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El Niño–Southern Oscillation (ENSO) is a global climate phenomenon that emerges from variation in winds and sea surface temperatures over the tropical Pacific Ocean. Those variations have an irregular pattern but do have some semblance of cycles. The occurrence of ENSO is not predictable. It affects the climate of much of the tropics and subtropics, and has links (teleconnections) to higher-latitude regions of the world. The warming phase of the sea surface temperature is known as "El Niño" and the cooling phase as "La Niña". The Southern Oscillation is the accompanying atmospheric oscillation, which is coupled with the sea temperature change.
El Niño is associated with higher than normal air sea level pressure over Indonesia, Australia and across the Indian Ocean to the Atlantic. La Niña has roughly the reverse pattern: high pressure over the central and eastern Pacific and lower pressure through much of the rest of the tropics and subtropics.<ref name="CPC ENSO">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Climate Change 2007">Template:Cite book</ref> The two phenomena last a year or so each and typically occur every two to seven years with varying intensity, with neutral periods of lower intensity interspersed.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> El Niño events can be more intense but La Niña events may repeat and last longer.
A key mechanism of ENSO is the Bjerknes feedback (named after Jacob Bjerknes in 1969) in which the atmospheric changes alter the sea temperatures that in turn alter the atmospheric winds in a positive feedback. Weaker easterly trade winds result in a surge of warm surface waters to the east and reduced ocean upwelling on the equator. In turn, this leads to warmer sea surface temperatures (called El Niño), a weaker Walker circulation (an east-west overturning circulation in the atmosphere) and even weaker trade winds. Ultimately the warm waters in the western tropical Pacific are depleted enough so that conditions return to normal. The exact mechanisms that cause the oscillation are unclear and are being studied.
Each country that monitors the ENSO has a different threshold for what constitutes an El Niño or La Niña event, which is tailored to their specific interests.<ref name="December 2014 EU2" /> El Niño and La Niña affect the global climate and disrupt normal weather patterns, which as a result can lead to intense storms in some places and droughts in others.<ref name="NIWA El Niño/La Niña" /><ref name="How Much Do El Niño" /> El Niño events cause short-term (approximately 1 year in length) spikes in global average surface temperature while La Niña events cause short term surface cooling.<ref name=":1" /> Therefore, the relative frequency of El Niño compared to La Niña events can affect global temperature trends on timescales of around ten years.<ref name=":2" /> The countries most affected by ENSO are developing countries that are bordering the Pacific Ocean and are dependent on agriculture and fishing.
In climate change science, ENSO is known as one of the internal climate variability phenomena.<ref name="IPCC2021">IPCC, 2021: Climate Change 2021: The Physical Science Basis Template:Webarchive. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change Template:Webarchive [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2391 pp. doi:10.1017/9781009157896.</ref>Template:Rp Future trends in ENSO due to climate change are uncertain,<ref name="Collins10">Template:Cite journal</ref> although climate change exacerbates the effects of droughts and floods. The IPCC Sixth Assessment Report summarized the scientific knowledge in 2021 for the future of ENSO as follows: "In the long term, it is very likely that the precipitation variance related to El Niño–Southern Oscillation will increase".<ref name="IPCC2021" />Template:Rp The scientific consensus is also that "it is very likely that rainfall variability related to changes in the strength and spatial extent of ENSO teleconnections will lead to significant changes at regional scale".<ref name="IPCC2021" />Template:Rp
Definition and terminologyEdit
The El Niño–Southern Oscillation is a single climate phenomenon that periodically fluctuates between three phases: Neutral, La Niña or El Niño.<ref name="ENSO:Nutshell">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> La Niña and El Niño are opposite phases in the oscillation which are deemed to occur when specific ocean and atmospheric conditions are reached or exceeded.<ref name="ENSO:Nutshell" />
An early recorded mention of the term "El Niño" ("The Boy" in Spanish) to refer to climate occurred in 1892, when Captain Camilo Carrillo told the geographical society congress in Lima that Peruvian sailors named the warm south-flowing current "El Niño" because it was most noticeable around Christmas.<ref>Carrillo, Camilo N. (1892) "Disertación sobre las corrientes oceánicas y estudios de la correinte Peruana ó de Humboldt" Template:Webarchive (Dissertation on the ocean currents and studies of the Peruvian, or Humboldt's, current), Boletín de la Sociedad Geográfica de Lima, 2 : 72–110. [in Spanish] From p. 84: "Los marinos paiteños que navegan frecuentemente cerca de la costa y en embarcaciones pequeñas, ya al norte ó al sur de Paita, conocen esta corriente y la denomination Corriente del Niño, sin duda porque ella se hace mas visible y palpable después de la Pascua de Navidad." (The sailors [from the city of] Paita who sail often near the coast and in small boats, to the north or the south of Paita, know this current and call it "the current of the Boy [el Niño]", undoubtedly because it becomes more visible and palpable after the Christmas season.)</ref> Although pre-Columbian societies were certainly aware of the phenomenon, the indigenous names for it have been lost to history.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The capitalized term El Niño refers to the Christ Child, Jesus, because periodic warming in the Pacific near South America is usually noticed around Christmas.<ref name="DFG">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Originally, the term El Niño applied to an annual weak warm ocean current that ran southwards along the coast of Peru and Ecuador at about Christmas time.<ref name="Definition">Template:Cite journal</ref> However, over time the term has evolved and now refers to the warm and negative phase of the El Niño–Southern Oscillation (ENSO). The original phrase, El Niño de Navidad, arose centuries ago, when Peruvian fishermen named the weather phenomenon after the newborn Christ.<ref>Template:Cite news</ref><ref>Template:Cite news</ref>
La Niña ("The Girl" in Spanish) is the colder counterpart of El Niño, as part of the broader ENSO climate pattern. In the past, it was also called an anti-El Niño<ref name="USNOAA-NOS-NinoNina">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and El Viejo, meaning "the old man."<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
A negative phase exists when atmospheric pressure over Indonesia and the west Pacific is abnormally high and pressure over the east Pacific is abnormally low, during El Niño episodes, and a positive phase is when the opposite occurs during La Niña episodes, and pressure over Indonesia is low and over the west Pacific is high.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
FundamentalsEdit
On average, the temperature of the ocean surface in the tropical East Pacific is roughly Template:Cvt cooler than in the tropical West Pacific. The sea surface temperature (SST) of the West Pacific northeast of Australia averages around Template:Cvt. SSTs in the East Pacific off the western coast of South America are closer to Template:Cvt. Strong trade winds near the equator push water away from the East Pacific and towards the West Pacific.<ref name="BOM About ENSO" /> This water is slowly warmed by the Sun as it moves west along the equator.<ref name="ENSO and Australia" /> The ocean surface near Indonesia is typically around Template:Cvt higher than near Peru because of the buildup of water in the West Pacific.<ref name="Effects ENSO Pacific" />Template:Clarify The thermocline, or the transitional zone between the warmer waters near the ocean surface and the cooler waters of the deep ocean,<ref name="What ENSO IRI">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is pushed downwards in the West Pacific due to this water accumulation.<ref name="Effects ENSO Pacific" />
