The incoming ‘super’ El Niño will create chaos around the world. And we are far from ready for it | Bill McGuire

If you think you have heard enough about the growing “super” El Niño, trust me, you are going to hear a lot more. What is happening in the equatorial Pacific is jaw-dropping and could well mark one of the biggest global weather upheavals in a millennium. It will spawn a string of weather catastrophes around our world in what remains of this year and in 2027, and there is no reason to think the UK will be immune.

To recap briefly, El Niño involves a heating of the central and eastern equatorial Pacific ocean. It happens every few years and is part of a natural cycle termed the El Niño southern oscillation, which switches between warm (El Niño) and cool (La Niña) phases. El Niños that see heating reach or exceed 2C are defined as “super” but this one, which is forecast to top-out at an astonishing 4C later this year, is so much bigger, the term “hyper” might be more appropriate.

El Niño is nothing new. Evidence for its existence extends back hundreds of millions of years and its ramifications have always been negative and disruptive. The difference today is that it is happening at a time when our world is heating more rapidly than ever before, and it is being supercharged as a result, leading to increasingly extreme weather.

Figuring out how much global heating alone is influencing El Niño is not straightforward, as its strength and other characteristics change naturally over time. Both El Niños and La Niñas, for example, have been steadily increasing in duration over the last 7,000 years. This is bad news in its own right, as it means the world’s weather is knocked out of kilter for even longer, but added to this, stronger El Niños are becoming more frequent as we continue to add CO₂ to the atmosphere.

There is no straightforward correlation between El Niño’s strength and the magnitude of impacts in any given part of the planet. But given the unprecedented amount of extra heat being added to the atmosphere over the Pacific, it would be reasonable to expect the world to experience exceptionally hazardous weather over the course of the next several months.

How, then, is the UK likely to fare? The Met Office has already warned of the increased likelihood of a stormy and wet autumn and early winter, so it would be judicious to start preparing now for flooding on a serious – perhaps even epic – scale. After all, the last big El Niño, in 2015–16, resulted in the most extreme UK floods on record. Stronger winds are also a big worry, as many trees weakened by this summer’s extreme drought conditions could be brought down in the powerful storms to come. A strong El Niño could also bring Arctic air to the UK later in the winter, although this is far from set in stone. Whether El Niño fosters more record-breaking heat next summer also remains to be seen.

But there are likely to be indirect impacts on the UK too, thanks to the devastating effects strong El Niños have on the global economy. While the great recession of 2008 resulted in global GDP reducing by around $2tn, the 1997–98 super-El Niño resulted in losses of $5.7tn. Much of this was due to the suppression of economic activity that can last for up to 14 years after a strong El Niño. The late-90s El Niño – the most powerful of the 20th century – peaked at 2.4C; the current one is already at 2.7C, meaning significant impacts on UK food security, cost of living and general economic wellbeing would not be a surprise.

However the UK fares in the coming months, its challenges are likely to be small beer compared with elsewhere on the planet. The effects of the strengthening El Niño are already being keenly felt, particularly across India, which is experiencing its weakest monsoon for 20 years. As El Niño peaks later this year, and slowly subsides, the west coast of South America and the western US can expect torrential rains, severe flooding and mudslides. Meanwhile, heatwaves, drought and wildfires will be the order of the day across the Amazon, south and south-east Asia and much of Australia. One tiny positive is that Atlantic hurricane activity tends to be damped down during El Niño years, but this is more than made up for by the revving up of Pacific typhoons.

California, in particular, is bracing itself for the worst, primarily because past super-El Niños have brought some of the wettest periods in the history of the state. This is because El Niño years tend to favour the formation of “atmospheric rivers” – streams of exceptional precipitation that track across the state from the Pacific for days at a time, dumping colossal amounts of rain. Such conditions contributed to the great flood of 1862, which left a vast area of the state under water, including a 480km-long stretch of the Central Valley. The biggest worry is that this unprecedented El Niño will see the realisation of a megastorm worst-case scenario known as the ARkStorm. If it does, expect millions of homes and businesses to be flooded, long-term damage to infrastructure, and economic losses totalling almost $1tn. Given, too, that tech companies would be severely impacted, the knock-on effects could result in another hammer blow to the global economy.

The effects of the El Niño will be felt well into 2027, almost certainly ensuring that next year is the hottest ever recorded, possibly by some margin. It would not be unexpected for the average global temperature to reach at least 1.6C above preindustrial levels, and quite possibly 1.7C or more.

Every tonne of CO₂ added to the atmosphere helps El Niños get stronger, and it would be nice to imagine that the coming monster might prove a wake-up call. But no. Governments continue to row back on green policies and fossil fuel corporations still plan for expansion.

As this year’s super-El Niño looms large, the UK government advises us to stock up on food while it prepares to greenlight the extraction of more fossil fuels from the North Sea. Cognitive dissonance doesn’t even begin to describe the idiocy of such thinking. You couldn’t make it up.

• Bill McGuire is professor emeritus of geophysical and climate hazards at UCL. His latest book is The Fate of the World: A History and Future of the Climate Crisis