterns of el Niño and La Niña disrupt these neutral conditions of the Pacific. Scientists call these events or cycles El Niño-Southern Oscillation (ENSO). These periodic weather phases can have noticeable impacts on global weather, ecosystems, wildfires, economies.
In this article, you can find all the relevant information about El Niño and La Niña. You can share it with your family members and friends to let them know all about it! Help them understand the weather and how these periodic changes can affect the global climate.
What Is El Niño?
El Niño is the warming phase of the ENSO cycle. During it, trade winds become weaker, and warm water moves east towards America’s west coast. The term means “the boy” in Spanish.
El Niño got its name from the South American fishermen who first noticed the Pacific ocean’s strangely warm waters back in the 1600s. The full name they gave to this phenomenon was El Niño de Navidad because the warmth usually peaks during the early winter.
It can significantly affect the weather in North America. The warm waters cause the jet stream in the Eastern Pacific to dip from its neutral position. This position change causes areas in Canada and the northern United States to become warmer and drier than usual. Conversely, it leads to a flooding increase and wetter periods in the southern United States and the Gulf Coast.
El Niño can considerably impact marine ecosystems that live off the Pacific Coast as well. Typical conditions in the Pacific Ocean bring nutrient-rich and cold water from the depths to the ocean’s surface. El Niño weakens this upwelling or effectively stops it.
This change upsets the marine food web by lowering the available nutrients. During this period, the number of phytoplankton on the coast reduces. Consequently, it affects the fish that feed upon them, and everything else that eats the fish, and so on. The change in the water temperature can bring tropical fish species such as albacore tuna into places that are typically too cold.
Meteorologists declare an El Niño when the tropical eastern Pacific’s sea temperature rises half a centigrade above the current long-term average. The people living along the tropical east Pacific can significantly feel this occurrence thanks to the resulting warmer climate.
What Is La Niña?
La Niña is the opposite effect of El Niño. It means “the girl” in Spanish, but it also goes by several other names such as anti-El Niño and El Viejo. Some scientists simply call it “a cold event.” This phenomenon enhances the Pacific’s neutral conditions.
The trade winds blow harsher than customary because the air pressure average is lower in Australia and higher in Tahiti. This change pushes the warm water toward Asia from America’s west coast. It increases upwelling and brings back the nutrient-rich and cold water to the ocean’s surface.
The cold water pushes the Pacific jet stream back north. Unfortunately, it may lead to droughts in the southern United States. Canada and the Pacific Northwest can see more instances of flooding and heavy rains.
During La Niña, temperatures are warmer than usual during winter in the south and colder than expected in the north. In some cases, a La Niña occurrence can end up causing a severe hurricane season.
This phenomenon also affects species living on the Pacific coast, although not as severely as El Niño. As the waters get colder, they become more nutrient-rich than usual. This environmental condition can support more marine life, resulting in the appearance of cold-water species on the coast of California. During a La Niña year, it isn’t strange to see squids and salmons there.
The conditions to declare a La Niña vary between meteorology agencies. Still, when this event happens, the Pacific ocean’s temperature can go between three and five centigrades below the current long-term average.
Between the El Niño and La Niña, the ENSO cycle has a neutral phase in which conditions are closer to the norm, with temperatures being within 0.5 centigrades. These conditions are typical after these cooling or warming periods. In fact, meteorologists describe nearly half of the ENSO cycle as neutral.
How Does It Occur and What Happens During It?
The ENSO phases are natural events that result from variations of the ocean’s temperature in the equatorial Pacific. It impacts the global climate, making changes in the atmosphere and affecting the ocean’s currents and temperatures.
The cycle states alter between El Niño (warm,) neutral (neither,) and La Niña (cold.) Both El Niño and La Niña phases break the Pacific ocean’s neutral balance. During an El Niño, the air pressure currents in the South Pacific reverse direction. This effect makes trade winds lose strength.
As a result, the water flow from America’s west coast to the Pacific decreases, and ocean water starts to accumulate, reducing upwelling and pushing the thermocline deeper. This thermocline and decreased water flow lead to sea surface temperatures higher than expected in the Eastern Pacific.
During a La Niña, the effect is the opposite. The west coast of America experiences increased upwelling and lower sea surface temperatures. It causes more rainfall in the Central Pacific, while the Western Pacific experiences warmer and drier climates.
How Often Does It Occur?
The frequency of El Niño and La Niña occurrences is irregular. They happen every two to seven years on average. Still, El Niño typically occurs more as its episodes are shorter.
How Long Does It Last?
El Niño and La Niña events usually last from 9 to 12 months. Still, La Niña can occasionally have episodes that last considerably longer (between two and three years) than El Niño, which rarely has instances where it lasts more than 12 months.
Both phases usually begin during spring and early summer (between March and June) and start to reach their peak intensity between late autumn and mid-winter (between November and February.) As a year passes and spring comes again, it usually ends as the current phase weakens.
Why Are El Niño and La Niña Important?
