Can cities adapt to an era of extreme heat?

The ancient Greeks pioneered a range of innovations to cool their houses during the summer, planting trees to provide natural shade and designing buildings to limit which spaces felt the full blast of the sun’s rays.

Thousands of years later, their descendants are drawing upon the same kind of ideas to cool down the city of Athens. One of Europe’s hottest cities, Athens is a densely built-up urban sprawl that suffers from a deficit of green space. City planners are looking at ways to create more shade, such as widening pavements and planting more trees.

But that creates some modern dilemmas the ancient Greeks did not have to think about. At a meeting earlier this month in Athens, with outdoor temperatures at 33C, architects, engineers and city officials pondered the consequences of making space for more trees. Where would all the displaced parking spaces go? And how wide do roads need to be for ambulances to get down them?

After a week that has underlined the threat that extreme weather poses to modern urban life, cities across Europe are desperate to find solutions both big and small.

So far this month, parts of western France, Portugal and Spain have been ablaze as they set record temperatures. Earlier this week, temperatures in the UK surpassed 40C for the first time ever, sparking wildfires and halting public transport.

In the Athens region, which last year endured one of its most intense heatwaves on record, a hospital on the outskirts of the city had to be evacuated earlier this week because of wildfires. Climate modelling shows these kinds of heatwaves are likely to become more frequent and more intense globally.

The stakes are high, both for public health and the economy. By 2030, the consultancy Vivid Economics has estimated, the US alone could lose an average of $200bn annually from reduced worker productivity due to heat stress. Much of that would be felt in urban areas, which are home to a growing proportion of the world’s population. A UN report by the world’s top climate scientists this year estimated that by 2050 “urban heat stress” would reduce an individual’s capacity to work by approximately 20 per cent in hot months.

Extreme heat blankets entire regions, but cities feel it more acutely thanks to the so-called urban heat island effect. Many of the materials that buildings and roads are made from — such as tar and concrete — absorb and retain energy from the sun’s rays, warming their surroundings. The effect is particularly pronounced at night, when the difference between the temperature in a city and that of a nearby green space is often greatest.

Athens is one of a range of cities worldwide trying to figure out how to tackle this new era of extreme heat. Seven cities across four continents, including the Greek capital, have now appointed “chief heat officers” to advise officials on how to mitigate against heat-related risks. The C40 network of mayors of nearly 100 cities, meanwhile, shares data and best practices on how to cool urban centres and make them more resilient.

After consecutive summers of record-breaking heat in Europe, municipalities are preparing to take action — from planning more resilient infrastructure to introducing early warning systems to help the public understand the dangers associated with heat.

Fortifying a city’s infrastructure, however, is a massive job that will cost billions. There is also the knotty bureaucracy of local planning to navigate — different parts of a road might be managed by different authorities, for example — and the two combined mean the pace of change is slow at a time when climate change is accelerating.

“There’s always bureaucracy and red tape that makes things slower,” says Athens mayor Kostas Bakoyannis. “Also, the fact that we’re living with the legacy of the economic crisis . . . We’re trying to move as quickly as we can.”

Many places in Europe have had to lurch into emergency mode this summer to deal with aggressive wildfires — including London, where the unprecedented spectacle of blazes on the fringes of the capital shocked citizens and scientists alike.

“The fires that we saw [in the UK] were something new,” says Thomas Smith, assistant professor in Environmental Geography at the London School of Economics. “We’re entering the realm of what we see in France, Spain and Greece.”

That requires planning ahead, not just reacting. “The way we’re dealing with heatwaves at the moment is essentially to implement our emergency plans,” says Nigel Arnell, professor of climate system science at the UK’s University of Reading. Instead, cities need to make sure that new developments and infrastructure are “designed to cope with the extremes that we’re definitely going to see . . . It’s a government issue that we really need to address.” 

Getting the message out

In Athens, chief heat officer Eleni Myrivili says she thinks of the job as having three parts: raising awareness, preparing for extreme heat and redesigning the city.

Since Greece is used to hot temperatures, “a lot of people don’t take heat exposure very seriously,” says Myrivili, who has just taken on a new role as the first “global chief heat officer” at the UN Human Settlements Programme, to integrate the issue into the agency’s work on urban development. “They don’t understand that it has serious health effects and is really dangerous,” she says.

The further the human body gets from its core temperature of 37C, the more distressed it is likely to become. Heat stress can result in exhaustion and dizziness, and lead to seizures and organ failure. Key areas of the brain, such as those responsible for problem solving, can also be impaired by overheating.

One of Athens’ recent awareness-raising initiatives — funded by the Washington-based Adrienne Arsht-Rockefeller Foundation Resilience Center — is a new heatwave categorisation and warning system, which Myrivili describes as a “game-changer”.

Scientists analysed two decades of Athens weather data, such as temperature and humidity, as well as mortality data, in order to establish which conditions were most likely to result in death — and can now rank incoming heatwaves from one to three, with the most severe denoting “extreme temperatures” and “major health risks”.

