A super El Niño that is gathering strength in the Pacific Ocean may have been made worse by climate change, according to new analysis of coral records that suggest El Niños have become more intense as global temperatures have climbed.

The impacts of El Niño – droughts, floods and storms – are already exacerbated by rising global temperatures, because a warmer atmosphere intensifies both rainfall and droughts.

But scientists have long struggled to untangle the effect of climate change on the El Niño Southern Oscillation (ENSO) cycle, which drives El Niño events. Part of the difficulty is that detailed observational records only began in the 1980s. A much longer timescale than that is needed to tease out a trend from natural variability.

at the University of Michigan and her colleagues hope corals can provide the answer. They collected living and dead corals from around the Galapagos Islands in the eastern Pacific ocean, where El Niños first develop.

They used uranium and thorium dating to identify the age of the corals, then analysed the chemistry of their skeletons to track changes to sea temperatures during their lifetime. In that way, they built a time series of sea surface temperatures in the eastern Pacific spanning the past 1000 years.

El Niño and La Niña events are measured by changes to sea surface temperatures in the Pacific, so by building this time series, Cole and her colleagues could track the fluctuating ENSO cycle through the centuries.

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“The chemistry of the coral skeleton preserves a record of the environment in which it grew, and certain aspects of the chemistry are especially sensitive to temperature changes,” says Cole.

The team found that, over the past 40 years, variability in the ENSO cycle has increased by 36.5 per cent compared with the pre-industrial period. This increase in variability has been driven largely by more intense El Niño events, the analysis found.

The corals collected by the team covered about half the 1000-year time period. Nevertheless, Cole is confident in the overall trend identified. “I think we show pretty clearly that the increase in variability in ENSO is tracking global temperature closely,” she says.

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The findings add to an that suggests the ENSO cycle is changing in response to rising temperatures. “The evidence is better than 50-50 that climate change is affecting El Niño,” says at Columbia University in New York, used tree ring data to identify an increase in El Niño activity in recent years.

Although the research does not include the recent El Niños in 2015, 2023 and 2026, Cole says they are consistent with the trend identified by the corals. When the current El Niño peaks at the end of this year, sea surface temperatures in the east-central Pacific Ocean are projected to reach 4°C above normal, a 60 per cent increase over the old record.

at the US National Oceanic and Atmospheric Administration (NOAA) agrees. “If the current El Niño turns out to be as strong as we expect, that past decade will have witnessed three major El Niños – a sequence not seen before in the instrumental record dating back to the late 19th century,” he says. “It will add to the mounting evidence that climate change is amplifying the ENSO cycle… which is a concern considering the far-reaching global impacts that ENSO has on humans and natural systems.”

Some 150,000 baby common octopuses (Octopus vulgaris) have just been released into the waters off Italy’s Adriatic coast in one of Europe’s first pilot experiments to test whether the species can help control the invasive blue crab (Callinectes sapidus), which eats native shellfish and threatens the fishing industry and marine ecosystems.

“The project is appropriate as a carefully controlled pilot experiment, but it is not yet a proven effective control strategy,” says , a marine ecologist at the Virginia Institute of Marine Science, who isn’t involved in the initiative.

Two years ago, �����Ի���, two aquaculture researchers at the University of Bologna, Italy, began to wonder whether octopuses offered a way to control blue crabs off the coast of Emilia-Romagna, a region of north-east Italy where damage caused by the blue crabs has cost the fishing industry £14.7 million since 2022. 

Previous studies had , backing up what local fishers had been seeing for a decade as populations of the Atlantic-native invasive species began to surge along Italian coasts.

However, octopuses tend to do better on rocky seabeds, while the Adriatic coast is rather sandy, which may help explain why octopus numbers there have been falling in recent decades. The regional government of Emilia-Romagna has installed artificial shelters for octopuses in an effort to reverse the decline. 

Under a research project co-financed by the regional government, Mordenti and Casalini caught eight common octopuses – four females and four males – from the Emilia-Romagna coast, transferred them to the laboratory and gave them about three months to acclimatise to their new surroundings. Their tanks were carefully monitored and maintained under conditions designed to simulate those at sea. “Not only did we find that the fishermen were right, but we also found that octopuses could consume up to four blue crabs a day,” says Mordenti.

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The researchers then arranged the octopuses into four breeding pairs and allowed them to mate and produce eggs. 

Earlier this week, the scientists released 150,000 millimetre-long, lab-raised larvae into the waters off the coastal towns of Cesenatico and Riccione. 

