The UK is facing its first heatwave of the summer, and while many will be basking in the hot weather it is also a warning of challenges to come, particularly for those who live and work in our biggest cities.
Extended periods of high temperatures are becoming more frequent and intense all over the world because of climate change, and we are learning just how much our metropolitan areas struggle to cope with heat.
Our cities were designed for cooler climates, but as temperatures climb with rising greenhouse gas levels they need to be transformed to prevent hot weather from threatening lives and livelihoods.
Cities are particularly at risk during heatwaves because of the urban heat island effect. The dark-coloured, human-made surfaces of buildings and roads tend to absorb sunlight and trap heat. As a result, the temperature of urban areas is often several degrees higher than the surrounding countryside. The very fabric of our urban areas makes them prone to overheating.
And the high temperatures can be deadly, particularly for people with underlying health conditions, such as respiratory illness. Cities can also become suffocating because bright sunlight often leads to higher levels of air pollution. And sweltering offices make workers less productive, creating a hit to the economy.
We cannot simply bulldoze our cities and build them again in a way that is better suited to our warming climate, so we have to retrofit and adapt them.
Although it might seem tempting to rely on air conditioning, this would lead to huge increases in electricity use. Large, hot cities, even in rich countries such as the US, can suffer blackouts in the summer owing to the power load as homes and offices try to maintain comfortable room temperature. And air conditioning can be prohibitively expensive for people on lower incomes to install and operate, exacerbating the climate injustice between the haves and have-nots.
And of course, air conditioning units simply transfer heat from inside buildings into the surrounding area, making the outdoors even hotter. We have to take a different approach.
Instead of desperately removing excess heat from our city buildings, we will need to prevent the sun’s rays from creating the problem in the first place. Offices and homes will need tinted glass, blinds or shutters fitted to keep out sunlight. And white roofs should become standard to reflect the sun’s rays rather than absorb them.
New and retrofitted old buildings will need to be designed to increase ventilation with natural flows of air to keep internal temperatures down. These are features of well-designed cities in hot countries, which we must adopt. We need building regulations that force developers to design buildings so that they do not overheat.
Public transport systems, particularly underground trains, will need to be fitted with ventilation and air conditioning. The London Underground already encourages passengers to carry water during journeys on hot days to avoid dehydration, but the heat can also lead to mechanical and electrical failures on the network.
Road surfaces will need to be treated to prevent them melting, and train tracks and overhead cables will need to be made of materials that do not expand and change shape too much in sweltering temperatures. In recent summers we have already seen the chaos that high temperatures cause to our rail system.
But people who live or work in cities also need to change their behaviour to protect themselves from hot and humid weather. Once temperatures exceed 40C (104F) even fit and healthy people can be at risk if they exert themselves too much. So we have to get used to simply avoiding direct heat at certain times. More cities will need to follow the example of those closer to the equator by banning construction and other strenuous work during the middle of summer days. It is high time that Englishmen left the mad dogs alone to brave the midday sun.
London is already following many other cities by setting up “cool spaces” where the capital’s residents can find respite during hot weather. And it is also planting more trees help to filter out sunlight and stop pavements from becoming unbearably hot.
Our cities should also develop stronger social support systems so that help and advice is offered to those most at risk from heat, particularly older people. Care homes must be a priority for measures to counteract overheating.
But most of all, our cities need integrated heat risk-management strategies, which bring together all the many public- and private-sector players, at both national and local levels. They may need to follow the example set by Miami, Phoenix and Athens to appoint chief heat officers to coordinate action.
We will all need to change our attitude to summers. Yes, they are opportunities to enjoy the hot weather. But unless we adapt to our warming climate, our cities will become ever more unbearable and perhaps even inhospitable.
Bob Ward is deputy chair of the London Climate Change Partnership
