New Scientist
The world’s most powerful El Niño is unleashing extreme heat, devastating droughts, wildfires and floods across the globe.
El Niño heralds a tumultuous year
Author: Michael Le Page
THE world faces a difficult period ahead, as the El Niño weather phenomenon looks set to wreak havoc.
Already, India is grappling with the impacts of one of the driest monsoon seasons on record. Meanwhile, in Indonesia, schools have closed and authorities have advised residents to stay indoors to avoid the toxic smoke from huge wildfires supercharged by El Niño. Hundreds of thousands of people have faced respiratory illness, and carbon emissions are on track to equal Indonesia’s catastrophic 2015 fires.
In this eight-page special report, we take a look at what this means for the world – from how the next few months could play out (see below) to its impact on food security (see page 8) and how it will end (see page 11).
We will also look at how the worst El Niño in history prepared us for this supercharged event (see page 6) and at some of the more ambitious ideas to mitigate its impacts (see page 10). But first, how did this El Niño grow so much bigger than usual, and what will its long-term effects on the planet be?
MIND-BLOWING. Unprecedented. Off the charts. Godzilla-level. Superlatives have been flying about the current El Niño climate pattern, which is already the strongest on record months before it is expected to peak – and unusually, they are coming from scientists, rather than the media. So, what has made this such an exceptional event? And for how long will we feel its effects?
To understand this El Niño, we have to understand La Niñas, the opposite phase of the climate pattern. During La Niñas, trade winds blow west across the equatorial Pacific, pushing surface waters warmed by the sun towards Australia and Indonesia. This piles up a layer of water known as the “warm pool”. And it really does pile up: sea level in the western Pacific rises by as much as 20 centimetres.
It gives us a glimpse of what is coming if we continue to warm the planet with carbon
The bigger the warm pool gets, the more unstable it becomes. If the trade winds holding it in place weaken or reverse direction, the warm water spills back across the Pacific, making surface waters along the equator abnormally warm – an El Niño event. So the extent to which an El Niño raises global temperatures and causes extreme weather depends on how big and hot the warm pool gets, and on how much of it moves east across the Pacific.
By late 2025, the heat content of the western Pacific was much higher than normal – although it wasn’t the highest on record. “Based on that alone, one might not have expected this event to become as strong as it has,” says Michael McPhaden at the US National Oceanic and Atmospheric Administration.
The second key factor was a series of strong bursts of wind blowing east, pushing the extra-hot warm pool towards South America. This isn’t just a surface phenomenon, says McPhaden. Each wind burst creates a downward bulge in the layer of warm water, known as a Kelvin wave, which travels across the Pacific over the following six to eight weeks.
Every Kelvin wave increases the thickness of the warm layer in the eastern Pacific. Put another way, the bottom of the warm layer, or thermocline, becomes deeper. “The thermocline is currently more than 80 metres deeper than normal in some areas,” says McPhaden.
The deeper the thermocline, the harder it is for colder water to well up and reach the surface. So we now have a huge amount of extra warm water spreading across the surface of the Pacific and transferring huge quantities of heat to the atmosphere, with repercussions across the globe.
The question of whether global warming is making El Niños stronger is unresolved, says Michael Mann at the University of Pennsylvania. “It’s honestly an open question from my stance.”
The number of observed El Niño and La Niña events in modern times is too small to reveal any link. A recent study of corals in the Galapagos suggests there is a link, but Mann says there are crucial gaps in the coral record that mean no firm conclusion can be drawn.
Climate models are little help either, he says. “The models [are] nearly equally split as to whether the amplitude of El Niño events is likely to increase or decrease with anthropogenic warming.” What is clear is that warming amplifies the damage done by El Niños.
The current super El Niño will also lead to a big spike in global warming, says Mann. “It gives us a glimpse of what is coming down the pike if we continue to warm the planet with carbon pollution. Warmer oceans, more evaporation, bigger flooding events, hotter continents and worse droughts leading to more extensive and destructive wildfires.”
Once this monster El Niño ends (see page 11), its effects will continue to be felt. “I expect that this super El Niño event will drive multiple climate-regime shifts like we’ve seen after past super El Niño events,” says hurricane specialist Jeff Masters. “Regime shifts tend to cause considerable trouble – significant disruptions to ecosystems and to the humans that depend on them.”
For instance, this El Niño is expected to lead to a devastating drought in the Amazon that could kill off some of the remaining areas of rainforest. This would release huge quantities of carbon dioxide and also make the whole region permanently drier, because much of the rainfall in rainforests comes from the water evaporating from trees.
This super El Niño event will drive multiple climate-regime shifts like we’ve seen after past ones
Some effects will be temporary. For instance, the Indian Ocean can become warmer after El Niños – on top of the warming due to global heating – leading to floods in some nearby regions. Some of the worst floods in the Yangtze river occurred in the summer of 1998, after the El Niño that ended in May.
The biggest concern is that the current El Niño could lead to changes that last decades or more. Last year, Jong-Seong Kug at Seoul National University in South Korea and his colleagues published a study showing that the combination of extreme El Niños and global warming can produce climate-regime shifts.
After the 2015 super El Niño, there was a sudden increase in sea-surface temperatures in the Gulf of Mexico that has persisted ever since. The El Niño wasn’t the only factor involved, says Kug, but it contributed to this jump.
The even-stronger El Niño now under way is more likely to trigger such shifts. “We are experiencing a very strong El Niño event,” says Kug. “Based on our study, such an extreme event could substantially increase the likelihood that various components of the Earth system are pushed toward, or even across, regime-shift thresholds.”
In other words, in some parts of the world, the climate will never go back to how it was. “Our civilisation is adapted to the climate of the 20th century, and it is costly and disruptive to be forced to deal with sudden climate regime-shifts,” says Masters.
Credits: TCA, LLC.