They estimate that only 1 per cent will survive to adulthood. After hatching, octopuses start their lives as tiny, free-floating larvae known as paralarvae. They drift through the water and may be eaten by fish. The hope is that a few will escape this fate and grow large enough to begin preying on blue crabs — a feat even small common octopuses weighing less than 800 grams are capable of, the researchers say.

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“Our aim was to bolster the population of a native species already found naturally in the Adriatic,” says Casalini. 

“We’ll work with fishermen to assess whether the releases will have had an effect by the end of the year,” says Mordenti. 

But some scientists argue that this strategy needs more study. “Blue crabs are extremely prolific and fast‑growing, and their preferred habitats often differ from those of octopuses,” says marine biologist  at the Institute of Marine Research, Spain. 

“Starting by releasing paralarvae as if they were wheat seeds scattered in the water seems like a rather simplistic approach,” says , a zoologist at the University of Naples Federico II, Italy. “A controlled environment is one thing; the open sea is a whole different ball game.”

The super El Niño climate phase that has begun in the Pacific Ocean is already the strongest on record on some measures. When it peaks at the end of this year, sea surface temperatures in the east-central Pacific Ocean are projected to reach 4°C above normal, a 60 per cent increase over the old record.   

As well as raising global temperatures, El Niño also shifts atmospheric circulation patterns, causing extreme weather around the world. This brings drought to some regions and flooding to others, damaging property and disrupting food supplies.

While the exact impacts vary from El Niño to El Niño, what’s clear is they will, on the whole, be stronger than in previous events.

“If you ramp up the size of your El Niño, you tend to ramp up the impacts in most regions of the world,” says Nick Dunstone at the UK Met Office, the national weather service. “It’s hard to know exactly which regions are going to be impacted the worst, but in general it’s fairly linear.”

El Niño forms when trade winds weaken, allowing water they have pushed into the “warm pool” in the western Pacific to run back eastward. This huge blob of warm water heats the atmosphere.

When El Niño isn’t occurring, the heat of the warm pool causes moist air to rise into the atmosphere above it, with the moisture condensing and falling as rain over South-East Asia. At the same time, air sinks over the cooler eastern Pacific. The warm air aloft, now mostly free of moisture, flows in to replace it, creating a giant loop. This loop is joined up with similar loops that circle the global tropics in what is known as the Walker circulation.

But when the warm pool sloshes eastward across the Pacific during El Niño, the centre of rising moist air moves with it, the entire Walker circulation eastward. As a result, the warm, dry air now sinks over South America rather than the eastern Pacific. Another loop of warm, dry air has also shifted and begun descending over South-East Asia and Australia. The Met Office is forecasting dry conditions in these areas over the next few months.

“The Amazon is a concern, as is Borneo and places in Indonesia and Australia as well,” says Dunstone. “Those are some of the regions that wildfire risk would be greatly increased.”

During the 1982-83 super El Niño, the “Great Fire of Borneo” 36,000 square kilometres of rainforest. Now, thousands of square kilometres of Borneo are again, with peatlands releasing huge amounts of carbon dioxide.

Warm weather and drought can also wilt crops. The Met Office is forecasting dry conditions in Central America, home to several major coffee producers, and India, the world’s largest rice exporter.

As a result of El Niño, India is experiencing its weakest monsoon since 2009, a major blow to the rice crop. Rainfall, which is the source of water for of the country’s agricultural areas, is on track to be below average.

Analysts expect global rice production to fall by in 2026-27, raising prices on a staple that half the world’s population relies on.

At the same time, because the areas of rising moist air have also shifted, places like Paraguay, Uruguay and southern Brazil are forecast to have more rain than usual. During the super El Niño of 2015-16, more than 100,000 people were by flooding in these areas. The UK and parts of the US are also likely to experience wetter, stormier weather.

On 26 August, global average sea surface temperature reached a new record. Seas around the world have been warming for years. But this new record is unusual because it comes in August rather than in March or April, when the global ocean is normally warmest after the austral summer. Part of the reason is El Niño.

“El Niño is adding heat to the system, but it is doing so on top of decades of human-driven warming,” Samantha Burgess of the European Union’s Copernicus Climate Change Service said in a statement.

A rare bit of good news from El Niño is that it reduces the likelihood of hurricanes hitting North America in summer and fall. These tropical storms in the Atlantic are fuelled by warm, moist air rising high into the atmosphere. But El Niño often intensifies high-level westerly winds, creating a contrast with weaker low-level winds known as wind shear that can disrupt this process.

“Tropical storms form better when they’re not being torn apart basically by the upper-level and the lower-level winds,” says Dunstone.