The total weight of a column of ocean water is almost the same in the western and east Pacific. Because the warmer waters of the upper ocean are slightly less dense than the cooler deep ocean, the thicker layer of warmer water in the western Pacific means the thermocline there must be deeper. The difference in weight must be enough to drive any deep water return flow.<ref name="Sarachik and Cane 2010">Template:Cite book</ref>Template:Rp Consequently, the thermocline is tilted across the tropical Pacific, rising from an average depth of about Template:Cvt in the West Pacific to a depth of about Template:Cvt in the East Pacific.<ref name="Effects ENSO Pacific">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Cooler deep ocean water takes the place of the outgoing surface waters in the East Pacific, rising to the ocean surface in a process called upwelling.<ref name="BOM About ENSO" /><ref name="ENSO and Australia" /> Along the western coast of South America, water near the ocean surface is pushed westward due to the combination of the trade winds and the Coriolis effect. This process is known as Ekman transport. Colder water from deeper in the ocean rises along the continental margin to replace the near-surface water.<ref name="OceanMotion">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This process cools the East Pacific because the thermocline is closer to the ocean surface, leaving relatively little separation between the deeper cold water and the ocean surface.<ref name="Effects ENSO Pacific" /> Additionally, the northward-flowing Humboldt Current carries colder water from the Southern Ocean to the tropics in the East Pacific.<ref name="BOM About ENSO" /> The combination of the Humboldt Current and upwelling maintains an area of cooler ocean waters off the coast of Peru.<ref name="BOM About ENSO" /><ref name="ENSO and Australia" /> The West Pacific lacks a cold ocean current and has less upwelling as the trade winds are usually weaker than in the East Pacific, allowing the West Pacific to reach warmer temperatures. These warmer waters provide energy for the upward movement of air. As a result, the warm West Pacific has on average more cloudiness and rainfall than the cool East Pacific.<ref name="BOM About ENSO">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
ENSO describes a quasi-periodic change of both oceanic and atmospheric conditions over the tropical Pacific Ocean.<ref name="BOM About ENSO" /> These changes affect weather patterns across much of the Earth.<ref name="ENSO and Australia">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The tropical Pacific is said to be in one of three states of ENSO (also called "phases") depending on the atmospheric and oceanic conditions.<ref name="ENSO Nutshell">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> When the tropical Pacific roughly reflects the average conditions, the state of ENSO is said to be in the neutral phase. However, the tropical Pacific experiences occasional shifts away from these average conditions. If trade winds are weaker than average, the effect of upwelling in the East Pacific and the flow of warmer ocean surface waters towards the West Pacific lessen. This results in a cooler West Pacific and a warmer East Pacific, leading to a shift of cloudiness and rainfall towards the East Pacific. This situation is called El Niño. The opposite occurs if trade winds are stronger than average, leading to a warmer West Pacific and a cooler East Pacific. This situation is called La Niña and is associated with increased cloudiness and rainfall over the West Pacific.<ref name="BOM About ENSO" />
Bjerknes feedbackEdit
The close relationship between ocean temperatures and the strength of the trade winds was first identified by Jacob Bjerknes in 1969. Bjerknes also hypothesized that ENSO was a positive feedback system where the associated changes in one component of the climate system (the ocean or atmosphere) tend to reinforce changes in the other.<ref name="Wang et al. 2017">Template:Cite book</ref>Template:Rp For example, during El Niño, the reduced contrast in ocean temperatures across the Pacific results in weaker trade winds, further reinforcing the El Niño state. This process is known as Bjerknes feedback.<ref name="Rise El Nino">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Although these associated changes in the ocean and atmosphere often occur together, the state of the atmosphere may resemble a different ENSO phase than the state of the ocean or vice versa.<ref name="ENSO Nutshell" /> Because their states are closely linked, the variations of ENSO may arise from changes in both the ocean and atmosphere and not necessarily from an initial change of exclusively one or the other.<ref name="What El Nino Scripps">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Rise El Nino" /> Conceptual models explaining how ENSO operates generally accept the Bjerknes feedback hypothesis. However, ENSO would perpetually remain in one phase if Bjerknes feedback were the only process occurring.<ref name="Wang et al. 2017" />Template:Rp Several theories have been proposed to explain how ENSO can change from one state to the next, despite the positive feedback.<ref name="Wang 2018">Template:Cite journal</ref> These explanations broadly fall under two categories.<ref name="Yang et al. 2018">Template:Cite journal</ref> In one view, the Bjerknes feedback naturally triggers negative feedbacksTemplate:Clarify that end and reverse the abnormal state of the tropical Pacific. This perspective implies that the processes that lead to El Niño and La Niña also eventually bring about their end, making ENSO a self-sustainingTemplate:Clarify process.<ref name="Wang et al. 2017" />Template:Rp Other theories view the state of ENSO as being changed by irregular and external phenomena such as the Madden–Julian oscillation, tropical instability waves, and westerly wind bursts.<ref name="Wang et al. 2017" />Template:Rp
Walker circulationEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} The three phases of ENSO relate to the Walker circulation, which was named after Gilbert Walker who discovered the Southern Oscillation during the early twentieth century. The Walker circulation is an east-west overturning circulation in the vicinity of the equator in the Pacific. Upward air is associated with high sea temperatures, convection and rainfall, while the downward branch occurs over cooler sea surface temperatures in the east. During El Niño, as the sea surface temperatures change so does the Walker Circulation. Warming in the eastern tropical Pacific weakens or reverses the downward branch, while cooler conditions in the west lead to less rain and downward air, so the Walker Circulation first weakens and may reverse.<ref>Template:Cite book</ref>Template:Rp]
Southern OscillationEdit
The Southern Oscillation is the atmospheric component of ENSO. This component is an oscillation in surface air pressure between the tropical eastern and the western Pacific Ocean waters. The strength of the Southern Oscillation is measured by the Southern Oscillation Index (SOI). The SOI is computed from fluctuations in the surface air pressure difference between Tahiti (in the Pacific) and Darwin, Australia (on the Indian Ocean).<ref name="Aus">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
El Niño episodes have negative SOI, meaning there is lower pressure over Tahiti and higher pressure in Darwin. La Niña episodes on the other hand have positive SOI, meaning there is higher pressure in Tahiti and lower in Darwin.
Low atmospheric pressure tends to occur over warm water and high pressure occurs over cold water, in part because of deep convection over the warm water. El Niño episodes are defined as sustained warming of the central and eastern tropical Pacific Ocean, thus resulting in a decrease in the strength of the Pacific trade winds, and a reduction in rainfall over eastern and northern Australia. La Niña episodes are defined as sustained cooling of the central and eastern tropical Pacific Ocean, thus resulting in an increase in the strength of the Pacific trade winds, and the opposite effects in Australia when compared to El Niño.
Although the Southern Oscillation Index has a long station record going back to the 1800s, its reliability is limited due to the latitudes of both Darwin and Tahiti being well south of the Equator, so that the surface air pressure at both locations is less directly related to ENSO.<ref name="EQSOI">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> To overcome this effect, a new index was created, named the Equatorial Southern Oscillation Index (EQSOI).<ref name="EQSOI" /><ref name="Indexes">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> To generate this index, two new regions, centered on the Equator, were defined. The western region is located over Indonesia and the eastern one over the equatorial Pacific, close to the South American coast.<ref name="EQSOI" /> However, data on EQSOI goes back only to 1949.<ref name="EQSOI" />
Sea surface height (SSH) changes up or down by several centimeters in Pacific equatorial region with the ESNO: El Niño causes a positive SSH anomaly (raised sea level) because of thermal expansion while La Niña causes a negative SSH anomaly (lowered sea level) via contraction.<ref>https://eospso.nasa.gov/sites/default/files/publications/ElNino-LaNina_508.pdf Template:Bare URL PDF</ref>
Three phases of sea surface temperatureEdit
The El Niño–Southern Oscillation is a single climate phenomenon that quasi-periodically fluctuates between three phases: Neutral, La Niña or El Niño.<ref name="ENSO:Nutshell" /> La Niña and El Niño are opposite phases which require certain changes to take place in both the ocean and the atmosphere before an event is declared.<ref name="ENSO:Nutshell" /> The cool phase of ENSO is La Niña, with SST in the eastern Pacific below average, and air pressure high in the eastern Pacific and low in the western Pacific. The ENSO cycle, including both El Niño and La Niña, causes global changes in temperature and rainfall.<ref name="CPC ENSO2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite book</ref>
Neutral phaseEdit
If the temperature variation from climatology is within 0.5 °C (0.9 °F), ENSO conditions are described as neutral. Neutral conditions are the transition between warm and cold phases of ENSO. Sea surface temperatures (by definition), tropical precipitation, and wind patterns are near average conditions during this phase.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Close to half of all years are within neutral periods.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> During the neutral ENSO phase, other climate anomalies/patterns such as the sign of the North Atlantic Oscillation or the Pacific–North American teleconnection pattern exert more influence.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
