At the height of summer, the air conditioner is your best friend. But what do you do when blistering hot summer days become more frequent and intense? That’s increasingly the case in many European and Central Asian cities.
The Urban Heat Island effect, or UHI, makes cities more vulnerable to heatwaves. Densely populated, built-up areas tend to be much warmer than their non-urban surroundings for several reasons. Cities have reduced air circulation and are often built with materials known to store heat easily. They also generally lack vegetation, and concentrate heat coming from buildings, factories, and vehicles.
Between 1950 and 2015, 27% of cities were warmer than the global average (about 0.6 degrees). Cluj, Romania, can be anywhere between 2-3 degrees warmer than its surrounding rural areas. The economic losses are staggering: heatwaves cost Cluj an estimated €2.5 million per day.
The human toll is even worse. Urban heat can cause dehydration, heat cramps, strokes, and even death. Between 1980 and 2018, heatwaves caused over two-thirds of all hazard-related casualties in the European Economic Area.
Severe heat makes vulnerable populations even more vulnerable. For example, residents with restricted movement cannot access parks or other areas with cooler temperatures. The poor are hit hardest because low-income neighborhoods are often densely constructed with few green spaces or water surfaces to help cool the area.
Fortunately, there are three ways to manage the impacts of urban heat.
First, a recent World Bank report supported by the Global Facility for Disaster Reduction and Recovery highlights the role of modeling in helping decisionmakers and urban planners better understand complex urban climate processes at different scales. Building-scale models reveal the energy balance of construction materials and heat fluxes, while micro-scale models inform building orientation. Other models can lead to better surface materials and vegetation choices, analyzing the interplay of soil, water bodies, and wind circulation.
Second, there is a wide range of measures—including “green” (i.e. parks), “blue” (i.e. fountains) and “white” (i.e. reflective roofs or roads), all of which can reduce urban heat. Many cities are adopting these measures to promote sustainable urban planning and climate change adaptation. Here are some examples:
- Green: In Poland—where towns suffer excessive evening heat over 80% of the time—the city of Białystok has implemented green bus stops to bring relief from the heat. Portugal’s Cascais is rehabilitating and creating “Green Corridors” to reduce vulnerability to floods and heat waves, and improve livability. In North Macedonia, the 2011 Heat-Health Action Plan includes the creation of green areas.
- Blue: Vienna uses a network of cool streets with water elements, and in Ober-Grafendorf, a “green street” proved a cost-efficient way to reduce local temperatures (by as much as 5 degrees) and local flooding. In the UK, Europe’s largest urban wetland near London combines water and recreation.
- White: An analysis of white roofs on a school and laboratory building in Greece showed an average decrease of indoor temperatures by 1.5-2 degrees, and a substantial decrease in surface temperatures. Worldwide use of reflective roofing could produce a cooling effect equivalent to offsetting 24 gigatons of carbon dioxide, or taking 300 million cars off the road for 20 years.
Source: World Bank.
Implementing green or white roofs, and adding water bodies can reduce urban heat load, contribute to health and well-being, and bring further benefits to the city.
Third, to save lives, it is critical to invest in emergency preparedness and public communication of risks. This includes public alerts, raising awareness, and taking targeted action during a heat wave. After the 2003 heatwave, France revised its heat health action plans and communication strategy, targeting the elderly and other vulnerable groups with specific measures for nursing homes and health facilities.
The WHO predicts a long and hot summer period in Europe. Cities need to take urgent action. Real-life experience shows that managing the risk of urban heat can be integrated into improved urban planning, disaster risk management, and climate change adaptation strategies.
Investing in mitigating and understanding urban heat effects, while making no-regret improvements to public health preparedness and response, can make cities more resilient and more livable for all residents.