El Niño: Development and effects of the climate phenomenon

For centuries, a natural climate phenomenon has occurred roughly every three to five years, leading to extreme weather changes in different parts of the world: Where there is normally drought, the climate phenomenon "El Niño" causes rainfall and in regions where it usually rains a lot, it brings drought. These climate anomalies can have serious consequences for agriculture, the water supply and the health of millions of people.

Historical El Niño events, such as the 2015/2016 phenomenon, clearly show how devastating the consequences can be for the affected communities. In view of the increasing threat posed by climate change, it is more important than ever to understand El Niño and prepare for the recurring event in the best possible way.

What is El Niño?

Hundreds of years ago, fishermen off the coast of Peru noticed that the sea became unusually warm at irregular intervals and fishing yields declined. They gave the phenomenon the name "El Niño", which literally translates from Spanish as "the boy". This is an allusion to the Christ Child, as fishermen often observed the phenomenon in South America around Christmas time. The first records of this climatic phenomenon date back to the first half of the 18th century. However, researchers suspect that El Niño was already having devastating consequences in the 7th century. Today we know that El Niño is a natural climate phenomenon in which the surface water in the central-eastern Pacific warms up considerably causing the overlying air circulation to reverse. This has major effects on local weather patterns: Heavy rainfall, droughts and heatwaves affect the surrounding continents. However, the indirect consequences of El Niño can also be found in Europe.

Researchers are not yet able to say with certainty what exactly triggers El Niño. The climate phenomenon is therefore difficult to predict and varies in intensity and duration each time. However, the global impact of El Niño can affect the livelihoods of millions of people, as crop yields are threatened and the risk of forest fires increases, among other things. Therefore, monitoring and understanding the phenomenon plays a crucial role in preparing for and mitigating potential impacts on affected areas.

Causes: Why does El Niño occur?

Trade winds normally blow from east to west over the equatorial Pacific, driving warm surface water from the coast of South America towards Indonesia and Australia. At the same time, cold, nutrient-rich water rises in the ocean off South America. In this normal state, the temperature difference between the central-eastern and western Pacific is around ten degrees. This is why the eastern Pacific is always colder than the western Pacific. In the west, heavy rainfall naturally occurs in combination with the trade winds, while it is usually dry in the coastal regions of Latin America. This entire process is part of the Walker circulation.

During the El Niño phenomenon, the trade winds weaken or reverse completely for unexplained reasons, so that the warm water spreads eastwards instead of westwards and accumulates off South America. The cold water from the depths of the ocean off South America cannot rise through the carpet of warm surface water, resulting in above-average warming of the eastern Pacific. As plankton dies off when temperatures are too high, the schools of fish off the coast of South America also disappear. However, the change in sea surface temperature has even more widespread effects and leads to global weather changes.

The exact causes for the occurrence of an El Niño event are complex and the subject of current research. In contrast to sudden geological events that trigger tsunamis, for example, El Niño builds up over months and can last from several months to over a year. Nevertheless, accurately predicting El Niño remains a challenge, as each event varies in intensity, duration and impact.

El Niño is usually followed by La Niña

While El Niño causes warmer temperatures worldwide and extreme drought in some regions, La Niña is the opposite climate phenomenon. La Niña (Spanish for "the girl") is part of the El Niño/Southern Oscillation (ENSO) cycle and typically occurs after a transitional/normal phase following El Niño. During the La Niña cold anomaly, the normal flow conditions prevail – albeit in an extreme form. During La Niña, it is even warmer and wetter in the west and drier than usual in the east. The La Niña phenomenon is followed by a normal phase until El Niño sets in again and the ENSO cycle begins again.

Risk areas: These regions are most affected by El Niño

Archive: Brenda Mulama/Malteser International

El Niño influences the weather worldwide. However, some regions are more vulnerable to the direct and indirect effects of the climate anomaly. These include areas in proximity to the coasts of the equatorial Pacific. However, the climatic effects of the weather phenomenon can also be felt in other countries:

South America's west coast: Peru and Ecuador are especially prone to heavy rainfall during an El Niño event, which leads to flooding and landslides. The unusual warming of the Pacific also has a negative impact on fish stocks and therefore on the fishing industry. Chile, on the other hand, is frequently affected by severe drought.
Australia and Indonesia: In these regions, El Niño often leads to extreme drought, which frequently results in forest fires.
Southern Africa: Countries such as South Africa, Botswana and Namibia can experience droughts in an El Niño year, which put a strain on water resources and trigger hunger crises.
North and Central America: In the south of the USA and in Mexico, there is often increased rainfall and flooding.
India: South Asia usually experiences dryness and drought during El Niño.

Even if the effects of El Niño are much smaller in Europe, the long-distance effects of the climate phenomenon can also be felt here. Researchers suspect that El Niño could lead to more severe cold snaps in Central Europe, for example

The consequences of El Niño for people

The consequences of the El Niño climate phenomenon are diverse and depend on the intensity and duration of the anomaly. The effects range from regional to global chain reactions on the weather, the environment, the economy, human health and safety.

Changing rainfall patterns: El Niño can lead to two extreme weather conditions at once - prolonged droughts and heavy rainfall or flooding, which can endanger both human lives and infrastructure.
Food insecurity: Both drought and heavy rainfall lead to harvest loss in the affected areas. As a result of the weather changes, there is a risk of food insecurity in many affected countries. This in turn also has an impact on distant regions. Rising food prices as a result of food shortages make it difficult for many people to access food, even in countries not directly affected.
Health risks: The climate changes caused by El Niño – above all the increased humidity in some areas – can promote the occurrence and spread of diseases such as malaria, dengue fever and cholera. Floods and droughts also create conditions that negatively affect water quality and worsen people's living conditions.
Forest fires: In regions suffering from drought due to El Niño, the risk of forest and bush fires increases, which not only cause significant ecological damage, but also result in material losses for many people.

El Niño and climate change

While El Niño itself is a natural climate phenomenon that has been occurring for centuries, ongoing climate change is intensifying its effects. The higher temperatures resulting from man-made climate change lead to even more extreme periods of drought and heatwaves during an El Niño phase. Scientists also fear that El Niño and La Niña phenomena will become more frequent due to climate change.

Anticipatory humanitarian action and emergency relief: our response to El Niño events

DRR — Archive: Guilhem Alandry/Malteser International

Anticipatory Humanitarian Action is playing an increasingly important role for humanitarian actors and governments of affected countries. It enables them to prepare people for the damaging effects of the El Niño event in the best possible way or even to mitigate or avert them. By using early warning systems based on predictive data and forecasts, the population can react to impending disasters at an early stage. This forward-looking approach makes it possible to prevent or at least reduce the negative impact of El Niño on the lives and livelihoods of the people affected – even before the disaster reaches its full extent.

Malteser International's anticipatory aid approach focuses not only on immediate emergency relief and life-saving early warning, but also on strengthening the resilience of the local community. Through rapid response and recovery measures, including the implementation of contingency plans, we can make an important contribution to minimizing the impact of El Niño and similar events.

Donate now for our humanitarian aid!

"Anticipatory Action": A feasibility study for MI

In 2023, we started an exploration into Anticipatory Action, commissioning the Global Public Policy Institute (GPPi) to conduct a study to determine the feasibility of integrating Anticipatory Action into our humanitarian work. Anticipatory Action refers to proactive measures taken in anticipation of crises or disasters, aiming to reduce risks, mitigate impacts, and enhance resilience before the event occurs. This approach involves early warning systems, preparedness activities, and direct interventions aimed at addressing vulnerabilities and strengthening community capacities to cope with upcoming emergencies and future challenges.