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How El Niño and Climate Change are Related

Jacob Greenlee

Despite its name, there is nothing little about El Niño. Originally named “El Niño de Navidad” in Spanish, the name means “The Little Boy,” after South American fishermen who noticed periods of unusually warm water in December associating it with the time of Christian nativity. El Niño is one of the most significant climate events around the world. This climate phenomenon occurs every couple of years and drastically affects the environment. El Niño is poised to become stronger and more volatile with ongoing climate change, which may have lasting effects on the environment, belying its name. In fact, an El Niño event is expected to happen later this year.

El Niño is the periodic warming of water temperatures around the central-eastern Pacific Ocean. The phenomenon relies heavily on wind systems. During periods of normal atmospheric activity, trade winds blow westward, bringing less dense, warm water toward Southeastern Asia. Like a conveyor belt, as warm water slides west, denser, cooler water is brought east underneath and forced upwards along the western coast of South America, in a process known as upwelling. This places warm water to the west and colder water to the east. During an El Niño event, the trend reverses; weakening trade winds prevent the flow of warm water to Asia, allowing it to pool in the eastern Pacific Ocean, off the western coast of South America. El Niño is formally defined as an increase in water temperature 0.5 degrees celsius above average.

The phenomenon works in conjunction with its twin phenomenon, La Niña, which is essentially the opposite. During La Niña, stronger trade winds intensify the transport of warmer water to the west more than usual and increase the upwelling of colder water eastward, decreasing the water temperature instead. In March 2023, the UN declared that an unusually long La Niña event that started in 2020 was ending, implying the impending arrival of El Niñno later this year or early next year. The UN predicts a 55% chance of El Niño occurring in June through August.

El Niño has a major effect on the environment. Warmer water temperatures heat up the air, causing evaporation and increasing moisture in the air which create volatile weather conditions like storms. Because warmer water is pooled to the east during El Niño, storms increase the risk of flooding in countries like Peru and parts of the southern US, experiencing wetter weather. In the meantime, droughts may occur in countries to the west that subsequently experience relatively lesser rainfall and hotter temperatures, like Indonesia and Australia. This decrease in rainfall towards the west increases the chance of heatwaves in countries like India, hurting rice production across the region. In fact, a particularly strong El Niño in 2015 induced a marine heat wave that killed over half of the corals in the northern part of the Great Barrier Reef, the most devastating coral bleaching event in history. Additionally, because the upwelling of colder water weakens during El Niño, the pooling of warmer water attracts tropical fish like yellowtail and albacore tuna that normally cannot live in cooler temperatures. However, the lack of nutrient-rich cold water decreases the amount of phytoplankton off the South American coast. This decreases the food supply for fish that eat the plankton, and anything that eats the fish.

However, the greatest impact of El Niño will be on climate change. El Niño has the possibility to break the 1.5 degrees Celsius maximum temperature change threshold above pre-industrial levels established by the 2015 Paris Agreement. The effects of El Niño tend to peak around December, but because of the time it takes to affect the globe, 2024 may be the year that humanity passes the 1.5 degrees Celsius benchmark. The 1.5 degrees Celsius limit is what scientists consider the tipping point for massive effects of climate change, including the melting of ice sheets in Greenland and the Antarctic, melting permafrost in the Arctic, or the slowing of the Gulf Stream. Additionally, forest fires caused by the increased heat of El Niño in the Amazon Rainforest may release the incredible amounts of carbon sequestered in the trees, substantially increasing carbon emissions. While El Niño is a natural phenomenon, its harmful consequences are exacerbated by human activity. If carbon emissions continue and steps aren’t taken to prevent them on a dedicated scale, El Niño may be only one of several factors accelerating climate change.


  1. Dareen, Seher. "US forecaster says El Nino could arrive by summer 2023" Reuters. March 9, 2023

  2. Meredith, Sam. "The return of El Nino could make the world even hotter — endangering a critical climate threshold" CNBC. Feb. 10, 2023

  3. Millard, Robin. "La Nina ending but warming El Nino may strike soon: UN" March 1, 2023

  4. Morton, Adam. "Stronger El Niño events may speed up irreversible melting of Antarctic ice, research finds" The Guardian. Feb. 21, 2023

  5. NOAA. "What are El Niño and La Niña?" Feb. 2, 2023

  6. Yoder, Kate. "A looming El Niño could give us a preview of life at 1.5C of warming" Grist. Feb. 24, 2023


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