El Niño phaseEdit
El Niño conditions are established when the Walker circulation weakens or reverses and the Hadley circulation strengthens,Template:CnTemplate:Clarify leading to the development of a band of warm ocean water in the central and east-central equatorial Pacific (approximately between the International Date Line and 120°W), including the area off the west coast of South America,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="ENSO:Nutshell" /> as upwelling of cold water occurs less or not at all offshore.<ref name="Climate Change 2007" />
This warming causes a shift in the atmospheric circulation, leading to higher air pressure in the western Pacific and lower in the eastern Pacific,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> with rainfall reducing over Indonesia, India and northern Australia, while rainfall and tropical cyclone formation increases over the tropical Pacific Ocean.<ref name="What is an El Niño?3">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The low-level surface trade winds, which normally blow from east to west along the equator, either weaken or start blowing from the other direction.<ref name="ENSO:Nutshell" />
El Niño phases are known to happen at irregular intervals of two to seven years, and lasts nine months to two years.<ref name="autogenerated2005">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The average period length is five years. When this warming occurs for seven to nine months, it is classified as El Niño "conditions"; when its duration is longer, it is classified as an El Niño "episode".<ref name="administration1">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
ImageSize = width:800 height:70 PlotArea = left:50 bottom:20 width:700 height:40 Period = from:1900 till:2025 DateFormat = yyyy TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:5 start:1900 PlotData =
bar:elniño width:30 color:red mark:(line,white) from:1902 till:1903 from:1905 till:1906 from:1911 till:1912 from:1913 till:1915 from:1919 till:1920 from:1925 till:1926 from:1940 till:1942 from:1946 till:1947 from:1951 till:1952 from:1953 till:1954 from:1957 till:1958 from:1958 till:1959 from:1963 till:1964 from:1965 till:1966 from:1968 till:1969 from:1969 till:1970 from:1972 till:1973 from:1976 till:1977 from:1977 till:1978 from:1979 till:1980 from:1982 till:1983 from:1986 till:1988 from:1991 till:1992 from:1993 till:1994 from:1994 till:1995 from:1997 till:1998 from:2002 till:2003 from:2004 till:2005 from:2006 till:2007 from:2009 till:2010 from:2014 till:2016 from:2018 till:2019 from:2023 till:2024</timeline>
{{safesubst:#invoke:Check for unknown parameters|check|unknown=|preview=Page using Template:Center with unknown parameter "_VALUE_"|ignoreblank=y| 1 | style }}It is thought that there have been at least 30 El Niño events between 1900 and 2024, with the 1982–83, 1997–98 and 2014–16 events among the strongest on record.<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref> Since 2000, El Niño events have been observed in 2002–03, 2004–05, 2006–07, 2009–10, 2014–16, 2018–19,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and 2023–24.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Major ENSO events were recorded in the years 1790–93, 1828, 1876–78, 1891, 1925–26, 1972–73, 1982–83, 1997–98, 2014–16, and 2023–24.<ref name="Davis20012">Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite news</ref> During strong El Niño episodes, a secondary peak in sea surface temperature across the far eastern equatorial Pacific Ocean sometimes follows the initial peak.<ref>Template:Cite journal</ref>
La Niña phaseEdit
An especially strong Walker circulation causes La Niña, which is considered to be the cold oceanic and positive atmospheric phase of the broader El Niño–Southern Oscillation (ENSO) weather phenomenon, as well as the opposite of Template:Nowrap weather pattern,<ref name="USNOAA-NOS-NinoNina" /> where sea surface temperature across the eastern equatorial part of the central Pacific Ocean will be lower than normal by 3–5 °C (5.4–9 °F). The phenomenon occurs as strong winds blow warm water at the ocean's surface away from South America, across the Pacific Ocean towards Indonesia.<ref name="USNOAA-NOS-NinoNina" /> As this warm water moves west, cold water from the deep sea rises to the surface near South America.<ref name="USNOAA-NOS-NinoNina" />
The movement of so much heat across a quarter of the planet, and particularly in the form of temperature at the ocean surface, can have a significant effect on weather across the entire planet. Tropical instability waves visible on sea surface temperature maps, showing a tongue of colder water, are often present during neutral or La Niña conditions.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
La Niña is a complex weather pattern that occurs every few years,<ref name="USNOAA-NOS-NinoNina" /> often persisting for longer than five months. El Niño and La Niña can be indicators of weather changes across the globe. Atlantic and Pacific hurricanes can have different characteristics due to lower or higher wind shear and cooler or warmer sea surface temperatures.
ImageSize = width:800 height:70 PlotArea = left:50 bottom:20 width:700 height:40 Period = from:1900 till:2025 DateFormat = yyyy TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:5 start:1900 PlotData =
bar:laniña width:30 color:blue mark:(line,white) from:1903 till:1904 from:1906 till:1907 from:1909 till:1911 from:1916 till:1918 from:1924 till:1925 from:1928 till:1930 from:1938 till:1939 from:1942 till:1943 from:1949 till:1951 from:1954 till:1957 from:1964 till:1965 from:1967 till:1968 from:1970 till:1972 from:1973 till:1974 from:1974 till:1976 from:1983 till:1984 from:1984 till:1985 from:1988 till:1989 from:1995 till:1996 from:1998 till:2001 from:2005 till:2006 from:2007 till:2008 from:2008 till:2009 from:2010 till:2012 from:2016 till:2017 from:2017 till:2018 from:2020 till:2023
</timeline>A timeline of all La Niña episodes between 1900 and 2023.<ref name="Cold & Warm Episodes">Template:Cite report</ref><ref>Template:Cite report</ref> Note that each forecast agency has a different criteria for what constitutes a La Niña event, which is tailored to their specific interests.
La Niña events have been observed for hundreds of years, and occurred on a regular basis during the early parts of both the 17th and 19th centuries.<ref>Template:Cite journal</ref> Since the start of the 20th century, La Niña events have occurred during the following years:Template:Refn Template:Plainlist Template:Columns-list Template:Endplainlist
Transitional phasesEdit
Transitional phases at the onset or departure of El Niño or La Niña can also be important factors on global weather by affecting teleconnections. Significant episodes, known as Trans-Niño, are measured by the Trans-Niño index (TNI).<ref name="TNI">Template:Cite journal</ref> Examples of affected short-time climate in North America include precipitation in the Northwest US<ref>Template:Cite journal</ref> and intense tornado activity in the contiguous US.<ref>Template:Cite journal</ref>
VariationsEdit
ENSO ModokiEdit
The first ENSO pattern to be recognised, called Eastern Pacific (EP) ENSO, to distinguish it from others,<ref name="Yu2009">Template:Cite journal</ref> involves temperature anomalies in the eastern Pacific. However, in the 1990s and 2000s, variations of ENSO conditions were observed, in which the usual place of the temperature anomaly (Niño 1 and 2) is not affected, but an anomaly also arises in the central Pacific (Niño 3.4).<ref name="Larkin2007">Template:Cite journal</ref> The phenomenon is called Central Pacific (CP) ENSO,<ref name="Yu2009" /> "dateline" ENSO (because the anomaly arises near the dateline), or ENSO "Modoki" (Modoki is Japanese for "similar, but different").<ref name="link.springer.com">Template:Cite journal</ref><ref name="auto">Template:Cite journal</ref> There are variations of ENSO additional to the EP and CP types, and some scientists argue that ENSO exists as a continuum, often with hybrid types.<ref>Template:Cite journal</ref>
The effects of the CP ENSO are different from those of the EP ENSO. The El Niño Modoki is associated with more hurricanes more frequently making landfall in the Atlantic.<ref name="Kim2009">Template:Cite journal</ref> La Niña Modoki leads to a rainfall increase over northwestern Australia and northern Murray–Darling basin, rather than over the eastern portion of the country as in a conventional EP La Niña.<ref name="LNModoki">Template:Cite journal</ref> Also, La Niña Modoki increases the frequency of cyclonic storms over Bay of Bengal, but decreases the occurrence of severe storms in the Indian Ocean overall.<ref name="LNM Indian">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The first recorded El Niño that originated in the central Pacific and moved toward the east was in 1986.<ref>Template:Cite book</ref> Recent Central Pacific El Niños happened in 1986–87, 1991–92, 1994–95, 2002–03, 2004–05 and 2009–10.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Furthermore, there were "Modoki" events in 1957–59,<ref>Template:Cite journal</ref> 1963–64, 1965–66, 1968–70, 1977–78 and 1979–80.<ref>Template:Cite report</ref><ref>Template:Cite report.</ref> Some sources say that the El Niños of 2006-07 and 2014-16 were also Central Pacific El Niños.<ref>Template:Cite report</ref><ref>Template:Cite news</ref> Recent years when La Niña Modoki events occurred include 1973–1974, 1975–1976, 1983–1984, 1988–1989, 1998–1999, 2000–2001, 2008–2009, 2010–2011, and 2016–2017.<ref name="LNM">Template:Cite journal</ref><ref name="ENSO SA">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=Modoki-authorities/>
