How cities around the world are learning to cope with heatwaves

It probably hasn’t escaped your notice that it’s very, very hot. A heatwave is spreading through most of Europe, and temperatures could climb to record levels in the UK this weekend. 

Of course, how hot it is for you depends on where you are in the country. If you’re in London, you’ll be suffering the most thanks to something called the “urban heat island” effect.

This refers to cities being much warmer than other parts of a country during heatwaves thanks to concrete and asphalt absorbing and radiating heat while tall buildings trap heat at street level.

The effect is so marked that cities can be as much as 10C hotter than surrounding areas during a heatwave – and this can be dangerous for people’s health and wellbeing. 

As shown below, some cities are coming up with ways to deal with extreme weather, from planting more street trees to “cool spot” maps for the public. It should be said, of course, that countries in the global south who are at the sharp end of the climate crisis may not have the same resources to act.

Barcelona 

Currently, Barcelona has more trees than almost any other European city, and that’s good news when it comes to hot weather.

The 1.4m trees within the city’s boundaries are able to modify the microclimate, bringing temperatures down significantly and providing shade to protect people from the sun. 

Trees also have other benefits, such as boosting biodiversity and containing noise pollution.

And Barcelona has plans to go further, with a 20-year tree masterplan aiming to increase the proportion of land covered by trees to 30 per cent while ensuring that the species planted are resilient to hotter temperatures.

Frankfurt

Frankfurt is one of the warmest cities in Germany, and has been exploring ways to mitigate the impacts in recent years.

One innovation has been “luftleitbahnen”, which translates as ventilation corridors. 

These are stretches of land within the city which don’t have any high buildings or large stretches of trees, allowing cooler air from areas outside of the city to flow into the city.

With temperatures up to 10C lower outside the city than inside it, these corridors allow up to 40,000m3 of cold air per second to flow into the hottest parts of the centre.

Paris and Nice 

After a heatwave in 2019 that killed more than 1,000 people across France, Paris took action to mitigate against future heatwaves.

This has included the creation or designation of more than 800 “cool islands” across the city, covering parks, forests, swimming pools and museums. 

These are places that offer refuge from the heat and are linked by naturally cool walkways, with an app offering directions. 

As part of the city’s climate adaptation strategy, leaders are aiming for a cool island to be less than seven minutes away by foot from wherever somebody is in the city.

Other French cities are also mitigating against hotter weather. In Nice, urban architects have installed “pavement wetting” systems at a new transport hub, which makes pavements cooler during the summer.

Vienna 

In the Austrian capital, “cool straßen” (cool streets) offer refuge from the heat with “fog showers” that spray a fine mist into the air to cool down members of the public when temperatures climb.

These streets have also banned cars and offer outdoor seating areas for people to enjoy the sun without overheating. 

London 

Though London does get unbearably hot during some parts of the summer, the UK capital is beginning to adapt to hotter temperatures.

One innovation has been installing green roofs across the city, with more than 1.5 million square metres now installed. 

These roofs provide extra green space in dense areas, with the ability to cool temperatures during hot days.

A “cool spaces” map also offers information on where members of the public can go to find refuge when temperatures climb.

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Los Angeles

With concrete absorbing and radiating heat, Los Angeles in the US has begun painting its roads a lighter shade of grey, with plans to cover more than 250 city blocks.

The process has made surface temperature between 5-8C lower than if the darker colour had been left the same.