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Why can an anomaly that originates in the tropical Pacific affect the global climate? What is its relationship with climate change, and what does it mean for Europe and Sardinia? El Niño is one of the most important natural climate phenomena on Earth. Although it originates in the tropical Pacific Ocean, it can influence weather and climate on a global scale by altering temperatures, precipitation patterns, and extreme weather events through complex interactions between the ocean and the atmosphere. Understanding how it works is essential for interpreting climate change dynamics and assessing its potential impacts on the Mediterranean region.

When the Pacific Speaks to the Rest of the World

Every so often, the planet seems to change its rhythm. Rainfall patterns shift, global temperatures rise, some regions experience devastating floods while others face prolonged droughts. Behind many of these changes lies a climate phenomenon that develops more than 15,000 kilometers from the Mediterranean: El Niño.

For decades, it was regarded primarily as a problem affecting fishermen along the Peruvian coast. Today, we know it is one of the Earth's most powerful natural climate regulators, capable of influencing agriculture, water availability, marine ecosystems, and the frequency of extreme weather events across the globe.

Understanding El Niño means understanding how the Earth's climate system works—and why climate change is making its impacts increasingly difficult to predict.

What Is El Niño and How Does It Work?

El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO), a coupled ocean-atmosphere system affecting the equatorial Pacific.

Under normal conditions:

• Trade winds blow from east to west.
• Warm surface waters accumulate near Indonesia and Australia.
• Along the west coast of South America, cold, nutrient-rich deep waters rise to the surface through upwelling.

During an El Niño event, this pattern changes:

• The trade winds weaken.
• Warm water that has accumulated in the western Pacific shifts toward the central and eastern Pacific.
• The atmosphere responds by altering large-scale patterns of rainfall and temperature.

The name "El Niño" was coined by Peruvian fishermen, who noticed the phenomenon around Christmas and named it after the Christ Child.

A Phenomenon Without a Clock

One of the most fascinating characteristics of El Niño is that it does not follow a regular schedule. It does not occur every five or ten years. Scientific literature indicates an average recurrence interval of between two and seven years, but actual intervals can vary considerably.

This is because ENSO results from a complex interaction among:

• tropical winds;
• ocean currents;
• internal ocean waves;
• atmospheric pressure differences;
• the storage and release of thermal energy.

Scientists describe ENSO as a quasi-periodic and partly chaotic system. It naturally oscillates between El Niño, La Niña, and neutral conditions, but it is impossible to predict years in advance exactly when the next event will begin.

A Century of El Niño: The Strongest Events

Looking back over the past century reveals an irregular sequence of El Niño episodes.

Event	Intensity
1957–58	Strong
1965–66	Moderate to Strong
1972–73	Strong
1982–83	Very Strong
1986–87	Moderate to Strong
1991–92	Moderate
1997–98	Very Strong
2002–03	Moderate
2009–10	Strong
2015–16	Very Strong
2023–24	Strong

The three strongest modern El Niño events are generally considered to be:

• 1982–83
• 1997–98
• 2015–16

Many climatologists also regard the 2023–24 event as one of the most significant of the past two decades.

La Niña: El Niño's Less Famous Sister

If El Niño represents the warm phase of ENSO, La Niña is its opposite.

During La Niña:

• Trade winds strengthen.
• Warm water accumulates even more toward Australia and Indonesia.
• Cold-water upwelling intensifies along the South American coast.
• The eastern Pacific becomes cooler than average.

La Niña also influences the global climate, often in ways opposite to El Niño:

• Increased rainfall in Australia.
• Drier conditions across parts of South America.
• Different patterns of tropical cyclone activity.
• Variations in global temperatures.

etween 2020 and 2023, the planet experienced a rare triple-dip La Niña, with three consecutive La Niña years—an event observed only a few times over the past seventy years.

Importantly, La Niña does not offset climate change. Even during recent La Niña years, global average temperatures remained among the highest ever recorded.

El Niño and Climate Change: What Is the Connection?

This is probably the most important question.

