El Nino

Extracted Attributes

El Niño–Southern Oscillation

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. 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. El Niño events can be more intense but La Niña events may repeat and last longer. El Niño events, on average, reduced Panama Canal Water Times–contrary to belief. 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. 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. 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. Therefore, the relative frequency of El Niño compared to La Niña events can affect global temperature trends on timescales of around ten years. 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. Future trends in ENSO due to climate change are uncertain, 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". 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".

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• El Niño–Southern Oscillation

  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 El Niño–Southern Oscillation is a single climate phenomenon that quasi-periodically fluctuates between three phases: Neutral, La Niña or El Niño.( 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.( 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 [...] The El Niño–Southern Oscillation is a single climate phenomenon that periodically fluctuates between three phases: Neutral, La Niña or El Niño.( 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.(

• The Global Impacts of El Niño | Water Resources Research Center

  El Niño is the warm phase of ENSO (El Niño-Southern Oscillation), which is a periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean. The cool phase is known as La Niña. El Niño warming occurs, on average, every two to seven years. [...] Historical records of previous El Niño events suggest that the likelihood of the current El Niño being followed by La Niña is the same as a return to neutral conditions, during the second half of 2016. El Niño and La Niña events typically only last for nine to twelve months and re-occur every two to four years. Flip-flops from a strong El Niño to La Niña are not unusual. Should it occur, a La Niña could exacerbate the negative effects in countries that have experienced El Niño conditions. [...] The 2015-2016 El Niño event comes on top of volatile and erratic weather patterns linked to climate change; 2014 and 2015 were the hottest years on record, with the Pacific Ocean already warming to an unprecedented degree. Evidence is emerging that climate change will increase the odds of stronger El Niño (and la Niña) events according to the World Meteorological Organization.

• El Niño weakens but impacts continue

  The current El Niño event, which developed in June 2023, was at its strongest between November and January. It displayed a peak value of about 2.0 °C above the 1991 to 2020 average sea surface temperature for the eastern and central tropical Pacific Ocean. This made it one of the five strongest El Nino events ever, though it was weaker than the 1997/98 and 2015/2016 events. [...] El Niño is mainly a seasonal climate phenomenon with climate impacts on seasonal climate averages but can make extreme weather and climate-events more likely in certain regions. Furthermore, the seasonal forecasts are found to be more accurate during El Niño and La Niña events, particularly in the tropics, and this emphasizes the pivotal role of early warnings to support decision-making and enhance preparedness and anticipatory action. [...] El Niño occurs on average every two to seven years, and typically last nine to 12 months. It is a naturally occurring climate pattern associated with warming of the ocean surface in the central and eastern tropical Pacific Ocean. It influences weather and storm patterns in different parts of the world. But it takes place in the context of a climate being changed by human activities.

• What are El Nino and La Nina? - NOAA's National Ocean Service

  El Niño means Little Boy in Spanish. South American fishermen first noticed periods of unusually warm water in the Pacific Ocean in the 1600s. The full name they used was El Niño de Navidad, because El Niño typically peaks around December.

• El Niño & La Niña (El Niño-Southern Oscillation)

  Image 7: A pair of stacked maps showing the common impacts of El Nino and La Nina on winter (December through February) climate across the globe. Different colors indicate if an area is more likely to be cool, warm, wet, dry, cool and dry, warm and dry, cool and wet, or warm and wet, compared to average. [...] El Niño and La Niña are the warm and cool phases of a natural climate pattern across the tropical Pacific known as the El Niño-Southern Oscillation, or “ENSO” for short. The pattern shifts back and forth irregularly every two to seven years, bringing predictable changes in ocean temperature and disrupting the normal wind and rainfall patterns across the tropics. These changes in the seasonal climate of the world's biggest ocean have a cascade of global side effects. #### More About el Niño