London is forecast to reach 26C on the first day of autumn in the Northern Hemisphere. this unseasonable warmth is being driven by a combination of a "Super El Nino" event and the long-term effects of climate change.
London's 26C Autumn Start and the Ridge of High Pressure
While the calendar marks the arrival of autumn, southern England is experiencing temperatures between 20C and 26C, according to the report. In contrast, Scotland and the north of England are seeing more modest highs of 16C. This temperature spike is the result of a ridge of high air pressure sitting over the United Kingdom, which is effectively drawing warm air up from subtropical Africa and Europe.
The Met Office reports that this weather pattern was initiated by a deep area of low pressure forming in the Atlantic to the west of the UK. This atmospheric setup has allowed summer-like conditions to persist well into late September, leading to scenes of beachgoers at Brighton Beach on September 22.
The 3C Sea Surface Surge of the Super El Nino
A significant driver of this volatility is the "Super El Nino," a potent phase of the El Nino Southern Oscillation. As the report says, sea surface temperatures in the equatorial Pacific are currently 3C above the average, smashing previous records months before the cycle is expected to reach its peak.
During an El Nino phase, the buildup of warm water near the surface of the Pacific Ocean drives up global temperatures. when this natural cycle intersects with the existing baseline of global warming,the result is a heightened probability of warmer-than-normal weather across the UK and other regions in the coming months.
A 130-Times Higher Probability of Extreme Heat
The current heat is not an isolated incident but part of a systemic shift. A rapid attribution study by the Met Office found that the record-breaking summer preceding this autumn was made 130 times more likely due to climate change caused by the burning of fossil fuels.
Professor Friederike Otto of Imperial College London notes that every heatwave is now made more intense and more frequent because of atmospheric emissions. Similarly, Professor Hannah Cloke of the University of Reading explains that while high pressure creates the immediate sunny days, human-caused climate change has shifted the background temperatures, meaning that when the right weather patterns align, the resulting heat is more extreme than in previous decades.
Dr. Lucy Clarke's Warning of a Stormier Winter
The immediate warmth may be a precursor to more violent weather. Dr. Lucy Clarke of Nottingham Trent University suggests that these conditions could increase the likelihood of a milder, wetter, and stormier period later in autumn and early winter. Professor Nigel Arnell of the University of Reading adds that the current warmth is supported by the persistent position of the Jet Stream, which allows hot southern air to reach the UK.
However, several questions remain regarding the long-term seasonal trajectory. While Dr. Lucy Clarke mentions the possibility of increased cold spells later in winter , it remains unverified whether these will be severe enough to offset the current warming trend. Additionally, the report focuses heavily on the Met Office and academic perspectives, leaving the specific economic impact on UK autumn agriculture and energy demand unaddressed.
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