Revolution, ruin … and vanishing anchovies: El Niño is coming and it’s making experts nervous

An area is uncovered by the lowering of the water level from the Magdalena river, the longest and most important river in Colombia, due to the lack of rain, in the city of Honda
The climatic impacts of El Niño are felt over many months – and even years – across the planet - John Vizcaino/REUTERS

What links poor European crop yields in the late 1700s (the spark that helped light the French Revolution), a deadly famine in 1876 which killed 13 million people in north China, and the sudden disappearance of thousands of anchovies from Peruvian waters in 1972?

No, the answer is not Marty McFly or Doctor Who, but rather a global weather pattern that, for millennia, has subtly shaped and defined the long arc of human history.

Occuring every three to seven years, an El Niño describes the unusual warming of the eastern Pacific Ocean, just off the coast from Peru. The phenomenon is declared when sea temperatures in the region rise 0.5 °C above the long-term average.

This subsequently drives surface air temperatures and pressure changes throughout the equator, which then go on to affect seasonal weather over both hemispheres.

The event is driven by slow, natural fluctuations in ocean currents and wind patterns, but the climatic impacts are felt over many months – and even years – across the planet.

A vendor selling ice cream waits for customers at the Galle Face Beach in Colombo
The phenomenon affects seasonal weather over both hemispheres - ISHARA S. KODIKARA/AFP via Getty Images

The fallout includes: increased global temperatures; heightened rainfall; intense flooding and droughts; surges in infectious diseases, including malaria and even plague; forest fires; mass fish die-offs. The list goes on.

On the upside, an El Niño normally results in fewer hurricanes in the Atlantic and can help ease drought in dry parts of the world.

This “shock to the system,” as described by Dr Madeleine Thomson, Head of  Climate Impacts and Adaptation at Wellcome, is once again looming on the horizon, with an El Niño expected to come into effect over the coming months.

Climate scientists have predicted there is a 90 per cent chance that the phenomenon will take hold in the latter half of the year. Its impacts are unlikely to be felt until the end of the year, but there is concern it could be a strong one.

“The distinct El Niño warming pattern, caused by slow, natural fluctuations in ocean currents and heat, is beginning to emerge in 2023,” says Professor Richard Allan, from the National Centre for Earth Observation at the University of Reading.

“It’s too early to say how the current El Niño storyline will unfold, but if it does unleash its full power in 2024 then it’s very likely that yet another record global temperature will be breached.”

People walk through a dust storm on a hot summer day in Prayagraj
A country’s experience of El Niño varies from region to region and season to season - SANJAY KANOJIA/AFP

A country’s experience of El Niño varies from region to region and season to season, and is dependent on the intensity of the phenomenon when it comes to pass.

In parts of the world, like the baked, semi-arid mid-west of the US, an El Niño can bring increased rainfall during the summer months. Conversely, it can drive unusually warm temperatures and dry conditions in regions of Africa that are normally very wet.

“It doesn’t all happen the same way around the world,” says Dr Thomson. “The effects are also seasonal. So, for example, the impact on the rain is going to happen during a country’s rainy season.”

Despite the uniqueness of each El Niño, there are some constants: the most acute effects are felt within the tropics; the global temperature will rise (by how much is dependent on the El Niño strength); and historically, the event is associated with droughts in Indonesia, Malaysia, and the Philippines, while Peru and Kenya suffer from heavy rainfall.

The phenomenon is the warm phase of the El Niño Southern Oscillation (ENSO), which describes the periodic variation in winds and sea surface temperatures over the eastern Pacific Ocean.

Buddhist nuns collect alms with their head covered with towels and under umbrellas to shelter from the sun during a heatwave in Yangon
Some of the worst climate-related crises in recent memory have been linked to the phenomenon - SAI AUNG MAIN/AFP via Getty Images

The cool phase of the ENSO is known as La Niña, which has been in place for the last three years and acted as a temporary brake – albeit not a very good one – on rising global temperatures; indeed, the last eight years have been among the warmest on record.

