A yellow sun in an orange sky

The heatwave experienced by the UK in July 2022 broke a host of temperature records across the country. Image © Ed Connor/Shutterstock

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40⁰C heatwaves could happen every few years because of climate change

Heatwaves are becoming longer, more frequent and more intense as a result of climate change.

Records for the highest UK temperature have been set three times already in the twenty-first century and could continue to do so as global warming takes its toll.

Following a record-breaking heatwave in the UK, the Met Office has warned that temperatures of more than 40⁰C could become commonplace if the world continues to warm.

After breaching the threshold for the first time on 19 July 2022, with a provisional record of 40.3°C in Coningsby, Lincolnshire, the UK's climate and weather monitors revealed that extreme temperatures could become regular events by 2100.

Met Office Chief Scientist Professor Stephen Belcher says, 'In a climate unaffected by human influence, climate modelling shows that it is virtually impossible for temperatures in the UK to reach 40°C.'

'Under a very high emissions scenario we could see temperatures exceeding 40 degrees as frequently as every three years by the end of the century in the UK. Reducing carbon emissions will help to reduce the frequency, but we will still continue to see some occurrences of temperatures exceeding 40°C and the UK will need to adapt to these extreme events.'

The UK also broke records for its maximum overnight temperature during the same heatwave, as well as hitting new heights at weather stations around the country.

In future, the forecasting of heatwaves on land and at sea may allow preventative actions to protect human health and biodiversity before extreme temperatures arrive.

Raunds town hall in the sun

Raunds held the record for the highest temperature recorded in the UK for almost 80 years. Image © Stephen Richard McAdam/Shutterstock

How warm were the UK's hottest days?

Earth's average temperature has increased by 1.1°C since 1880 and continues to rise by around 0.15°C every decade. As a result, the last eight years have been the hottest on record, with the world only growing hotter in the decades to come.

One impact of climate change is an increased likelihood of extreme weather events such as heatwaves, making the record temperatures experienced in July 2022 much more likely in future.

Until relatively recently, the highest temperature in the UK had stood for decades, with a maximum temperature of 36.7°C being recorded at Raunds in Northamptonshire in 1911. However, it has been broken multiple times in recent years, beginning in 1990 when 37.1°C was reached in Cheltenham, Gloucestershire.

In 2003, it was broken again with a new high of 38.5°C in Brogdale, Kent before being eclipsed by a temperature of 38.7°C at the Cambridge Botanic Garden in 2019.

Aside from breaking the 40°C threshold for the first time, the 2022 heatwave has caused particular concern because of its scale. While the previous records were caused by high heat in small areas of the country, 46 separate monitoring stations across the country breached the previous temperature record.

In addition, the average temperature of the entire UK was above 30°C for the first time, leading climate scientist Mike Kendon to describe the events of 19 July as 'unprecedented.'

'Temperature records tend to get broken by modest amounts and by just a few stations, but the recent heat broke the national record by 1.6°C and across an extensive area of the country from Kent to North Yorkshire and from Suffolk to Warwickshire,' Mike says.

While it is currently uncertain when extreme temperatures will return to the UK, efforts to improve heatwave predictions and responses are already underway.

An underwater photograph of a bleached coral reef

Marine heatwaves can cause coral bleaching, and threaten reef ecosystems. Image © Sabangvideo/Shutterstock

Can we predict heatwaves?

While public and scientific awareness of heatwaves is high, their causes are not well understood. Generally, they are associated with weather systems known as blocking or persistent highs, where an area of high pressure remains over an area for longer than normal.

This is thought to prevent hot and cool air mixing, which causes temperatures to rise as warm air builds up. Dry periods in the lead-up to these events may amplify the effect by removing moisture from the soil and exacerbating extreme heat.

In recent years, scientists have made attempts to better understand how to predict heatwaves. A 2022 paper found that current European climate models could be used to anticipate how likely heatwaves will occur during the summer months.

While the model could not predict exactly when and where the heatwave could occur until much closer to it happening, advance warning of a month or two could enable public health services to ramp up their response before the heatwave is forecast, as well as allow for steps to manage fire risk and water availability.

Heatwaves in the air can also be partly responsible for marine heatwaves, which are linked with coral bleaching and fish mortality. Research published in Nature suggests that existing techniques can help predict unusually high sea temperatures as much as a year ahead of their occurrence, depending on the area of the ocean, and drive decision making to protect ecosystems.

As well as greater prediction, steps to mitigate the impacts of heatwaves will also be needed. Planting more trees, adjusting our active hours and changing how we design buildings can also contribute to a more heat-resilient world.