Urban areas across the Western Balkans have seen a surge in heat-related stressors—mainly heightened temperatures and intensified droughts—that will have serious effects on regional stability and productivity.

In what is known as the urban heat island effect, the urban built environment in the region is often characterized by nonreflective and heat absorbing surfaces, limited airflow, and lack of vegetation, all of which trap the heat and raise local temperatures relative to surrounding areas. This phenomenon is exacerbated by the extensive use of air conditioning and motorized transportation, which also raise temperatures.

Yet urban areas in the Western Balkans typically lack sufficient data on the effects of heat-related stressors at the local level. The end result is that public authorities and local communities have limited information to battle the effects of extreme urban heat.

In response to these challenges, GFDRR has supported a collaborative effort by local climate researchers and community volunteers to map the incidence of urban heat across cities in Albania (Tirana, Shkodra, and Vlorë) and Bosnia and Herzegovina (Sarajevo and Mostar). This effort is being coled by the City Resilience Program (CRP) and the Digital Earth Partnership, both of which are partnerships between GFDRR and the World Bank.

With the support of GFDRR, researchers and volunteers, armed with heat sensors mounted to the windows of their vehicles and navigation software, gathered detailed data on temperature, humidity, and particulate matter in the morning, afternoon, and evening. As they drove through their cities, thousands of measurements per trip were collected at a rate of one sample per second. Between crossings, they photographed selected locations with thermal cameras to investigate surface temperatures and record observations of the built environment and how these spaces were being used by people in these communities. The variety of measurements collected simultaneously across the cities revealed a detailed picture of how urban heat exposure differs depending on where people live, work, and travel.

A key finding from these efforts is that the urban heat island effects were much stronger at night. The pronounced heat island effect at night is likely because the heat stored in building materials is gradually released after sunset. At the same time, the researchers and volunteers found that the urban heat island effects were stronger in some parts of the cities than others. Temperatures could vary by over 8°C across different parts of the city: 8.2°C in Mostar, 7.4°C in Sarajevo, 6.5°C in Shkodra, 6.4°C in Vlorë, and 4.3°C in Tirana.

Already, these findings are beginning to inform efforts by cities across the Western Balkans to tackle extreme heat. For example, the variations in urban heat island effects within cities seemed in part explained by the relative lack of urban greenery in some areas. Accordingly, this would seem to underscore the importance of protecting and expanding green spaces. All the cities analyzed generally have green areas concentrated in the outskirts or only one side of the city.

In addition, the findings have also contributed to the World Bank’s Western Balkans 6 Country Climate and Development Report, which lays out a strategic framework to inform investments by the Bank and other development partners toward climate adaptation and mitigation across the region for the next 5–10 years.

Looking ahead, the hope is that more city planners, researchers, and even residents will draw on the rich data gathered, which has since been made available in an open access database, to further inform efforts to tackle extreme heat and, by extension, build a more resilient future for communities across the Western Balkans.

“Projects such as this in Mostar hold significant importance, especially considering Mostar’s status as one of the warmest cities in the entire region. This is a commendable study that provides invaluable data to the city of Mostar, considering the ongoing climate change that we are witnessing daily. It will help us steer activities in Mostar in the right direction and adequately spend the city’s funds.”

—Dr. Sc. Mario Kordić, Mayor of Mostar