The recent discovery of ENSO Modoki has some scientists believing it to be linked to global warming.<ref name="Yeh2009">Template:Cite journal</ref> However, comprehensive satellite data go back only to 1979. More research must be done to find the correlation and study past El Niño episodes. More generally, there is no scientific consensus on how/if climate change might affect ENSO.<ref name="Collins10" />
There is also a scientific debate on the very existence of this "new" ENSO. A number of studies dispute the reality of this statistical distinction or its increasing occurrence, or both, either arguing the reliable record is too short to detect such a distinction,<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> finding no distinction or trend using other statistical approaches,<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> or that other types should be distinguished, such as standard and extreme ENSO.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Likewise, following the asymmetric nature of the warm and cold phases of ENSO, some studies could not identify similar variations for La Niña, both in observations and in the climate models,<ref>Template:Cite journal</ref> but some sources could identify variations on La Niña with cooler waters on central Pacific and average or warmer water temperatures on both eastern and western Pacific, also showing eastern Pacific Ocean currents going to the opposite direction compared to the currents in traditional La Niñas.<ref name="link.springer.com" /><ref name="auto" /><ref>Template:Cite journal</ref>
ENSO CosteroEdit
Coined by the Peruvian Template:Ill (ENFEN),<ref name=INOCAR>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> ENSO Costero, or ENSO Oriental, is the name given to the phenomenon where the sea-surface temperature anomalies are mostly focused on the South American coastline, especially from Peru and Ecuador.<ref name="IMARPE">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Studies point many factors that can lead to its occurrence,<ref name=Coastalvar>Template:Cite journal</ref> sometimes accompanying, or being accompanied, by a larger EP ENSO occurrence,<ref name="IMARPE" /> or even displaying opposite conditions from the observed ones in the other Niño regions when accompanied by Modoki variations.<ref name=PhD>Template:Cite thesis</ref>
ENSO Costero events usually present more localized effects, with warm phases leading to increased rainfall over the coast of Ecuador, northern Peru and the Amazon rainforest, and increased temperatures over the northern Chilean coast,<ref name=INOCAR/><ref name=Chile>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and cold phases leading to droughts on the Peruvian coast, and increased rainfall and decreased temperatures on its mountainous and jungle regions.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Because they don't influence the global climate as much as the other types, these events present lesser and weaker correlations to other significant ENSO features, neither always being triggered by Kelvin waves,<ref name=INOCAR/> nor always being accompanied by proportional Southern Oscillation responses.<ref>Template:Cite journal</ref> According to the Coastal Niño Index (ICEN), strong El Niño Costero events include 1957, 1982–83, 1997–98 and 2015–16, and La Niña Costera ones include 1950, 1954–56, 1962, 1964, 1966, 1967–68, 1970–71, 1975–76 and 2013.<ref name=ICEN>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Monitoring and declaration of conditionsEdit
Currently, each country has a different threshold for what constitutes an El Niño event, which is tailored to their specific interests, for example:<ref name="December 2014 EU2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- In the United States, an El Niño is declared when the Climate Prediction Center, which monitors the sea surface temperatures in the Niño 3.4 region and the tropical Pacific, forecasts that the sea surface temperature will be Template:Cvt above average or more for the next several seasons.<ref name="How?">{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref> The Niño 3.4 region stretches from the 120th to 170th meridians west longitude astride the equator five degrees of latitude on either side, are monitored. It is approximately Template:Convert to the southeast of Hawaii. The most recent three-month average for the area is computed, and if the region is more than 0.5 °C (0.9 °F) above (or below) normal for that period, then an El Niño (or La Niña) is considered in progress.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- The Australian Bureau of Meteorology looks at the trade winds, Southern Oscillation Index, weather models and sea surface temperatures in the Niño 3 and 3.4 regions, before declaring an ENSO event.<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- The Japan Meteorological Agency declares that an ENSO event has started when the average five month sea surface temperature deviation for the Niño 3 region is over Template:Convert for six consecutive months or longer.<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- The Peruvian government declares that an ENSO Costero is under way if the sea surface temperature deviation in the Niño 1+2 regions equal or exceed Template:Cvt for at least three months.<ref name=ICEN/>
- The United Kingdom's Met Office also uses a several month period to determine ENSO state.<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref> When this warming or cooling occurs for only seven to nine months, it is classified as El Niño/La Niña "conditions"; when it occurs for more than that period, it is classified as El Niño/La Niña "episodes".<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Effects of ENSO on global climateEdit
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In climate change science, ENSO is known as one of the internal climate variability phenomena. The other two main ones are Pacific decadal oscillation and Atlantic multidecadal oscillation.<ref name="IPCC2021" />Template:Rp
La Niña impacts the global climate and disrupts normal weather patterns, which can lead to intense storms in some places and droughts in others.<ref name="NIWA NZ">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> El Niño events cause short-term (approximately 1 year in length) spikes in global average surface temperature while La Niña events cause short term cooling.<ref name=":1">Template:Cite journal</ref> Therefore, the relative frequency of El Niño compared to La Niña events can affect global temperature trends on decadal timescales.<ref name=":2">Template:Cite journal</ref>
Climate changeEdit
There is no sign that there are actual changes in the ENSO physical phenomenon due to climate change. Climate models do not simulate ENSO well enough to make reliable predictions. Future trends in ENSO are uncertain<ref name="Collins102"/> as different models make different predictions.<ref name="Merryfield2006">Template:Cite journal</ref><ref name="Guilyardi2009">Template:Cite journal</ref> It may be that the observed phenomenon of more frequent and stronger El Niño events occurs only in the initial phase of the global warming, and then (e.g., after the lower layers of the ocean get warmer, as well), El Niño will become weaker.<ref name="Meehl2006">Template:Cite journal</ref> It may also be that the stabilizing and destabilizing forces influencing the phenomenonTemplate:Clarify will eventually compensate for each other.<ref name="Philip2006">Template:Cite journal</ref>
The consequences of ENSO in terms of the temperature anomalies and precipitation and weather extremes around the world are clearly increasing and associated with climate change. For example, recent scholarship (since about 2019) has found that climate change is increasing the frequency of extreme El Niño events.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref><ref name="Liu2022">Template:Cite journal</ref> Previously there was no consensus on whether climate change will have any influence on the strength or duration of El Niño events, as research alternately supported El Niño events becoming stronger and weaker, longer and shorter.<ref name="ENSO + Climate Change">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Collins102">Template:Cite journal</ref>
While much longer observation of ENSO is needed to robustly detect changes,<ref>Template:Cite journal</ref> a large ensemble experiment with multiple climate models shows an increase of approximately 10 % in eastern Pacific ENSO amplitude between the 1901–1960 and 1961–2020 periods of greenhouse-gas increase. Compared to centuries-long runs with pre-industrial GHG concentrations, the ensemble of 1961–2020 results shows twice the likelihood of strong eastern Pacific El Niño events and nine times the likelihood of strong central Pacific La Niña events.<ref>Template:Cite journal</ref>
The IPCC Sixth Assessment Report summarized the state of the art of research in 2021 into the future of ENSO as follows:
- "In the long term, it is very likely that the precipitation variance related to El Niño–Southern Oscillation will increase"<ref name="IPCC2021" />Template:Rp and
