A Pacific phenomenon and an ocean already breaking records - critical summary review

El Niño is a natural phenomenon that begins in the Pacific Ocean and ends up moving rainfall, temperatures and storms thousands of kilometres away. It can reach the supermarket shelf, the harvest, the ports and decisions taken by governments on the other side of the world — and the one forming now is being described by Britain's national weather service as unprecedented.

How El Niño works

El Niño returns every two to seven years and lasts around a year. The trade winds that normally blow east to west across the Pacific weaken, or even reverse, and the warm water they usually pile up in the west spreads eastward and reaches the surface. The heat escaping from ocean into atmosphere lifts global temperatures and rearranges where rain falls. Scientists declare an El Niño when sea surface temperatures in a reference patch of the Pacific sit at least half a degree above average.

The consequences are not the same everywhere. Some regions turn hotter and drier, others wetter and cooler. Typically that means drought and wildfire risk in Australia and the Amazon, a higher chance of flooding in Peru, Ecuador and the southern United States, and — counterintuitively — fewer Atlantic hurricanes, because the pattern strengthens the upper-level winds that tear storms apart. Michelle L'Heureux, of the US National Oceanic and Atmospheric Administration's climate prediction centre, stresses that a stronger event raises the odds of these outcomes without guaranteeing any of them.

That is the backdrop against which this month's news arrives.

The record that came in the wrong month

The average temperature of the world's seas outside the polar regions reached 21.1C in August, narrowly past the previous record set in March 2024, according to the European Union's Copernicus climate change service.

What unsettles scientists is less the margin than the calendar. Ocean temperatures normally peak in March and April, at the end of the southern hemisphere summer, because the south holds more of the planet's ocean surface. This time the record fell in August — while the developing El Niño is still well short of its expected peak, which forecasters place somewhere between November and January.

"This record is another clear signal of an ocean under growing stress," said Samantha Burgess, of Copernicus. "El Niño is adding heat to the system, but it is doing so on top of decades of human-driven warming."

Warmer seas feed storms extra moisture and energy, raise sea levels through thermal expansion, blunt the ocean's ability to absorb carbon dioxide and drive marine heatwaves that damage coral reefs and seagrass. Boris Worm, a biology professor at Dalhousie University in Canada, put the timing this way: "The thing that makes my heart sink is that this starts so early and it's so out-of-normal that you know when it hits its peak, it's going to be unprecedented." He and other researchers warn about the Peruvian anchovy fishery, the largest in the world, which usually collapses during El Niño years and underpins a food chain of larger fish, seabirds and people.

Why forecasters call it unprecedented

A typical El Niño lifts Pacific sea temperatures by rather more than a degree. The Met Office, the United Kingdom's weather service, expects this one to exceed three degrees, which it says would make it the largest since the nineteenth century.

"We should be clear that this is an unprecedented event," said Adam Scaife, its head of long-range forecasting. "I have never seen an El Niño signal this intense in our forecasts." Nothing that strong appears in the modern record, which begins in 1950. NOAA, using a new tracking index, puts the probability that this becomes the most intense event of that whole series at 69%.

The second consequence is global temperature. Because most of the heat is released to the atmosphere in the year after the event's winter peak, Met Office scientist Nick Dunstone says 2027 is very likely to replace 2024 as the warmest year on record.

From the Panama Canal to the checkout

The Panama Canal handles about 5% of global maritime trade, and it runs on rainwater: its locks are fed by freshwater lakes that a drought drains. With the wet season running drier than usual, the Panama Canal Authority reversed course and announced daily transit caps, cutting crossings twice in September, down to 32 ships a day by mid-month.

The pressure was already visible. In early August, dozens of vessels waited their turn at the Pacific end, some for more than a week; one container ship paid $4 million to fast-track its trip. Ships must also sit higher in the water, which means carrying less cargo per voyage. Shipping company MSC has raised its canal surcharge, and some importers are rerouting to Californian ports and trucking cargo across the United States — which tightens land transport and lifts prices even for goods that never went near the canal. Experts interviewed by CNN say the cost lands on consumers, from electronics to the ingredients used to make common medicines.

Governments in the region have moved from forecast to decree. Panama and El Salvador declared emergencies over drought; El Salvador's civil protection agency announced a red alert for meteorological and farming drought across the country, and its agriculture ministry began distributing food to rural families without irrigation. Honduras placed most of its territory on drought alert. Peru declared a state of emergency in a third of its cities. The United Nations warned in early August that conditions created by El Niño could push 50 million people into acute hunger by the end of next year.

Brazil split in two

In Brazil the pattern points in opposite directions. Diogo Arsego, a meteorologist at CPTEC, the government's weather and climate research centre, says the event took shape in June, should remain active into early 2027 and peak between October and November.

The North and Northeast face less rain, falling river levels, pressure on water supply and a higher fire risk. In the Centre-West, heat and low humidity favour fires, especially in the Pantanal wetlands. The Southeast can expect heat and irregular rainfall. The South gets the reverse: persistent storms, flooding and landslides. The Brazilian Association of Municipalities has published a guide urging city halls to map risk areas, update contingency plans and prepare shelters and emergency contracting paperwork in advance.

The economic reading is already being made. A study reported by G1 estimates that in a strong El Niño, fresh food prices — meat, vegetables — could rise close to 20%, with the heaviest effect appearing roughly half a year after the climate shock. The credit firm Multiplike calculates that a very strong event could cut Brazilian grain output by up to 10%, which would change when and how much raw material reaches processors and squeeze their working capital. Strategists at large banks, according to Valor, are pointing to energy, agribusiness and retail as the most exposed sectors, while noting that few share prices reflect the scenario yet.

Beyond the Pacific

In the United States, El Niño tends to push the jet stream south, bringing wetter, cooler weather to southern states and warmer, drier conditions to the north. California is expected to be the epicentre: scientists say extensive coastal flooding is close to certain, and Patrick Barnard, of the University of California, Santa Cruz, estimates the extra coastal water this event will add would put an additional $60 billion in property at risk compared with a normal year.

In the United Kingdom, the Met Office expects a wetter, stormier autumn and early winter, arriving after a summer of heatwaves and drought across England and Wales. And Hawaii, normally shielded by cooler surrounding water, has been brushed by two intensifying tropical storms in as many weeks; the first, Hurricane Lala, triggered landslides and flash flooding, and one death was blamed on it.

What to do with this information

Three markers will tell you, in the coming months, whether the more extreme scenarios are materialising — and none requires specialist knowledge to follow.

The first is the monthly intensity updates from NOAA and the Met Office. The peak is expected between October and January, depending on the forecaster; the size of the anomaly they report is what separates a strong event from a historic one, and everything downstream scales with it.

The second is the Panama Canal. The traffic and draft limits taking effect in September are the visible part of the shipping cost chain, and further tightening would show up later in the price of imported goods — electronics, medicines, industrial inputs — as well as in freight rerouted to other ports.

The third is domestic: grain harvest reports for soybeans and maize, and the fresh food component of Brazil's consumer price index. That is where a strong El Niño would register first in a household budget, and economists say the effect tends to appear months after the weather shock, not during it. If you are planning spending, or run a business tied to agriculture or logistics, those are the two quarters to watch.