The scientifically accurate answer is more nuanced than it is often portrayed.

What we know with certainty is that El Niño has existed for thousands of years. It was not created by human activities or by global warming.

What we still do not know is whether climate change is increasing the total number of El Niño events. The natural variability of the ENSO system is so large that it remains difficult to distinguish a possible human influence from the system's inherent variability.

Many climate models suggest that a warmer ocean could favor stronger ENSO events or alter their characteristics compared with the past.

Even if El Niño itself did not change, its impacts today would likely be stronger because:

• the oceans are warmer;
• the atmosphere contains more energy;
• the atmosphere holds more water vapor.

As a result, when a strong El Niño occurs, it acts upon a climate system that has already been altered by anthropogenic global warming.

Global Climate Impacts

El Niño alters the position of major tropical convection zones and atmospheric circulation patterns.

Its best-known impacts include:

Heavy Rainfall and Flooding

• Peru
• Ecuador
• Western California

Drought

• Australia
• Indonesia
• Southern Africa

Marine Ecosystems

• Temporary declines in fishery productivity.
• Coral bleaching.
• Disruptions to marine food webs.

Global Temperatures

Many of the warmest years on record have coincided with particularly strong El Niño events.

Does El Niño Affect the Mediterranean?

This is the question of greatest interest for European readers.

The answer is yes—but much less directly than in tropical regions.

Scientists describe this relationship as a teleconnection, meaning a long-distance climatic linkage. However, the ENSO signal over Europe is relatively weak and is often masked by atmospheric variability over the North Atlantic, particularly the North Atlantic Oscillation (NAO).

 

For this reason, it is incorrect to say, "There is an El Niño, therefore this will happen in Sardinia."

A more accurate statement is:

"El Niño changes the probability of certain atmospheric circulation patterns that may also influence the Mediterranean."

Possible Impacts on Sardinia

Sardinia lies within what scientific literature identifies as the Mediterranean climate hotspot.

Over recent decades, the island has experienced:

• rising average temperatures;
• more frequent heatwaves;
• increasingly intense rainfall events;
• growing water stress.

Within this context, a strong El Niño may act as an additional factor amplifying climate risks.

Possible indirect effects include:

• longer summers;
• increased evaporation;
• reduced water availability;
• higher wildfire risk;
• more frequent marine heatwaves;
• less frequent but more intense rainfall.

Naturally, none of these impacts can be attributed solely to El Niño, but the phenomenon may contribute to shaping the broader climatic conditions in which they occur.

Looking Ahead

In June 2026, the World Meteorological Organization (WMO) indicated a high probability that a new El Niño episode could develop in the following months. Forecasts suggested the possibility of a strong event with significant global impacts.

This does not mean climate disasters will automatically occur. Rather, it highlights that the Earth's climate continues to be shaped by the interaction between natural climate variability and human-induced climate change.

Conclusions

El Niño is one of the clearest demonstrations of the interconnected nature of the Earth's climate system.

It originates in the tropical Pacific, yet it can influence weather and climate across distant continents. It is a natural, ancient, and irregular phenomenon that continues to challenge scientists' ability to forecast its evolution.

Today, the central question is not whether El Niño exists because of climate change—we know it does not.

The real question is:

To what extent is an increasingly warmer global ocean changing El Niño's behavior and amplifying its impacts?

Answering this question represents one of the major frontiers of modern climate science and one of the keys to understanding the future climate of the Mediterranean.

Selected References

• World Meteorological Organization – ENSO Overview 
• NOAA Climate.gov – ENSO Portal 
• NOAA NCEI – ENSO Monitoring 
• Benassi et al. (2021), El Niño teleconnection to the Euro-Mediterranean late winter climate. 
• Rodríguez-Fonseca et al. (2016), A Review of ENSO Influence on the North Atlantic. 
• IPCC AR5, Chapter 14 – Climate Phenomena and their Relevance for Future Climate Change. 
• MedECC (2020), Changes in the Future Summer Mediterranean Climate.

article by: Alessio Satta