- "It is very likely that rainfall variability related to changes in the strength and spatial extent of ENSO teleconnections will lead to significant changes at regional scale".<ref name="IPCC2021" />Template:Rp and
- "There is medium confidence that both ENSO amplitude and the frequency of high-magnitude events since 1950 are higher than over the period from 1850 and possibly as far back as 1400".<ref name="IPCC2021" />Template:Rp
Investigations regarding tipping pointsEdit
The ENSO is considered to be a potential tipping element in Earth's climate.<ref>Template:Cite journal</ref> Global warming can strengthen the ENSO teleconnection and resulting extreme weather events.<ref>Template:Cite journal</ref> For example, an increase in the frequency and magnitude of El Niño events have triggered warmer than usual temperatures over the Indian Ocean, by modulating the Walker circulation.<ref>Template:Cite journal</ref> This has resulted in a rapid warming of the Indian Ocean, and consequently a weakening of the Asian Monsoon.<ref>Template:Cite journal</ref>
Effects of ENSO on weather patternsEdit
El Niño affects the global climate and disrupts normal weather patterns, which can lead to intense storms in some places and droughts in others.<ref name="NIWA El Niño/La Niña">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="How Much Do El Niño">Template:Cite journal</ref>
Tropical cyclonesEdit
Most tropical cyclones form on the side of the subtropical ridge closer to the equator, then move poleward past the ridge axis before recurving into the main belt of the Westerlies.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Areas west of Japan and Korea tend to experience many fewer September–November tropical cyclone impacts during El Niño and neutral years. During El Niño years, the breakTemplate:Clarify in the subtropical ridge tends to lie near 130°E, which would favor the Japanese archipelago.<ref name="China2">Template:Cite journal</ref>
Based on modeled and observed accumulated cyclone energy (ACE), El Niño years usually result in less active hurricane seasons in the Atlantic Ocean, but instead favor a shift to tropical cyclone activity in the Pacific Ocean, compared to La Niña years favoring above average hurricane development in the Atlantic and less so in the Pacific basin.<ref>Template:Cite journal</ref>
Over the Atlantic Ocean, vertical wind shear is increased, which inhibits tropical cyclone genesis and intensification, by causing the westerly winds to be stronger.<ref name="TC FAQ G2">Template:Cite book</ref> The atmosphere over the Atlantic Ocean can also be drier and more stable during El Niño events, which can inhibit tropical cyclone genesis and intensification.<ref name="TC FAQ G2" /> Within the Eastern Pacific basin: El Niño events contribute to decreased easterly vertical wind shear and favor above-normal hurricane activity.<ref name="EPAC Background">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> However, the impacts of the ENSO state in this region can vary and are strongly influenced by background climate patterns.<ref name="EPAC Background" /> The Western Pacific basin experiences a change in the location of where tropical cyclones form during El Niño events, with tropical cyclone formation shifting eastward, without a major change in how many develop each year.<ref name="TC FAQ G2" /> As a result of this change, Micronesia is more likely, and China less likely, to be affected by tropical cyclones.<ref name="China2" /> A change in the location of where tropical cyclones form also occurs within the Southern Pacific Ocean between 135°E and 120°W, with tropical cyclones more likely to occur within the Southern Pacific basin than the Australian region.<ref name="What is an El Niño?2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="TC FAQ G2" /> As a result of this change tropical cyclones are 50% less likely to make landfall on Queensland, while the risk of a tropical cyclone is elevated for island nations like Niue, French Polynesia, Tonga, Tuvalu, and the Cook Islands.<ref name="What is an El Niño?2" /><ref name="NIWA">Template:Cite press release</ref><ref>Template:Cite press release</ref>
Remote influence on tropical Atlantic OceanEdit
A study of climate records has shown that El Niño events in the equatorial Pacific are generally associated with a warm tropical North Atlantic in the following spring and summer.<ref>Template:Cite journal</ref> About half of El Niño events persist sufficiently into the spring months for the Western Hemisphere Warm Pool to become unusually large in summer.<ref>Template:Cite journal</ref> Occasionally, El Niño's effect on the Atlantic Walker circulation over South America strengthens the easterly trade winds in the western equatorial Atlantic region. As a result, an unusual cooling may occur in the eastern equatorial Atlantic in spring and summer following El Niño peaks in winter.<ref>Template:Cite journal</ref> Cases of El Niño-type events in both oceans simultaneously have been linked to severe famines related to the extended failure of monsoon rains.<ref name="Davis2001">Template:Cite book</ref>
Impacts on humans and ecosystemsEdit
Economic impactsEdit
When El Niño conditions last for many months, extensive ocean warming and the reduction in easterly trade winds limits upwelling of cold nutrient-rich deep water, and its economic effect on local fishing for an international market can be serious.<ref name="deadfish2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Developing countries that depend on their own agriculture and fishing, particularly those bordering the Pacific Ocean, are usually most affected by El Niño conditions. In this phase of the Oscillation, the pool of warm water in the Pacific near South America is often at its warmest in late December.<ref name="DFG2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
More generally, El Niño can affect commodity prices and the macroeconomy of different countries. It can constrain the supply of rain-driven agricultural commodities; reduce agricultural output, construction, and services activities; increase food prices; and may trigger social unrest in commodity-dependent poor countries that primarily rely on imported food.<ref name="University of Cambridge">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A University of Cambridge Working Paper shows that while Australia, Chile, Indonesia, India, Japan, New Zealand and South Africa face a short-lived fall in economic activity in response to an El Niño shock, other countries may actually benefit from an El Niño weather shock (either directly or indirectly through positive spillovers from major trading partners), for instance, Argentina, Canada, Mexico and the United States. Furthermore, most countries experience short-run inflationary pressures following an El Niño shock, while global energy and non-fuel commodity prices increase.<ref>Template:Cite journal</ref> The IMF estimates a significant El Niño can boost the GDP of the United States by about 0.5% (due largely to lower heating bills) and reduce the GDP of Indonesia by about 1.0%.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Health and social impactsEdit
Extreme weather conditions related to the El Niño cycle correlate with changes in the incidence of epidemic diseases. For example, the El Niño cycle is associated with increased risks of some of the diseases transmitted by mosquitoes, such as malaria, dengue fever, and Rift Valley fever.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Cycles of malaria in India, Venezuela, Brazil, and Colombia have now been linked to El Niño. Outbreaks of another mosquito-transmitted disease, Australian encephalitis (Murray Valley encephalitis—MVE), occur in temperate south-east Australia after heavy rainfall and flooding, which are associated with La Niña events. A severe outbreak of Rift Valley fever occurred after extreme rainfall in north-eastern Kenya and southern Somalia during the 1997–98 El Niño.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
ENSO conditions have also been related to Kawasaki disease incidence in Japan and the west coast of the United States,<ref name="Ballester">Template:Cite journal</ref> via the linkage to tropospheric winds across the north Pacific Ocean.<ref name="Rod">Template:Cite journal</ref>
ENSO may be linked to civil conflicts. Scientists at The Earth Institute of Columbia University, having analyzed data from 1950 to 2004, suggest ENSO may have had a role in 21% of all civil conflicts since 1950, with the risk of annual civil conflict doubling from 3% to 6% in countries affected by ENSO during El Niño years relative to La Niña years.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Ecological consequencesEdit
During the 1982–83, 1997–98 and 2015–16 ENSO events, large extensions of tropical forests experienced a prolonged dry period that resulted in widespread fires, and drastic changes in forest structure and tree species composition in Amazonian and Bornean forests. Their impacts do not restrict only vegetation, since declines in insect populations were observed after extreme drought and terrible fires during El Niño 2015–16.<ref>Template:Cite journal</ref> Declines in habitat-specialist and disturbance-sensitive bird species and in large-frugivorous mammals were also observed in Amazonian burned forests, while temporary extirpation of more than 100 lowland butterfly species occurred at a burned forest site in Borneo.
