The blistering temperatures of future heatwaves in the UK have been revealed on a new website, which allows users to search for their area by postcode to see what an extreme hot spell will feel like in the 2070s.

Developed by researchers at the University of Bath, the COLBE site shares details of the intensity of likely heatwaves in the 2070s. Measured against previous weather events typical of the 1990s, the localised graphs on the site show heatwaves will be on average up to 10° Celsius hotter.

The Creation of Localized Current and Future Weather for the Built Environment (COLBE) project calculated what likely ‘extreme weather weeks’ in the UK will be like, by applying a sophisticated new simulation algorithm to official Met Office data and long-term predictions.

The researchers hope the data will help the public understand the true danger of climate change for the UK, which lies not in the elevation of average temperatures, but in considerably more intense heatwaves. Much of the south of the UK will experience heatwaves like that of the 2003 European heatwave, which left 14,000 dead in Paris alone.

In addition, they hope to encourage homeowners, the construction industry and policymakers to incorporate building features commonly used in hotter climates in new build and existing buildings, so occupants can better cope with the weather extremes of the future.

David Coley, Professor of zero-carbon design and a member of Bath’s Centre for Regenerative Design & Engineering for a Net Positive World, led the research. He said: “Messages about the urgency of climate change often focus on +2°C average temperature rises. People don’t think in terms of averages, or in terms of seasonal climate – they think in terms of weather, and what it’s like during extreme periods. Hence, we have developed a tool so that people can directly see one impact of climate change where they live or work.

“This new tool compares a typical heatwave in the 1990s to one in the 2070s. It indicates that unless action is taken, deaths caused by heat will be common.

“In many locations what is currently a high midday temperature will be happening overnight, and over several days during a heatwave – it is this extreme overnight temperature that will lead to problems for the elderly. Low-probability events that would have been once in a hundred years will be happening around once every three years.

“During heatwaves the UK will feel more like Bangkok, with high humidity and unrelenting hot temperatures.”

Expanding on research published in 2023, the COLBE website now allows people to see likely heatwaves for the 2070s in locations around the UK by inputting a postcode, or location coordinates. Graphs visually show the difference between a heatwave from the 1990s, and the forecast 2070s seven-day ‘extreme week’ calculated by the team’s new algorithm.

The site holds detailed weather projections for more than 11,000 UK locations. The predictions predict peak summertime temperatures of 41°C in London, and one-week averages of 28°C in large parts of southern England.

The researchers say that the construction industry, and regulators, urgently need to adopt climate change preparedness thinking in their work. Prof Coley adds: “Architecture needs to create buildings which safely access all of the nighttime cooling potential, and don’t overheat during the day. It is worth noting that in the Paris heatwave, for similarly aged people, the mortality was lower in the homeless. People were literally killed by their homes.”

Forecasting extreme weeks

Using weather generator computer code and a new sophisticated algorithm, the team built upon Met Office seasonal climate predictions to create realistic and detailed week-long, hour-by-hour, weather projections for 11,326 UK locations at 5km square intervals.

After inputting the climate prediction data into the code, the weather generator produced 3,000 examples of weather forecasts for the 2070s. The team then looked for heatwaves and examined how they changed over time.

The team says that this new focused approach of creating short-term weather predictions marks a change from most research into future temperatures, and that it could help communicate publicly the challenge of climate change and help preparedness efforts.

Prof Coley adds: “We have focused on calculating the hour-by-hour temperatures we would observe in a likely extreme seven-day period. The real danger lies not in moments or short periods of extreme heat but over sustained periods, where overnight temperatures do not drop enough to allow people to recuperate and cool down.

“A normal assumption is that night-time temperatures are going to be significantly lower than in a day. What we have calculated suggests we should forget that assumption.”

Pressing need to integrate climate preparedness into planning

The COLBE project was designed to give citizens, architects, engineers, planners, and policymakers the tools to protect themselves and plan future buildings or regulations, allowing them to select the correct constructs and materials.

Prof Coley adds: “Unshaded windows facing the sun are a no-no. Adopting Mediterranean-style features like smaller windows on aspects that face the sun, as well as features like shade-creating awnings, bars over windows to maintain security while improving airflow, and features like larger trickle vents and mechanical heat recovery systems or quiet low-speed fans, are important.

“Some of these are not part of our traditional architectural language in the UK, but adding even a 30cm deep shade above a window can make a dramatic difference in reducing solar heat gain to the window, and hence the house. Moderating against solar heat gain is very doable. We could have a whole industry based around creating secure, heat-balancing products for when windows are replaced, but it will not happen until people understand the reality of the impact that more extreme temperatures will bring.”

You can search for your local heatwave in the UK on the COLBE website at: https://colbe.bath.ac.uk/survey.html. More detailed files, created for building professionals to use with building simulation software, are also available.

The findings were published in the paper The week that will be: Communicating the impact of climate change via extreme weeks in Building and Environment.