Similarly, the Spanish city of Seville launched a heatwave-naming pilot this summer — similar to the longstanding system of naming storms and hurricanes. The scheme “will allow public authorities to better communicate the risks associated with heat” and respond more effectively, including by warning people about what is coming. Since storms are named alphabetically, from A to Z, Seville will go the other way, from Z to A, starting with Zoe, Yago and Xenia.

Naming heatwaves “is the big hammer tool to save lives from heat, it’s a big policy move,” says Kathy Baughman McLeod, director of the Arsht-Rockefeller Foundation, which has also supported Seville’s project. The system draws attention to the problem [of heat] and sends a message that the authorities are “getting in front of it”.

Such measures will also force scientists to define more precisely when a period of unusually hot weather starts and ends, says Niko Speybroeck, from the Em-dat international disasters database — a task that can be more of a challenge for heatwaves than for other types of disaster, such as floods.

This information — which is not always collected and can be particularly patchy in developing countries — is crucial, he says: it allows researchers to predict and plan for heatwaves, and analyse which combinations of weather are the most dangerous. “The recording and reporting of health-related issues should be improved, there should be funding dedicated to that,” he says.

Building for heat

In the longer term, some cities will need to implement costlier measures if they want to build resilience and prevent services from failing when temperatures jump.

In the UK, the unprecedented July heat brought chaos to airports and railways, as the nation’s train tracks — which were not built for hot weather — overheated, and London’s Luton airport was forced to cancel flights because the heat caused a small section of the runway to lift up.

Cities are often not good at dealing with the “big systemic picture”, says Arnell. There is a “big job” to do retrofitting infrastructure, he says, as “most of what we’ve got will still be here in 30-40 years”.

Ripping up tens of thousands of miles of track and replacing them with more heat resistant rails, however, would be a massive, complicated and hugely expensive job. In July, the UK’s transport secretary Grant Shapps warned that it could take “decades” to make Britain’s transport system more resilient to heatwaves.

Globally, governments have been unwilling to make those kinds of investments. This year’s UN climate report said about $384bn of “climate finance” had been invested annually in cities in recent years, around 10 per cent of what was needed for “low-carbon and resilient urban development”.

Britain also has the oldest housing stock in Europe, with one in five dwellings built before 1919. Many urban residential houses date back to the 19th century, and have poor insulation and limited airflow, making them hard both to heat and to keep cool.

The UK’s Climate Change Committee, which advises the government, has called on ministers to retrofit buildings and properly insulate homes to help keep them cool in summer and warm in winter.

The task would require a co-ordinated and systematic approach involving central government and local planners, and the investment would be substantial — it would cost the government billions every year. But the return would also be big: more temperate and energy efficient buildings, which are cheaper and greener to run, the CCC says.

The less environmentally friendly alternative is air conditioning, still rare in residential buildings in Britain, though more common in southern Europe. Yet even before the spiralling global energy crisis, many elderly citizens in Athens could not afford to run air conditioners, which are very energy intensive, at home, says Myrivili. “The machines add heat outside, and run on polluting energy,” she says. “We can’t air-condition our way out of this.”

The sum of small things

In lieu of big spending commitments, local planners are taking steps to make cities more bearable with small and locally specific interventions.

Smart design, such as shutters on the outside of windows, can reduce how hot the inside of a building gets. Creating shade with trees, canopies or other design features can make a big difference to how hot a street is, as can adding vegetation and water to reduce the urban heat island effect.

These low-cost alterations are essential in developing countries nearer the equator where already intense heat is becoming more brutal. Eugenia Kargbo, who last year was appointed chief heat officer of Freetown, Sierra Leone, introduced lightweight polycarbonate shades to cover outdoor market traders, and plans to map heat in the city in order to identify particularly hot areas.

Freetown mayor Yvonne Aki-Sawyerr says Kargbo’s appointment means there is “somebody with a focus on this subject”. But a lack of funding is a major hurdle to doing more than “quick wins”, and the mayor says the city has received little support from the government for battling heat.

In Athens, the mayor is also pushing incremental changes, encouraging citizens to create “green roofs” by growing plants on their homes, and creating a dozen tiny pocket parks dotted throughout the city. “We’re moving forward with a number of long-overdue interventions,” says Bakoyannis. “It’s about the sum of small things.” 

Yet, with congested roads and little green space in the city, he is aware of how much there is still to do. “I don’t feel that one can ever say that they’re doing enough [on climate],” he says. “It’s an ongoing battle . . . And to be very transparent, we have lost precious time.”

In the meantime, the city hopes to revive a piece of its past to help mitigate the scorching present: Athens’ underground aqueduct, which was completed in around 140AD and was a key water source for the centre of the city as late as the 1960s.

Eydap, the Athens Water Supply and Sewerage Company, hopes to resume the use of 20 wells in the city, and use the water for non-drinking purposes, such as irrigating newly planted trees. It estimates that the network renovation works will cost about €9mn, which it hopes EU structural and investment funds will pay for, and be completed by 2027.

The channel, which still has some original Roman tiling, is about 25km long and runs from a nearby mountainous region to the centre of Athens. Not many people know about the subterranean system, says Giorgos Sachinis, Eydap’s director of strategy and innovation, “but it is a symbol of resilient infrastructure”.