Stormy autumn, cold winter - how might El Niño affect the UK weather?

Across the Pacific Ocean, El Niño is developing, a phenomenon with the potential to significantly impact global weather patterns, including the United Kingdom. While its most severe effects are likely to be observed in Peru and Ecuador, with heightened risks of flooding and landslides, and droughts and wildfires in Australia, the disruption to global wind patterns means the consequences will ripple worldwide.

The Met Office predicts the UK's autumn and early winter could be wet and stormy due to this developing El Niño event, which has reached unprecedented levels in recent history.

Professor Adam Scaife, the head of long-range forecasts at the Met Office, notes that this El Niño is the strongest in living memory. He adds that forecasters have already detected signs of increased rainfall and storminess in the UK, particularly from November to December. This aligns with the intense winter of 2015-2016, which coincided with a strong El Niño event and experienced extreme flooding.

However, following a record-breaking hot summer in the UK, the prospect of wet autumn weather may seem like a relief. Nevertheless, climate change is making more intense rainfall events more likely, so these storms and downpours will also pose a flood risk.

Strong winds associated with El Niño can lead to damage, transportation disruptions, and power outages. Although El Niño can sometimes be linked to cold spells in late winter, this connection is not strong, and past evidence is mixed. For instance, the "Big Freeze" of winter 2009/2010, which was the coldest in three decades, coincided with an El Niño, while 2006/2007, another El Niño winter, brought unusually warm conditions.

Experts suggest that during El Niño winters, we may experience a weaker stratospheric polar vortex in late winter, leading to more frequent disruptions of the polar vortex, which could increase the likelihood of cold weather late in winter.

However, the further forecasters look into the future, the more uncertain the prospects become. Thus, while El Niño may heighten the chances of cold weather early in 2027, this is not guaranteed. Globally, a very strong El Niño typically raises average temperatures by 0.2°C. While this might seem minor, it, coupled with human-induced climate change, could increase the risks of heatwaves worldwide.

Dr. Akshay Deoras, a climate scientist at the University of Reading, emphasizes that long-term global warming remains the more significant driver of the UK's rising temperatures and increased risk of extreme heat. Nonetheless, the additional warming from El Niño, combined with the UK's already warmer climate, might provide the conditions for a hot summer.