Sea surface temperatures in the Pacific Ocean can affect the global climate through El Niño and La Niña. Luke Bender, Unsplash

El Niño: The climate wake-up call we need?

The climate cycle that could push us past 1.5 degrees

El Niño has officially begun. It’s projected to affect weather patterns around the world, break temperature records and – perhaps most alarmingly – tip us over 1.5 degrees Celsius global warming, if only temporarily.

The next few years could be a window into what a warmer world will look like, but will it be the wake-up call we need?

A visualization of global sea surface temperature anomalies between 1982 and 2017. NASA

What is El Niño?

El Niño is an irregular climate phenomenon where sea surface temperatures in the equatorial Pacific Ocean are warmer than average for several months. At the same time, low-level easterly winds that blow along the equator are weakened or even reversed. This leads to changes in global weather patterns, with much higher rainfall in some regions, severe droughts in others and a rise in average global temperature.

El Niño is the warm phase of a cycle known as the El Niño–Southern Oscillation (ENSO). The cold phase, known as La Niña, sees cooler-than-average sea surface temperatures in the tropical eastern Pacific.

This year, the cycle is moving from a three-year La Niña straight into an El Niño. Almost half of all years, however, fall into the neutral phase of the cycle, when temperatures don’t significantly deviate from the long-term average.

The strength of an El Niño event is determined by how much above average Pacific sea surface temperatures are, with higher temperatures often leading to much more severe weather events around the world. As of last week, there is a 56-percent chance this event will become strong at its peak.

Where does the name “El Niño” come from?

It is thought that El Niño (Little Boy) is a shortening of El Niño de Navidad (Little Boy of Christmas), a name given to the phenomenon by South American fishermen who, several centuries ago, noticed the sea warming some years during December, close to Christmas.

What effects does El Niño have?

El Niño has the most direct impacts on life in the equatorial Pacific, but regions around the world see their weather patterns changed in different ways. South America and the southern U.S. are likely to experience heavier than normal rainfall, while Australia and Southeast Asia can face hotter, drier weather with the potential for weaker monsoon rains in India.

Impacts in Europe are less clear cut, with many factors overshadowing the effects of El Niño, but shifts in temperature and precipitation are still routinely attributed to the ENSO cycle.

These global changes in weather have direct impacts, such as flooding and droughts, but also numerous secondary effects that can be equally damaging. The El Niño event in 1997–98, for example, led to what is considered the first global coral bleaching event, while the El Niño event of 2015 prolonged what was the longest global coral die-off on record.

El Niño has also been linked to regional disease outbreaks around the world, including cholera, Zika, dengue fever, and plague. This is due to ENSO-driven weather patterns altering the habitat of disease vectors, like mosquitoes, and creating conditions for the spread of waterborne diseases when, for example, floodwater overwhelms sewage infrastructure and contaminates drinking water.

Agriculture can also be severely impacted. Winter crop production in Australia, the world’s second-largest wheat exporter, is forecast to fall this year due to low rainfall driven by El Niño, while Thailand, Indonesia and Malaysia are expected to see rice production drop in the face of extreme heat and drought.

El Niño is expected to cause drought across Australia and Southeast Asia. Upesh Manoush, Unsplash

At a time when food prices and hunger levels are already high, a decrease in the supply of these staple crops could lead to greater food insecurity for those most vulnerable.

Cash crops, such as robusta coffee in Vietnam and Brazil, are also predicted to suffer from the changing weather patterns of this El Niño event, with even small shifts greatly impacting producers who rely on these crops for their livelihoods.

The financial repercussions of El Niño go far further than individual producers, however. This recent study predicted that an average event could cost the global economy USD 3.4 trillion, based on the costs of previous El Niño events.

El Niño can also have a dramatic effect on atmospheric carbon dioxide levels and thus longer-term global warming. Both flooding, as is likely in South America, and droughts, in places such as Indonesia, can prevent plants from photosynthesizing to their maximum capacity, reducing their absorption of carbon dioxide from the atmosphere. Meanwhile, additional carbon is released into the atmosphere by widespread plant death and wildfires caused by extreme temperatures.

The strong El Niño event of 2015, for example, led to one of Indonesia’s most severe fire seasons on record, with forest and peatland fires releasing more carbon dioxide per day than the entire EU.

Singapore haze
A thick haze in Singapore caused by wildfires in neighboring Indonesia in 2015. Charles EYES PiX, Flickr

“In 2015, we went out to the field and measured the emissions from forest and peatland fires,” explains Daniel Murdiyarso, a principal scientist with CIFOR-ICRAF and a forest meteorologist who researched fire carbon emissions over maritime southeast Asia at the time.

“During those two months, the average or daily emissions of carbon dioxide equivalent was about 11.3 teragrams,” he added.

“So, while the effects of El Niño is not direct to climate change, if it is causing the burning of biomass, it will certainly impact climate change because the increase in greenhouse gas loading is so dramatic.”

What makes this El Niño event different?

That said, ENSO has been cycling through its phases for thousands of years. So, what makes this event any different?

Simply put: human-made climate change.

“When you look at the background warming we’ve got, largely from anthropogenic sources – land use change, burning fossil fuels, concrete, that are bringing a steady rise in the concentration of greenhouse gases – in El Niño years, because we have additional warmth, we’re likely to get a spike in global average temperature,” explains Grahame Madge, spokesman for the U.K.’s Met Office.

The higher that temperature is, the “greater potential for extreme weather events, whether heatwaves or precipitation as well as patterns that could result in more drought.”

Coal mining
Despite the climate emergency, coal remains a major source of energy globally. Artyom Korshunov, Unsplash

And it’s those anthropogenic sources that are the main issue. Without our contribution, ENSO couldn’t bring us anywhere near the 1.5-degree threshold that the World Meteorological Organization (WMO) now predicts we will exceed for at least one year between 2023 and 2027.

“In 2021, the increase in temperature from the pre-industrial period was already 1.1 degrees,” says Murdiyarso. “So, let’s not divert people’s attention from our failure to reduce emissions from fossil burning; let’s not send a message that El Niño is the only cause.”

“One has to remember that the burning of fossil fuels continues or is even increasing. With economic turmoil, European countries are starting to use coal again. After Fukushima, Japan is using coal again.”

In fact, global temperatures have increased so significantly due to greenhouse gas emissions that today’s La Niña events – the cooler phase of the cycle – are now warmer than the El Niño of 1998, says Madge.

It’s no surprise, then, that this El Niño event is expected to “combine with human-induced climate change to push global temperatures into uncharted territory,” as WMO Secretary-General Petteri Taalas put it in a recent statement – with “far-reaching repercussions for health, food security, water management and the environment.”

Fortunately, we won’t be experiencing the most severe effects of the climate crisis until we’ve crossed the 1.5-degree mark in the long run, rather than temporarily as predicted in the next four years.

But the fact that we’ve reached this point should act as a stark warning, says Madge: “The headroom is getting less and less as we go forward, which provides less room for mitigation.”




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