Meteorological and environmental prediction organisations confirm June as the hottest on record for the UK, and Tuesday 4 July as the hottest day ever recorded worldwide. We asked climate change researchers at the National Centre for Atmospheric Science to explain the role of climate change and El Niño in record-breaking temperatures. 

The Met Office recorded an average mean temperature of 15.8°C for June 2023 in the UK, the highest since documented measurements began in 1884. It was 2.5°C higher than average, and surpassed the previous hottest UK June by 0.9°C. The previous record of 14.9°C was reported in 1940 and 1976.

On Thursday 6 July the US National Centers for Environmental Prediction confirmed it was the hottest day ever recorded globally, with the average global temperature of 17.23°C, which surpassed the record of 17.18°C set on 4 July. The previous record of 17.01°C was set just a day earlier on 3 July.  Before that the highest global temperature on record was 16.92°C, recorded in August 2016.

“Rapid warming means we must expect extreme event records to be broken – not just by small margins but quite often by very large ones,” says Professor Rowan Sutton from the National Centre for Atmospheric Science and University of Reading.

“This is a consequence of the extraordinary rate of climate change. Whilst it may not seem rapid to us, Earth is warming at a rate that is unprecedented in the history of human civilisation,” emphasises Professor Sutton. 

The record-breaking temperatures globally are thought to be a combination of climate change and the climate pattern El Niño. 

The average temperature at the Earth’s surface has risen by about 1°C since the pre-industrial period, and 17 of the 18 warmest years on record have occurred in the 21st century. 

Human-induced climate change means that summer weather and hot spells are occurring against a warmer background climate. Therefore, record-breaking temperatures are likely to be higher than average by a significant margin, and more frequent. 

As El Niño comes into effect this year – a climate pattern that acts as a giant heat source in the tropics – it is not certain how temperatures in the UK will be affected, but more record-breaking global temperatures are anticipated. 

Dr Kieran Hunt, climate scientist at the National Centre for Atmospheric Science and University of Reading, explains: “We know that El Niño can warm the planet significantly, up to about 0.2°C averaged over a given year.” 

As seen in the recent marine heatwaves, a combination of the effects of human-induced climate change and El Niño resulted in unusually high temperatures in the North Atlantic, Pacific and Antarctic oceans.

More record-breaking global high temperatures, made possible by climate change, are likely to occur in the coming decades. Dr Hunt adds: “Given that global warming has resulted in the ten hottest years on record all occurring since 2010, I think it’s very likely that even a moderate El Niño would result in 2024 breaking the record.”