In seasonally dry tropical forests, which are more drought tolerant, researchers found that El Niño induced drought increased seedling mortality. In a research published in October 2022, researchers studied seasonally dry tropical forests in a national park in Chiang Mai in Thailand for 7 years and observed that El Niño increased seedling mortality even in seasonally dry tropical forests and may impact entire forests in long run.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Coral bleachingEdit
Following the El Nino event in 1997 – 1998, the Pacific Marine Environmental Laboratory attributes the first large-scale coral bleaching event to the warming waters.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Most critically, global mass bleaching events were recorded in 1997-98 and 2015–16, when around 75-99% losses of live coral were registered across the world. Considerable attention was also given to the collapse of Peruvian and Chilean anchovy populations that led to a severe fishery crisis following the ENSO events in 1972–73, 1982–83, 1997–98 and, more recently, in 2015–16. In particular, increased surface seawater temperatures in 1982-83 also lead to the probable extinction of two hydrocoral species in Panamá, and to a massive mortality of kelp beds along 600 km of coastline in Chile, from which kelps and associated biodiversity slowly recovered in the most affected areas even after 20 years. All these findings enlarge the role of ENSO events as a strong climatic force driving ecological changes all around the world – particularly in tropical forests and coral reefs.<ref>Template:Cite journal</ref>
Impacts by regionEdit
Observations of ENSO events since 1950 show that impacts associated with such events depend on the time of year.<ref name="Cascade2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> While certain events and impacts are expected to occur, it is not certain that they will happen.<ref name="Cascade2" /> The impacts that generally do occur during most El Niño events include below-average rainfall over Indonesia and northern South America, and above average rainfall in southeastern South America, eastern equatorial Africa, and the southern United States.<ref name="Cascade2" />
AfricaEdit
La Niña results in wetter-than-normal conditions in southern Africa from December to February, and drier-than-normal conditions over equatorial east Africa over the same period.<ref>Template:Cite news</ref>
The effects of El Niño on rainfall in southern Africa differ between the summer and winter rainfall areas. Winter rainfall areas tend to get higher rainfall than normal and summer rainfall areas tend to get less rain. The effect on the summer rainfall areas is stronger and has led to severe drought in strong El Niño events.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref>
Sea surface temperatures off the west and south coasts of South Africa are affected by ENSO via changes in surface wind strength.<ref name="Nhesvure 2020" >Nhesvure, B. (2020). Impacts of ENSO on coastal South African sea surface temperatures. Faculty of Science, Department of Oceanography. Retrieved from http://hdl.handle.net/11427/32954/ </ref> During El Niño the south-easterly winds driving upwelling are weaker which results in warmer coastal waters than normal, while during La Niña the same winds are stronger and cause colder coastal waters. These effects on the winds are part of large scale influences on the tropical Atlantic and the South Atlantic High-pressure system, and changes to the pattern of westerly winds further south. There are other influences not known to be related to ENSO of similar importance. Some ENSO events do not lead to the expected changes.<ref name="Nhesvure 2020" />
AntarcticaEdit
Many ENSO linkages exist in the high southern latitudes around Antarctica.<ref name="Turner2004">Template:Cite journal</ref> Specifically, El Niño conditions result in high-pressure anomalies over the Amundsen and Bellingshausen Seas, causing reduced sea ice and increased poleward heat fluxes in these sectors, as well as the Ross Sea. The Weddell Sea, conversely, tends to become colder with more sea ice during El Niño. The exact opposite heating and atmospheric pressure anomalies occur during La Niña.<ref name="Yuan2004">Template:Cite journal</ref> This pattern of variability is known as the Antarctic dipole mode, although the Antarctic response to ENSO forcing is not ubiquitous.<ref name="Yuan2004" />
AsiaEdit
In Western Asia, during the region's November–April rainy season, there is increased precipitation in the El Niño phase and reduced precipitation in the La Niña phase on average.<ref>Barlow, M., H. Cullen, and B. Lyon, 2002: Drought in central and southwest Asia: La Niña, the warm pool, and Indian Ocean precipitation. J. Climate, 15, 697–700</ref><ref>Nazemosadat, M. J., and A. R. Ghasemi, 2004: Quantifying the ENSO-related shifts in the intensity and probability of drought and wet periods in Iran. J. Climate, 17, 4005–4018</ref>
During El Niño years: As warm water spreads from the west Pacific and the Indian Ocean to the east Pacific, it takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific. Singapore experienced the driest February in 2010 since records began in 1869, with only 6.3 mm of rain falling in the month. The years 1968 and 2005 had the next driest Februaries, when 8.4 mm of rain fell.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
During La Niña years, the formation of tropical cyclones, along with the subtropical ridge position, shifts westward across the western Pacific Ocean, which increases the landfall threat in China.<ref name="China">Template:Cite journal</ref> In March 2008, La Niña caused a drop in sea surface temperatures over Southeast Asia by Template:Cvt. It also caused heavy rains over the Philippines, Indonesia, and Malaysia.<ref>Template:Cite news</ref>
AustraliaEdit
Across most of the continent, El Niño and La Niña have more impact on climate variability than any other factor. There is a strong correlation between the strength of La Niña and rainfall: the greater the sea surface temperature and Southern Oscillation difference from normal, the larger the rainfall change.<ref>Template:Cite journal</ref>
During El Niño events, the shift in rainfall away from the Western Pacific may mean that rainfall across Australia is reduced.<ref name="What is an El Niño?">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Over the southern part of the continent, warmer than average temperatures can be recorded as weather systems are more mobile and fewer blocking areas of high pressure occur.<ref name="What is an El Niño?" /> The onset of the Indo-Australian Monsoon in tropical Australia is delayed by two to six weeks, which as a consequence means that rainfall is reduced over the northern tropics.<ref name="What is an El Niño?" /> The risk of a significant bushfire season in south-eastern Australia is higher following an El Niño event, especially when it is combined with a positive Indian Ocean Dipole event.<ref name="What is an El Niño?" />
EuropeEdit
El Niño's effects on Europe are controversial, complex and difficult to analyze, as it is one of several factors that influence the weather over the continent and other factors can overwhelm the signal.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref>
North AmericaEdit
Template:See also La Niña causes mostly the opposite effects of El Niño: above-average precipitation across the northern Midwest, the northern Rockies, Northern California, and the Pacific Northwest's southern and eastern regions.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Meanwhile, precipitation in the southwestern and southeastern states, as well as southern California, is below average.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This also allowsTemplate:Clarify for the development of many stronger-than-average hurricanes in the Atlantic and fewer in the Pacific.
ENSO is linked to rainfall over Puerto Rico.Template:Clarify<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> During an El Niño, snowfall is greater than average across the southern Rockies and Sierra Nevada mountain range, and is well-below normal across the Upper Midwest and Great Lakes states. During a La Niña, snowfall is above normal across the Pacific Northwest and western Great Lakes.<ref>Climate Prediction Center. ENSO Impacts on United States Winter Precipitation and Temperature. Template:Webarchive Retrieved on 2008-04-16.</ref>
In Canada, La Niña will, in general, cause a cooler, snowier winter, such as the near-record-breaking amounts of snow recorded in the La Niña winter of 2007–2008 in eastern Canada.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="cpc.noaa.gov">Template:Cite report</ref>
In the spring of 2022, La Niña caused above-average precipitation and below-average temperatures in the state of Oregon. April was one of the wettest months on record, and La Niña effects, while less severe, were expected to continue into the summer.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Over North America, the main temperature and precipitation impacts of El Niño generally occur in the six months between October and March.<ref name="ENSO:Impacts">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="climate impacts">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In particular, the majority of Canada generally has milder than normal winters and springs, with the exception of eastern Canada where no significant impacts occur.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Within the United States, the impacts generally observed during the six-month period include wetter-than-average conditions along the Gulf Coast between Texas and Florida, while drier conditions are observed in Hawaii, the Ohio Valley, Pacific Northwest and the Rocky Mountains.<ref name="ENSO:Impacts" />
Study of more recent weather events over California and the southwestern United States indicate that there is a variable relationship between El Niño and above-average precipitation, as it strongly depends on the strength of the El Niño event and other factors.<ref name="ENSO:Impacts" /> Though it has been historically associated with high rainfall in California, the effects of El Niño depend more strongly on the "flavor"Template:Clarify of El Niño than its presence or absence, as only "persistent El Niño" events lead to consistently high rainfall.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref>
