Cooler Cities: Tackling Urban Heat

 

As our cities grow larger and denser, a quiet but powerful climate phenomenon is becoming increasingly visible: the urban heat island effect. Have you ever noticed how the city center feels hotter than nearby parks or the countryside? That's no coincidence. Urban heat islands (UHIs) are areas where the temperature is consistently higher than in surrounding rural or natural landscapes. While this might seem like a mere nuisance in summer, the implications are far-reaching: from increased air pollution and health risks to higher energy consumption and impacts on local climate resilience. 

The core reason behind the UHI effect lies in surface materials and the structure of the built environment. Cities are dominated by hard, dark surfaces such as asphalt, concrete, and brick, all of which have low albedo, meaning they absorb more solar energy rather than reflecting it. This absorbed heat is then slowly released as longwave thermal radiation, particularly at night, which prevents cities from cooling down efficiently.

Large cities may actually receive less incoming solar radiation than nearby rural areas due to pollution, yet they emit more heat because of their high surface temperatures. So it's not only about what comes in, but also what stays trapped. Dense urban development also disrupts natural air circulation. Tall buildings and narrow streets can block airflow, further intensifying heat accumulation. The combination of poor air movement, heat-retaining materials, and limited vegetation creates a feedback loop that reinforces the UHI effect. 

Landscape architects have a unique position when it comes to addressing urban heat. Our work often covers larger surface areas than traditional architecture, focusing on public and private outdoor spaces that significantly influence local microclimates. Choosing the right surface materials isn't just a matter of style or function, it's a climate strategy. In Finland, urban design often favors open views, sometimes limiting vegetation. But increasing green coverage, using permeable materials, and integrating shade trees can make cities cooler and more comfortable. Green roofs, natural water features, and stormwater wetlands are also effective tools, offering climate regulation and biodiversity benefits especially in dense urban areas. By rethinking surface design, landscape architects can enhance both urban livability and climate resilience. 

                                                       Illustration: Sarah Grillo/Axios

While urban heat islands pose real challenges, they also offer design opportunities — especially in northern climates like Finland. In cities such as Turku, slightly higher inner-city temperatures may reduce heating needs in winter and enable new planting possibilities. Compact urban areas can be envisioned to function like forests —spaces where elements protect and support each other. For landscape architects, this means designing with climate in mind, choosing materials and solutions that reflect, cool, and regenerate. 

Urban heat isn't inevitable —it's a result of design choices. Every paved surface, planted area, and design decision shapes our urban climate. By embedding climate-smart thinking into planning, we can build cities that are cooler, greener, and more resilient. 

Let's start shaping better, cooler cities together. Whether you're a designer, urban planner, student, or simply someone who cares about the future of our urban spaces, your perspective matters. How do you see the role of materials and green infrastructure in your own city? Feel free to share your thoughts in the comments below. 

Best, 

Emma