These ENSO cycles are significantly important as they can influence many aspects of human life and more. They can impact global climate, weather, and ocean conditions. The phases can also affect human health, water supplies, and food conditions on some occasions.
It’s crucial to make previsions, even more so for people that live near the Pacific coast as El Niño and La Niña phases affect the surrounding areas. The cycles can increase the number of severe weather events in specific regions. These events include floods, droughts, and storms.
Causes and Effects of El Niño and La Niña
El Niño and La Niña are naturally reoccurring phenomena that have happened for millennia. Some scientists suspect that they’re becoming more frequent and intense due to climate change. Still, the mechanism in which they interact with climate change and global warming isn’t entirely clear.
Some scientists believe that climate change has increased the frequency of severe weather events during El Niño and La Niña cycles. Regardless, further research is necessary to separate the variability of trending human activities and natural climate.
Although ENSO cycles influence global climate patterns, they neither impact every region nor affect every area in the same way. For example, parts of Indonesia and Australia suffer droughts during the El Niño cycle but experience more rainfall during La Niña. This contrasting behavior also occurs in several locations around the tropics.
People who want to get accurate information at a local level should approach their corresponding National Meteorological Agency. The World Meteorological Organization (WMO) may also provide information on how El Niño and La Niña could affect certain localities. The impacts of each ENSO cycle are never the same. It often depends on the time of year it develops, the intensity, and whether it interacts with other climate patterns.
For example, the El Niño event between 2015 and 2016 affected more than 60 million people. Relief organizations couldn’t determine the exact number of affected people. The areas that extreme weather events affected the most were Southern Africa, East Africa, South East Asia, Central America, and the Pacific Islands. These regions experienced frequent flooding and rains.
Some countries faced serious humanitarian fallouts, including rising prices, increased malnutrition rates, ravaged livelihoods, forced displacement, and increased malnutrition and food insecurity due to reduced crop yields.
There was also an outbreak of waterborne diseases such as typhoid and cholera due to excessive rainfall. Malaria and other vector-borne diseases also saw an increase. Over 23 countries issued humanitarian appeals, which in total added up to more than 5 billion USD.
On the other hand, the cold episodes of La Niña are associated with heavy rainfall in the Philippines, Thailand, Indonesia, and eastern Australia. This event also leads to heavy rain In Colombia, the northeast region of Brazil, and other northern areas of South America. In Uruguay and some parts of Argentina, the event resulted in a deficiency instead.
The climate is drier along the coast of Ecuador and the northern shores of Peru. Overall, the La Niña weather conditions are stormier and colder in the north and warmer and calmer in the south.
Can Scientists Predict El Niño and La Niña Episodes and How?
Scientists can predict the arrival of ENSO cycles several months or even a year in advance. It’s possible with the help of contemporary climate models and observation data, which includes information gathered from sensors on ocean buoys and satellites. These weather instruments regularly monitor the ocean and atmosphere’s changing conditions.
Scientists developed the first ENSO prediction model in the 1980s. Nowadays, numerous computer models worldwide employ atmospheric conditions and sea surface temperatures to diagnose the ENSO status a year or further in the future.
Forecasters examine the results of these multi-model ensembles to find where they agree. This method lets them determine whether it’s necessary to issue a new ENSO forecast. Some leading sources of prediction forecasts are the National Oceanic and Atmospheric Administration Climate Center (NOAA), the Australian Bureau of Meteorology, and the International Research Institute for Climate and Society (IRI), which works alongside NOAA.
A collaborative effort between the WMO, IRI, and contributions from other experts and institutions worldwide prepared an El Niño and La Niña update that provides an outlook every three months approximately. Other institutions like the Climate Prediction Center also work alongside IRI to provide a consensus forecast every first half of each month.
These forecasts predict stronger El Niño and La Niña cycles more accurately than minor ones. For example, a 2012 study in the Bulletin of the American Meteorological Society found out that the skills of 20 prediction models between 2002 and 2011 were lower than those of older models between the 1980s and 1990s.
However, the reason for the decline was that the recent ENSO events were considerably more variable, making it harder for the models to output an accurate forecast. The prediction models themselves were better than older ones.
Why Are They Called El Niño and La Niña?
El Niño directly translates from Spanish to “the boy.” It’s a simplistic form of the previous term that Peruvian fishermen used: El Niño de Navidad after the newborn Christ. They named the phenomenon that way because the waters were often the warmest around Christmas.
After some time, it became the accepted term to describe the phenomenon that disrupts the Pacific ocean’s neutral conditions. La Niña, which is the opposite of El Niño, means “the girl.”
El Niño and La Niña are stages of the El Niño Southern Oscillation. They cause changes in global temperatures and rainfall events in the areas they affect. El Niño is the warm phase of the two, where the sea surface temperature of the Pacific ocean rises. La Niña causes the opposite effect, dropping the temperature.
Each stage lasts up to a year, with La Niña lasting more than a year on several occasions. El Niño also had some long-term instances, but they’re considerably rare.
Help your friends understand the origins, causes, and effects of El Niño and La Niña with this guide! Here you can find every helpful fact about these occurrences.