To the north across Alaska, La Niña events lead to drier than normal conditions, while El Niño events do not have a correlation towards dry or wet conditions. During El Niño events, increased precipitation is expected in California due to a more southerly, zonal, storm track.<ref>Monteverdi, John and Jan Null. Western Region Technical Attachment No. 97-37 November 21, 1997: El Niño and California Precipitation. Template:Webarchive Retrieved on 2008-02-28.</ref> During La Niña, increased precipitation is diverted into the Pacific Northwest due to a more northerly storm track.<ref>Mantua, Nathan. La Niña Impacts in the Pacific Northwest. Template:Webarchive Retrieved on 2008-02-29.</ref> During La Niña events, the storm track shifts far enough northward to bring wetter than normal winter conditions (in the form of increased snowfall) to the Midwestern states, as well as hot and dry summers.<ref>Reuters. La Nina could mean dry summer in Midwest and Plains. Template:Webarchive Retrieved on 2008-02-29.</ref> During the El Niño portion of ENSO, increased precipitation falls along the Gulf coast and Southeast due to a stronger than normal, and more southerly, polar jet stream.<ref>Climate Prediction Center. El Niño (ENSO) Related Rainfall Patterns Over the Tropical Pacific. Template:Webarchive Retrieved on 2008-02-28.</ref>
Isthmus of TehuantepecEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}}
The synoptic condition for the Tehuantepecer, a violent mountain-gap wind in between the mountains of Mexico and Guatemala, is associated with high-pressure system forming in Sierra Madre of Mexico in the wake of an advancing cold front, which causes winds to accelerate through the Isthmus of Tehuantepec. Tehuantepecers primarily occur during the cold season months for the region in the wake of cold fronts, between October and February, with a summer maximum in July caused by the westward extension of the Azores-Bermuda high pressure system. Wind magnitude is greater during El Niño years than during La Niña years, due to the more frequent cold frontal incursions during El Niño winters.<ref>Template:Cite journal</ref> Tehuantepec winds reach Template:Convert to Template:Convert, and on rare occasions Template:Convert. The wind's direction is from the north to north-northeast.<ref name="gloss">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It leads to a localized acceleration of the trade winds in the region, and can enhance thunderstorm activity when it interacts with the Intertropical Convergence Zone.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The effects can last from a few hours to six days.<ref name="MWL1971">Template:Cite journal</ref> Between 1942 and 1957, La Niña had an impact that caused isotope changes in the plants of Baja California, and that had helped scientists to study his impact.<ref>Template:Cite journal</ref>
Pacific islandsEdit
During an El Niño event, New Zealand tends to experience stronger or more frequent westerly winds during their summer, which leads to an elevated risk of drier than normal conditions along the east coast.<ref name="New Zealand El Niño's impacts">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> There is more rain than usual though on New Zealand's West Coast, because of the barrier effect of the North Island mountain ranges and the Southern Alps.<ref name="New Zealand El Niño's impacts" />
Fiji generally experiences drier than normal conditions during an El Niño, which can lead to drought becoming established over the Islands.<ref name="Fiji ENSO Update">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> However, the main impacts on the island nation is felt about a year after the event becomes established.<ref name="Fiji ENSO Update" /> Within the Samoan Islands, below average rainfall and higher than normal temperatures are recorded during El Niño events, which can lead to droughts and forest fires on the islands.<ref name="Clim Jan 2016">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Other impacts include a decrease in the sea level, possibility of coral bleaching in the marine environment and an increased risk of a tropical cyclone affecting Samoa.<ref name="Clim Jan 2016" />
In the late winter and spring during El Niño events, drier than average conditions can be expected in Hawaii.<ref>Chu, Pao-Shin. Hawaii Rainfall Anomalies and El Niño. Retrieved on 2008-03-19.</ref> On Guam during El Niño years, dry season precipitation averages below normal, but the probability of a tropical cyclone is more than triple what is normal, so extreme short duration rainfall events are possible.<ref>Pacific ENSO Applications Climate Center. Pacific ENSO Update: 4th Quarter, 2006. Vol. 12 No. 4. Template:Webarchive Retrieved on 2008-03-19.</ref> On American Samoa during El Niño events, precipitation averages about 10 percent above normal, while La Niña events are associated with precipitation averaging about 10 percent below normal.<ref>Pacific ENSO Applications Climate Center. RAINFALL VARIATIONS DURING ENSO. Template:Webarchive Retrieved on 2008-03-19.</ref>
South AmericaEdit
The effects of El Niño in South America are direct and strong. An El Niño is associated with warm and very wet weather months in April–October along the coasts of northern Peru and Ecuador, causing major flooding whenever the event is strong or extreme.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Because El Niño's warm pool feeds thunderstorms above, it creates increased rainfall across the east-central and eastern Pacific Ocean, including several portions of the South American west coast. The effects of El Niño in South America are direct and stronger than in North America. An El Niño is associated with warm and very wet weather months in April–October along the coasts of northern Peru and Ecuador, causing major flooding whenever the event is strong or extreme.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The effects during the months of February, March, and April may become critical along the west coast of South America, El Niño reduces the upwelling of cold, nutrient-rich water that sustains large fish populations, which in turn sustain abundant sea birds, whose droppings support the fertilizer industry. The reduction in upwelling leads to fish kills off the shore of Peru.<ref name="deadfish">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The local fishing industry along the affected coastline can suffer during long-lasting El Niño events. Peruvian fisheries collapsed during the 1970s due to overfishing following the 1972 El Niño Peruvian anchoveta reduction.<ref name="perufish">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The fisheries were previously the world's largest, however, this collapse led to the decline of these fisheries. During the 1982–83 event, jack mackerel and anchoveta populations were reduced, scallops increased in warmer water, but hake followed cooler water down the continental slope, while shrimp and sardines moved southward, so some catches decreased while others increased.<ref name="Pearcy1987">Template:Cite journal</ref> Horse mackerel have increased in the region during warm events. Shifting locations and types of fish due to changing conditions create challenges for the fishing industry. Peruvian sardines have moved during El Niño events to Chilean areas. Other conditions provide further complications, such as the government of Chile in 1991 creating restrictions on the fishing areas for self-employed fishermen and industrial fleets.
Southern Brazil and northern Argentina also experience wetter than normal conditions during El Niño years, but mainly during the spring and early summer. Central Chile receives a mild winter with large rainfall, and the Peruvian-Bolivian Altiplano is sometimes exposed to unusual winter snowfall events. Drier and hotter weather occurs in parts of the Amazon River Basin, Colombia, and Central America.<ref>Template:Cite book</ref>
During a time of La Niña, drought affects the coastal regions of Peru and Chile.<ref name="GLOBE">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> From December to February, northern Brazil is wetter than normal.<ref name="GLOBE" /> La Niña causes higher than normal rainfall in the central Andes, which in turn causes catastrophic flooding on the Llanos de Mojos of Beni Department, Bolivia. Such flooding is documented from 1853, 1865, 1872, 1873, 1886, 1895, 1896, 1907, 1921, 1928, 1929 and 1931.<ref>Template:Cite book</ref>
Galápagos IslandsEdit
The Galápagos Islands are a chain of volcanic islands, nearly 600 miles west of Ecuador, South America.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> in the Eastern Pacific Ocean. These islands support a wide diversity of terrestrial and marine species.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The ecosystem is based on the normal trade winds which influence upwelling of cold, nutrient rich waters to the islands.<ref>Template:Cite journal</ref> During an El Niño event the trade winds weaken and sometimes blow from west to east, which causes the Equatorial current to weaken, raising surface water temperatures and decreasing nutrients in waters surrounding the Galápagos. El Niño causes a trophic cascade which impacts entire ecosystems starting with primary producers and ending with critical animals such as sharks, penguins, and seals.<ref>Template:Cite journal</ref> The effects of El Niño can become detrimental to populations that often starve and die back during these years. Rapid evolutionary adaptations are displayed amongst animal groups during El Niño years to mitigate El Niño conditions.<ref>Template:Cite journal</ref>
HistoryEdit
In geologic timescalesEdit
Evidence is also strong for El Niño events during the early Holocene epoch 10,000 years ago.<ref name=":0" /> Different modes of ENSO-like events have been registered in paleoclimatic archives, showing different triggering methods, feedbacks and environmental responses to the geological, atmospheric and oceanographic characteristics of the time. These paleorecords can be used to provide a qualitative basis for conservation practices.<ref>Template:Cite journal</ref>
Scientists have also found chemical signatures of warmer sea surface temperatures and increased rainfall caused by El Niño in coral specimens that are around 13,000 years old.<ref name="Weather Underground" />
In a paleoclimate study published in 2024, the authors suggest that El Niños had a strong influence on Earth's hothouse climate during the Permian-Triassic extinction event. The increasing intensity and duration of El Niño events were associated with active volcanism, which resulted in the dieback of vegetation, an increase in the amount of carbon dioxide in the atmosphere, a significant warming and disturbances in the circulation of air masses.<ref name=Sun2024>Template:Cite journal</ref>
