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.

Super El Niño could lead to mega CO2 emissions from fires in Indonesia

Intense fires are already burning in Indonesia, and there could be much worse to come as the Super El Niño ramps up

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.”

Picture the world 100 or 200 years from now. What are you imagining? Hotter temperatures, melting glaciers or alpine places without snow? With heatwaves happening across Europe this summer, it’s not that hard to visualise.

Now picture Europe in a deep freeze where temperatures hit -20°C in London. Both of these scenarios might be the future we’re heading for, thanks to climate change. And there’s an even more worrying indicator: while almost the entire planet has been warming, there’s one patch in the North Atlantic Ocean just south of Greenland where temperatures have been falling.

Scientists call it the “cold blob”, and some think it could be a warning that one of Earth’s most important climate systems is beginning to change and may soon hit a tipping point where climate change no longer happens gradually. If this system flips, it could have devastating consequences that change all of our lives as we know them.

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.”

“The El Niño has blossomed. It is off the charts. Usual measures of El Niño have blown past prior record levels in the period with good data, even though maximum effects are still several months in the future.”

So writes renowned climate scientist James Hansen at Columbia University in New York in .

There are different ways of measuring El Niños, which occur when warm surface waters spread eastwards along the equator across the surface of the tropical Pacific Ocean. Hansen thinks the best measure is how much warmer than usual the upper 300 metres of the eastern tropical Pacific becomes.

“Our preferred metric, the heat anomaly in the upper 300 meters of the Equatorial Pacific Ocean… already exceeds the 1997-98 super El Niño,” he writes.

A more common measure, called the Niño3.4 index, is based on how much warmer than usual the sea surface temperature is in the Pacific in the long rectangle between 5 degrees north and south of the equator, and between 120 and 170 degrees west.

“The more common Niño3.4 metric, sea surface temperature… in the equatorial Pacific, also far exceeds prior values,” Hansen writes.

But at the Met Office, the UK’s national weather service, says the Niño3.4 index has not yet exceeded previous super El Niños. “The anomaly in Niño3.4 is currently about 2 degrees above the norm which is very high for this time of year but not quite as high as the anomaly at the peak of the 1997/1998 El Niño which was around 2.5 degrees,” Scaife told 91av.

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The disagreement on the Niño3.4 index might partly be because this index is usually expressed . By contrast, the daily Niño3.4 value before dropping back slightly.

“In this case, I would agree with Jim,” says at the California Institute for Water Resources. “Niño3.4 values are clearly now the highest on record for the time of year, and are expected to remain so for the rest of the calendar year.”

Using a running mean with a long lag is misleading in a rapidly evolving situation like this, says Swain.

However, during November 2015 the daily Niño3.4 reached nearly 3.1°C, so the current event is not yet as strong as the 2015 one on this measure, either. It appears Hansen meant to say the Niño3.4 index exceeds values for this time of year, as Swain says. 91av has asked Hansen for clarification, but had no response at the time of publication.

“Under the standard El Niño metric region it’s still currently the third strongest event on record,” says at Berkeley Earth. “But upper 300m heat is generally a leading indicator of what we will see at the surface.”

“I agree that this El Nino is the biggest on record,” says at the National Center of Atmospheric Research.

What’s clear is that this developing super El Niño will soon exceed previous events on all measures. “I have never seen an El Niño signal this intense in our forecasts,” Scaife said in . “If the forecast is accurate… then 2026 will far exceed our recent experience of El Niño and its worldwide climate influences.”

While Hansen is comparing the developing super El Niño to other modern events for which we have direct temperature records, at Newcastle University in the UK thinks it could also exceed historical events suspected to be even larger.

“The super El Niño evolving in the Pacific will likely be the biggest ever recorded, reaching or exceeding the levels of the 1877-1878 El Niño which caused widespread impacts, including famines and around 50 million deaths (3-4 percent of the global population at the time), mostly across Asia and South America,” Fowler said in a statement.

Climate models projecting higher warming for a given level of carbon dioxide have been discounted as unrealistic, but a new way of assessing models suggests they are accurate.

“For a given emission trajectory, we expect warming to be 25 per cent higher,” says at ETH Zurich in Switzerland.