The Atlantic hurricane season has had the in almost 40 years, with only three named storms, all of them short-lasting. The US National Oceanic and Atmospheric Administration predicts that conditions will remain less active than normal and generate zero to two major hurricanes.

In the Pacific, however, winds are, in general, weaker than average, and the rising warm air can still generate large tropical storms. But because this convection has shifted eastward, the storms that make landfall in Asia have had more time to suck up energy from the ocean.

Amid all of this, global temperature invariably rises during El Niño, and this incredibly strong event is expected to amp it up even more than is typical. Because this comes on top of climate change, climate scientists are widely predicting that 2027 will be the hottest year ever observed.

Global temperature rise will almost certainly exceed 1.5°C. While that isn’t the long-term average that would be needed to officially fail the Paris Agreement goal of limiting warming to 1.5°C, it’s another nail in its coffin.

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And a strong El Niño is often followed by strong La Niña, a cooling in the eastern Pacific that creates its own extreme weather.

“That would generally have the opposite impacts,” says Dunstone. “That can be an extra sort of stress on systems if they are changing like that.”

Neurons have been created from a different type of brain cell that usually supports them. Nerve cell death is a hallmark of Alzheimer’s disease, but a cage of nanoparticles containing antibodies converted astrocytes, another type of brain cell, into neurons in mice with a version of the condition. This boosted the mice’s cognitive skills. The researchers behind the approach hope to test it in people in the next few years.

“We can replace lost neurons and also reverse Alzheimer’s disease progression [in mice],” says at the University of South Carolina.

In Alzheimer’s disease, which , the proteins beta-amyloid and tau misfold and form clumps, known as plaques and tangles. This leads to neuroinflammation and, ultimately, nerve cell death.

Researchers are increasingly exploring whether stimulating the growth of new neurons could treat Alzheimer’s disease and other neurodegenerative conditions. For instance, in 2020, scientists discovered that astrocytes – star-shaped cells that help neurons function – in the brains of mice with a version of Parkinson’s disease, which improved their motor skills.

This involved using CRISPR to genetically engineer the mice to deplete levels of a protein called PTBP1. This usually acts like a master switch that stops astrocytes from turning into neurons.

But such genetic approaches can alter regions of the genome you didn’t intend to target. “You can sometimes cut the wrong places, causing permanent genetic changes that may be harmful,” says Xu.

To address this issue, he and his colleagues have developed another way to deplete PTBP1. They designed a drug called TN-PTBP1 that packages PTBP1-targeting antibodies within a cage of nanoparticles that shuttles them across the blood-brain barrier.

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The drug enters cells in the brain, including astrocytes, where the antibodies bind to and substantially deplete PTBP1. After about a week, the antibodies are recycled by the cell, says Xu.

The team has now tested this in brain organoids made up of clumps of astrocytes and neurons, which were grown from human stem cells in a lab dish. This showed that TN-PTBP1 converts astrocytes into neurons.

Next, the researchers tried the approach in 12 mice that had been genetically engineered to develop a condition mimicking Alzheimer’s. Prior to receiving TN-PTBP1, brain imaging revealed that these mice had lost a substantial number of neurons, similar to what is seen in moderate-to-severe Alzheimer’s disease, says Xu. The mice struggled to build nests and performed poorly in a memory test that involved navigating a maze.

The team intravenously injected half of the mice with TN-PTBP1 twice over two weeks, while the rest received saline injections. Two weeks later, the mice that received TN-PTBP1 were able to nest and navigate the maze at a similar level to another group of mice without the version of Alzheimer’s, while the saline group showed no change. “There’s clearly an improvement, which is very thought-provoking,” says at the University of Cambridge.

When the researchers analysed samples of the mice’s hippocampi, an area of the brain involved in memory and learning, they found that TN-PTBP1 had caused new neurons to sprout in the brain.  

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They are now planning more studies in mice where astrocytes are labelled with fluorescent tags to track whether TN-PTBP1 is really behind those cells converting into neurons, says Xu. The researchers also hope to test the approach in monkeys and people in the next few years, he says.

The mice showed no signs of side effects, but future work should explore whether the newly formed neurons safely integrate into the brain’s networks without disrupting their function over the long term, says at King’s College London. “We need to check [whether] these neurons [would] be beneficial, rather than screwing up the network.”

But with proper testing, the potential of this drug could be huge, he says. It “could have an enormous effect on the treatment of many brain diseases”, including schizophrenia, motor neuron disease (such as ALS) and Parkinson’s disease, he says.