| Series/ epoch | Age of archive / Location / Type of archive or proxy | Description and references |
|---|---|---|
| Mid Holocene | 4150 ya / Vanuatu Islands / Coral core | Coral bleaching in Vanuatu coral records, indication of shoaling of thermocline, is analyzed for Sr/Ca and U/Ca content, from which temperature is regressed. The temperature variability shows that during the mid-Holocene, changes in the position of the anticyclonic gyre produced average to cold (La Niña) conditions, which were probably interrupted by strong warm events (El Niño), which might have produced the bleaching, associated to decadal variability.<ref>Template:Cite journal</ref> |
| Holocene | 12000ya / Bay of Guayaquil, Ecuador / Pollen content of marine core | Pollen records show changes in precipitation, possibly related to variability of the position of the ITCZ, as well as the latitudinal maxima of the Humboldt Current, which both depend on ENSO frequency and amplitude variability. Three different regimes of ENSO influence are found in the marine core.<ref>Template:Cite journal</ref> |
| Holocene | 12000ya /
Pallcacocha Lake, Ecuador / Sediment core |
Core shows warm events with periodicities of 2–8 years, which become more frequent over the Holocene until about 1,200 years ago, and then decline, on top of which there are periods of low and high ENSO-related events, possibly due to changes in insolation.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> |
| LGM | 45000ya / Australia / Peat core | Moisture variability in the Australian core shows dry periods related to frequent warm events (El Niño), correlated to DO events. Although no strong correlation was found with the Atlantic Ocean, it is suggested that the insolation influence probably affected both oceans, although the Pacific Ocean seems to have the most influence on teleconnection in annual, millennial and semi-precessional timescales.<ref>Template:Cite journal</ref> |
| Pleistocene | 240 Kya / Indian and Pacific oceans / Coccolithophore in 9 deep sea cores | 9 deep cores in the equatorial Indian and Pacific show variations in primary productivity, related to glacial-interglacial variability and precessional periods (23 ky) related to changes in the thermocline. There is also indication that the equatorial areas can be early responders to insolation forcing.<ref>Template:Cite journal</ref> |
| Pliocene | 2.8 Mya / Spain / Lacustrine laminated sediments core | The basin core shows light and dark layers, related to summer/autumn transition where more/less productivity is expected. The core shows thicker or thinner layers, with periodicities of 12, 6–7 and 2–3 years, related to ENSO, North Atlantic Oscillation (NAO) and Quasi-biennial Oscillation (QBO), and possibly also insolation variability (sunspots).<ref>Template:Cite journal</ref> |
| Pliocene | 5.3 Mya / Equatorial Pacific / Foraminifera in deep sea cores | Deep sea cores at ODP site 847 and 806 show that the Pliocene warm period presented permanent El Niño-like conditions, possibly related to changes in the mean state of extratropical regions<ref>Template:Cite journal</ref> or changes in ocean heat transport resulting from increased tropical cyclone activity.<ref>Template:Cite journal</ref> |
| Miocene | 5.92-5.32 Mya / Italy / Evaporite varve thickness | The varve close to the Mediterranean shows 2–7 year variability, closely related to ENSO periodicity. Model simulations show that there is more correlation with ENSO than NAO, and that there is a strong teleconnection with the Mediterranean due to lower gradients of temperature.<ref>Template:Cite journal</ref> |
During human historyEdit
ENSO conditions have occurred at two- to seven-year intervals for at least the past 300 years, but most of them have been weak.<ref name=":0">Template:Cite journal</ref>
El Niño may have led to the demise of the Moche and other pre-Columbian Peruvian cultures.<ref>Template:Cite book</ref> A recent study suggests a strong El Niño effect between 1789 and 1793 caused poor crop yields in Europe, which in turn helped touch off the French Revolution.<ref name="Grove1998">Template:Cite journal</ref> The extreme weather produced by El Niño in 1876–77 gave rise to the most deadly famines of the 19th century.<ref>Template:Cite book</ref> The 1876 famine alone in northern China killed up to 13 million people.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The phenomenon had long been of interest because of its effects on the guano industry and other enterprises that depend on biological productivity of the sea. It is recorded that as early as 1822, cartographer Joseph Lartigue, of the French frigate La Clorinde under Baron Mackau, noted the "counter-current" and its usefulness for traveling southward along the Peruvian coast.<ref>Template:Cite book From pp. 22–23: "Il est néanmoins nécessaire, au sujet de cette règle générale, de faire part d'une exception ... dépassé le port de sa destination de plus de 2 ou 3 lieues; ... " (It is nevertheless necessary, with regard to this general rule, to announce an exception which, in some circumstances, might shorten the sailing. One said above that the breeze was sometimes quite fresh [i.e., strong], and that then the counter-current, which bore southward along the land, stretched some miles in length; it is obvious that one will have to tack in this counter-current, whenever the wind's force will permit it and whenever one will not have gone past the port of one's destination by more than 2 or 3 leagues; ...)</ref><ref name="pezet">Template:Citation</ref><ref>Template:Cite book</ref>
Charles Todd, in 1888, suggested droughts in India and Australia tended to occur at the same time;<ref>"Droughts in Australia: Their causes, duration, and effect: The views of three government astronomers [R.L.J. Ellery, H.C. Russell, and C. Todd]," The Australasian (Melbourne, Victoria), 29 December 1888, pp. 1455–1456. From p. 1456: Template:Webarchive "Australian and Indian Weather" : "Comparing our records with those of India, I find a close correspondence or similarity of seasons with regard to the prevalence of drought, and there can be little or no doubt that severe droughts occur as a rule simultaneously over the two countries."</ref> Norman Lockyer noted the same in 1904.<ref>Lockyer, N. and Lockyer, W.J.S. (1904) "The behavior of the short-period atmospheric pressure variation over the Earth's surface," Template:Webarchive Proceedings of the Royal Society of London, 73 : 457–470.</ref> An El Niño connection with flooding was reported in 1894 by Victor Eguiguren (1852–1919) and in 1895 by Federico Alfonso Pezet (1859–1929).<ref>Eguiguren, D. Victor (1894) "Las lluvias de Piura" Template:Webarchive (The rains of Piura), Boletín de la Sociedad Geográfica de Lima, 4 : 241–258. [in Spanish] From p. 257: "Finalmente, la época en que se presenta la corriente de Niño, es la misma de las lluvias en aquella región." (Finally, the period in which the El Niño current is present is the same as that of the rains in that region [i.e., the city of Piura, Peru].)</ref><ref name="pezet" /><ref>Pezet, Federico Alfonso (1896) "La contra-corriente "El Niño", en la costa norte de Perú" Template:Webarchive (The counter-current "El Niño", on the northern coast of Peru), Boletín de la Sociedad Geográfica de Lima, 5 : 457-461. [in Spanish]</ref> In 1924, Gilbert Walker (for whom the Walker circulation is named) coined the term "Southern Oscillation".<ref>Walker, G. T. (1924) "Correlation in seasonal variations of weather. IX. A further study of world weather," Memoirs of the Indian Meteorological Department, 24 : 275–332. From p. 283: "There is also a slight tendency two quarters later towards an increase of pressure in S. America and of Peninsula [i.e., Indian] rainfall, and a decrease of pressure in Australia : this is part of the main oscillation described in the previous paper* which will in future be called the 'southern' oscillation." Available at: Royal Meteorological Society Template:Webarchive</ref> He and others (including Norwegian-American meteorologist Jacob Bjerknes) are generally credited with identifying the El Niño effect.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The major 1982–83 El Niño led to an upsurge of interest from the scientific community. The period 1990–95 was unusual in that El Niños have rarely occurred in such rapid succession.<ref>Template:Cite journal</ref><ref>Template:Cite thesis</ref>Template:Unreliable source<ref name="Trenberth19962">Template:Cite journal</ref> An especially intense El Niño event in 1998 caused an estimated 16% of the world's reef systems to die. The event temporarily warmed air temperature by 1.5 °C, compared to the usual increase of 0.25 °C associated with El Niño events.<ref name="Trenberth">Template:Cite journal</ref> Since then, mass coral bleaching has become common worldwide, with all regions having suffered "severe bleaching".<ref name="Marshall2006">Template:Cite book</ref>
Around 1525, when Francisco Pizarro made landfall in Peru, he noted rainfall in the deserts, the first written record of the impacts of El Niño.<ref name="Weather Underground">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Related patternsEdit
Madden–Julian oscillationEdit
Link to the El Niño-Southern oscillationEdit
Pacific decadal oscillationEdit
MechanismsEdit
Pacific Meridional ModeEdit
See alsoEdit
For La Niña:
- 2000 Mozambique flood (attributed to La Niña)
- 2010 Pakistan floods (attributed to La Niña)
- 2010–2011 Queensland floods (attributed to La Niña)
- 2010–2012 La Niña event
- 2010–2011 Southern Africa floods (attributed to La Niña)
- 2010–2013 Southern United States and Mexico drought (attributed to La Niña)
- 2011 East Africa drought (attributed to La Niña)
- 2020 Atlantic hurricane season (unprecedented severity fueled by La Niña)
- 2021 eastern Australia floods (severity fueled by La Niña)
- 2022 Suriname floods (attributed to La Niña)
- 2023 Auckland Anniversary Weekend floods (attributed to La Niña)
- 2020–2023 La Niña event
For El Niño:
- 1982–83 El Niño event
- 1997 Pacific hurricane season (severity fueled by El Niño)
- 1997–98 El Niño event
- 2014–2016 El Niño event
- 2015 Pacific hurricane season (severity fueled by El Niño)
- 2023–2024 El Niño event
ReferencesEdit
External linksEdit
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|CitationClass=web }} Provides current phase of ENSO according to the Australian interpretation.
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