The conclusion has enormous implications. For instance, a project called the currently projects that average global surface temperatures will rise by 2.6°C above pre-industrial levels by 2100 if countries implement existing policies. Gyuleva’s team’s results suggest we are instead heading for 3.25°C.

How much the world will warm depends on how much more CO2 we put into the atmosphere and how the planet responds to that CO2. Different climate models vary in how much warming they project for a given CO2 level. For instance, some models suggest that a doubling of CO2 will result in the average global surface temperature increasing by around 1.6°C above pre-industrial levels in the short term. Others suggest it could be as high as 3°C.

“The range is big, and it really matters,” says Gyuleva. “So the point is to find out which ones are right.”

Previously, this was done by using climate models to simulate the recent past. The models are fed data on greenhouse emissions over the past century or so, and their projected climate response is compared with what actually happened.

For the last report by the Intergovernmental Panel on Climate Change, a lot of these models simulated more warming than had happened, so were discounted. Based on the remaining models, the panel’s last report concluded that a doubling of CO2 would result in between 1.2°C and 2.4°C of warming in the short term, with a best estimate of 1.8°C.

But there is lots of variability in Earth’s climate. For instance, during the La Niña climate pattern, cooler seawater from deeper down spreads across the ocean, resulting in cooler surface temperatures. So, Gyuleva and her colleagues have filtered the historical climate record to try to remove the effect of variability due to phenomena like La Niña.

Their results suggest that natural variability limited temperature rises between 1981 and 2014 – a period that includes the so-called global warming hiatus in the first decade of the 21st century. “It’s really exactly this period 1981 to 2014, which was used in the previous papers, where you see the strongest bias down,” she says. “It was really bad luck.”

Correcting for this bias alone leads to higher estimates of the warming expected from a doubling of CO2. But Gyuleva’s team also assessed models using a new approach. Instruments on several satellites have been measuring how much short-wave radiation from the sun enters the atmosphere, and how much long-wave radiation is emitted. The difference between how much heat energy enters the atmosphere and how much leaves is the most fundamental measure of global warming.

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So, how well models project the trends in incoming and outgoing radiation as the world warms can be seen as a better measure of their performance than their projections of surface temperatures. But because the satellite measurements required to do this only began in 2001, this kind of assessment has only recently become possible.

The team found the models that best match the observed trends in short-wave and long-wave radiation project much greater warming. Based on the models that perform best at both kinds of assessments, the team concludes that a doubling of CO2 will lead to a rise of between 1.9°C and 2.6°C, with a best estimate of 2.25°C. “Our results need to be confirmed by more evidence from different sources before we can be fully confident,” says Gyuleva.

“This seems to be a sound approach,” says at the University of Oslo in Norway.

“In my opinion, the filtering out of natural variability is a valuable step forward,” says at Duke University in North Carolina, although he isn’t yet convinced that the short-wave and long-wave trends are a good way to assess models.

“I think it’s a plausible conclusion and a reasonable approach,” says at the University of New South Wales in Sydney.

But the findings are based on climate models, and none of them reproduces the key phenomena very well, says Sherwood. “To do a better job of this we really need better climate models. On the other hand, the steep temperature rises of the last few years are going to lead to higher estimated ranges regardless of method.”

In climate jargon, what Gyuleva’s team has estimated is known as the transient climate response. It is just one of three types of climate sensitivity, which vary in terms of the timescales involved.

Coral reefs have fuelled severe global warming in Earth’s past

Over the past 250 million years, periods when coral reef growth has peaked have coincided with big rises in sea temperatures

In the decades after a doubling of CO2, various feedbacks will kick in that lead to further warming, such as the continued warming of the oceans. The response after these medium-term feedbacks have kicked in is known as the equilibrium climate sensitivity. Last year, it was shown that the trends in short-wave and long-wave radiation suggest the equilibrium climate sensitivity is higher than previous estimates.

There are also very slow feedbacks that take centuries or more, such as the melting of ice sheets. Estimates of this earth system sensitivity – the full response to a doubling of CO2 over many millennia – are as high as 7°C.

However, if atmospheric CO2 levels were lowered by carbon removal, some of the longer-term consequences would be avoided.