Super El Nino: It’s hot now, but time to brace for what is coming next

 There’s definitely something coming. We’re very confident about that, and it looks like it will be a big event.”

Adam Scaife, head of long-range prediction at the UK Met Office, recently gave this somewhat ominous proclamation. He was talking about the potential approaching El Nino – possibly so strong it may be classified as a “Super El Nino” – and warned it could “even be of record strength”.

The El Nino effect is a natural, cyclical climate pattern in the Pacific Ocean, characterised by the warming of surface ocean temperatures in the central and eastern equatorial Pacific.

Under normal conditions, trade winds blow westward along the equator, pushing warm water from South America towards Asia; cold water rises from below to replace this warmer water in a process known as upwelling. But El Nino throws all that into disarray. Trade winds aren’t as strong, and so the warm waters head east towards the Americas instead, forcing the Pacific jet stream south of its neutral position.

Upwelling weakens or stops altogether; without the nutrients being transported from the depths to the shallows of the ocean, there are fewer phytoplankton off the coast, which in turn impacts fish that eat phytoplankton, which in turn impacts everything that eats fish. Entire ecosystems are disrupted by the change.

Some areas in the northern US and Canada become hotter than usual and experience droughts; the US Gulf Coast and southeast experience wetter weather than usual, and increased flood risk.

But the impact of El Nino is far wider than just the Americas: it changes weather on a global scale. Countries around the tropical Pacific, like Chile and Indonesia, are strongly affected, with the former more likely to get heavy rainfall and the latter more likely to suffer droughts. We could see an extreme Pacific typhoon season and a more docile hurricane season in the Atlantic, a much more varied and unpredictable South Asian monsoon season, and a drier-than-normal Australia.

In the UK specifically, the El Nino effect is usually weaker but can lead to more dramatic weather extremes: winter temperatures tend to be colder, especially later in the season, while in summer the mercury soars. This current heatwave might prove the tip of the iceberg.

“Summer temperatures could certainly be impacted, possibly this year, but more likely next, as the planet heats up,” says Professor Bill McGuire, emeritus professor of geophysical and climate hazards at University College London and author of the new book The Fate of the World: A History and Future of the Climate Crisis. “I wouldn’t be at all surprised to see 40C-plus heat.”

What tips an El Nino into “super” territory is all to do with water temperature. “If sea surface temperatures there are more than 0.5C above normal for the time of year, we say that those are El Nino conditions,” according to Mark Roulston, senior research fellow and director of operations for Lancaster University’s Climate Risk and Uncertainty Collective Intelligence Aggregation Laboratory (Crucial).

“A ‘Super El Nino’ is often defined as when these temperatures are more than 2C above normal for the time of year, so a more extreme version of the El Nino phenomenon.”

I wouldn’t be at all surprised to see 40C-plus heat

Professor Bill McGuire, UCL

Ocean warming has been rapid over the past few weeks and is expected to continue over the next few months, peaking in autumn. While El Nino conditions can sometimes last for as long as 18 months, the more extreme conditions associated with a Super El Nino tend to be shorter-lived, more in the region of two to four months.

Crucial’s predictions currently indicate that there is a more than 85 per cent chance of El Nino conditions prevailing during the upcoming winter (December, January and February), and around a 45 per cent chance that the conditions will be extreme enough to be classed as a Super El Nino.

The National Oceanographic and Atmospheric Administration (NOAA), which forecasts that El Nino will begin within the month, has crunched the numbers and given a 66 per cent chance that it will be strong or even very strong by this winter. More than half of the European Centre for Medium Range Weather Forecasts (ECMWF)’s models, meanwhile, are suggesting a potential ocean temperature increase of over 2.5C by the autumn, putting it well within “super” range.

There is growing confidence from scientists that this potential El Nino could be notably strong.

“My personal opinion is that we will see the 2.5C threshold broken, and may even approach 3C – challenging the strongest El Nino on record in 1877-8,” advises Professor McGuire.

While organisations around the world have their own exact definitions and thresholds for what constitutes El Nino conditions, this will be “such a significant event, if it happens, that it will be above all of those thresholds and there will be no doubt that we’re in an El Nino,” said Grahame Madge, climate science communicator at the Met Office. “Scientists are telling us that this could be the strongest El Nino event so far this century, comparable to the notable El Nino event in 1998.”

While significant El Ninos occur around every two to seven years, Super El Ninos are rare. Only three others have exceeded the 2C threshold since the mega one recorded in 1877-8: 1982-3, 1997/8 and 2015-16. This latest El Nino could see 2027 become the hottest year on record, pushing global average temperatures permanently past the benchmark of 1.5C above pre-industrial levels set by the Paris climate agreement.

While having a roasting summer might sound appealing to some, Super El Ninos tend to result in widespread humanitarian, as well as environmental, disaster: food shortages and famine due to severe droughts; an increased risk of devastating floods and wildfires. The 1997/8 Super El Nino resulted in the death of an estimated 16 per cent of all the world’s coral reefs.