But it is El Niño which is the more sinister sibling out of the two. Some of the worst climate-related crises in recent memory have been linked to the phenomenon.

In 2015/16, a strong El Niño year, Ethiopia suffered catastrophic drought, in which 10 million people were affected. Before then, the 1997-98 El Niño episode caused up to £77 billion in global damages. Notably, the event drove extreme rainfall in Kenya and led to a severe outbreak of Rift Valley fever, killing more than 400 people.

Along with flooding and food insecurity linked to droughts, infectious disease outbreaks are another significant fallout of an intense El Niño. “There’s lots of different ways that El Niño will drive the climate and change the average distribution of disease and make it more extreme,” says Dr Thomson.

She points to the example of plague and leptospirosis, two diseases carried by rats.

“When you get massive flooding, rats move to higher ground so they move into villages,” says Dr Thomson. “So you suddenly get this interaction with humans that wasn’t there in the past. And you get explosions of plague and leptospirosis.”

Any infection that is animal or water borne – from malaria to cholera – will typically increase in prevalence during a strong El Niño that triggers flooding and natural disaster.

A Ministry of Health worker fumigates against the dengue virus in the San Juan de Lurigancho neighborhood of Lima, Peru
Infectious disease outbreaks are another significant fallout of an intense El Niño - Sebastian Castaneda/Bloomberg

It was anchovy fishermen in Peru who first noticed and named El Niño events in the tropical Pacific hundreds of years ago. Their catches would fluctuate and the largest declines were seen near Christmas when the ocean was at its warmest – they called it El Niño de Navidad, the boy of Christmas.

In the 1960s and early 1970s, Peru was the biggest fishing nation in the world. In 1970, Peruvian fishermen caught nearly 10 million metric tons of anchovies. In 1971, they caught even more. Then, the following year, there were no anchovies to be found.

Having already suffered from overfishing during the previous decade, the arrival of El Niño in 1972, and the warm waters it brought, meant there was less food for the anchovies to survive, resulting in a sudden wipe out of stocks. Anchovy numbers off the coast of Peru haven’t recovered since.

Yet it’s not all doom and gloom when it comes to El Niño. There are some benefits to the phenomenon.

After a La Nina episode, which is “basically an intensification of the normal climate,” says Dr Thomson, a moderate El Niño can bring “relief” to dry or wet countries in the form of rainfall and warm temperatures, respectively. “You get the opposite [weather] coming in with an El Niño.”

That means for farmers who are battling drought, an El Niño can ease water shortages and insecurity.

And because of the way the phenomenon “interacts with the global weather patterns,” says Dr Liz Stephens, Associate Professor in Climate Risks and Resilience at the University of Reading, “we’d actually expect fewer hurricanes in the Atlantic affecting the Caribbean and the US.”

“There can be winners or losers,” adds Dr Thomson.

A dead fish lies on a dried up section of Osman Sagar lake on the outskirts of Hyderabad, India
Climate change is exacerbating the effects of El Niño - Mahesh Kumar A/AP

In the months ahead, scientific consensus on the intensity of the looming El Niño will further strengthen as the ‘spring predictability barrier,’ as it’s known, is breached.

“There’s a really high degree of uncertainty in an El Nino prediction before June. This uncertainty reduces dramatically once you’ve passed through this spring barrier. And it is because you’re going through a transition season,” says Dr Thomson

One growing certainty, however, is that climate change is exacerbating the effects of El Niño, as any spike in global temperature driven by the phenomenon is set against an already elevated starting base.

“There is evidence that climate change is making El Niño events more extreme and will likely do so in the future, and therefore impacts from these events will be more extreme,” says Dr Melissa Lazenby, a lecturer in Climate Change at the University of Sussex.

How exactly these impacts materialise remains to be seen – but there’s no doubt that the El Niño phenomenon will continue to make its presence felt in a myriad of ways, whether it’s fuelling revolution and ruin or guaranteeing hurricane-free holidays in the Caribbean.

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