The UK's Met Office has forecast that the El Niño event currently developing in the Pacific Ocean will be the strongest in over a century, with sea surface temperatures expected to rise more than 3°C above normal. The forecast, issued on Friday, warns that the event could push global temperatures to record levels and bring significant weather disruptions across the world.

An unprecedented event

Adam Scaife, head of long-range forecasting at the Met Office, described the forecast as "an unprecedented event", telling the BBC that "We are expecting the biggest El Nino for over a century, peaking at something over three degrees -- that is unheard of in modern climate records." He added, "I have never seen an El Nino signal this intense in our forecasts."

Typically, El Niño leads to sea surface temperature rises of between 1 and 2 degrees Celsius. The Met Office's forecast of more than 3°C would make this event "the largest since the 19th century", according to the agency. The Climate Brink dashboard, which aggregates forecast models using data from the US National Oceanic and Atmospheric Administration, projects the event could peak at a 3.9°C anomaly this November, well above the roughly 3°C anomaly seen during the 2015-16 El Niño, which was previously the strongest on record.

Pacific sea-surface temperatures are currently running about 2.6°C above the rolling 30-year average, according to the same dashboard. Some climate groups have projected even stronger warming, possibly 4°C above average, according to the BBC. Dr Zeke Hausfather, a climate scientist at Berkeley Earth, told the BBC that "It's not beyond the realm of possibility to say this might be the strongest El Niño event in 500 or even 1,000 years."

Global and regional impacts

The Met Office warned that the event will have strong effects throughout the tropics, with "really severe droughts in places like South America, and the West Pacific", Scaife said. There is also a heightened risk of drought in southern Africa and north-east Australia, while north-western Europe, including the UK, is likely to see wetter and stormier conditions this autumn and early winter.

Scaife said the forecast predicts "increased rainfall and storminess in the autumn here in the UK around November time". Met Éireann, Ireland's national meteorological service, has also warned of "intense" storms and rain, with climatologist Paul Moore noting that well-above-average sea surface temperatures increase atmospheric moisture and can intensify rainfall events.

The Met Office also said the El Niño could make 2027 the hottest year on record. Dr Nick Dunstone, a science fellow at the Met Office, said "2027 is very likely to replace 2024 as the warmest year on record and be another year to temporarily exceed plus 1.5C above the preindustrial period." Global temperatures in 2024 already exceeded 1.5°C above pre-industrial levels, according to multiple reports.

Impacts on India's monsoon

The El Niño is already affecting India's monsoon, which is currently running 13% below normal, with around 40% of the country receiving at least 20% less rainfall than average, as reported by Livemint. The Met Office said the El Niño is causing well below normal rainfall in India, and the India Meteorological Department projects the full season at 90% of the long-period average, its lowest in 11 years.

Madhavan Rajeevan, atmospheric physicist and former secretary of India's earth sciences department, told The Telegraph that "almost all exceptionally strong El Niño events are associated with large deficits in the monsoon or drought." However, he noted that the phenomenon is part of an oscillatory system that will eventually reverse. Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology, said temperatures could remain unusually high for months even after the El Niño weakens.

India's monsoon accounts for about 75% of the country's annual rainfall, making the forecast particularly significant for agriculture. Kulwinder Kaur Gill, a crop scientist at Punjab Agricultural University, told The Telegraph that in well-irrigated states like Punjab, the link between monsoon rainfall and agricultural output can be counterintuitive.

UK's already-strained infrastructure

The UK has already experienced a summer of extreme heat and drought. The country recorded its hottest day of the year in mid-August, with temperatures reaching 38.1°C in west London. The heatwaves in May and June led to an estimated 2,700 excess deaths in England and Wales, as reported by My London.

The extreme weather has put pressure on infrastructure, including the railway network. Two trains derailed within 24 hours during the UK's fifth heatwave in August, which Network Rail said "presented exceptional challenges to the railway". Xueyu Geng, a professor of ground engineering at the University of Warwick, told The Guardian that Britain's railways were not designed for hot weather, and that adaptation is needed.

The UK has also seen drought conditions, with 71.3% of England and all of Wales in drought, and the driest July in 190 years, according to The Guardian.