Building urban heat resilience into our cities

Europe is experiencing temperatures rising at twice the global average rate, and heat-related mortality has increased around 30% in the past 20 years. The urban heat island effect worsens this, causing cities to face even higher temperatures than rural areas. This poses risks to public health, infrastructure and the economy. Despite these challenges, heat-related concerns are often overlooked in cities’ climate plans, especially for vulnerable populations.

Extreme heat events will only increase in intensity, frequency and duration in the future due to anthropogenic climate change. Impacts will be felt across Europe, and cities in particular will be vulnerable due to their agglomeration of people, infrastructure, and economic activity. As we face such events of higher intensity and frequency and live in increasingly dense urban neighbourhoods, we must ask ourselves how to best design our living environments for the most vulnerable citizens – our children and the elderly.

While cities recognise the health risks of heatwaves, they often fail to incorporate equitable resource distribution and protection for marginalised communities into urban resilience planning. This is compounded by a lack of detailed data and vulnerability mapping across cities, hindering monitoring and evaluation of existing adaptation policies.

To effectively tackle heatwaves, clear governance, innovation, and co-creation are crucial, along with long-term visions and adaptable strategies. Collaborative governance, public awareness and community empowerment are key for effective adaptation. Action on blue-green infrastructure is also vital, ensuring solutions meet community needs and have positive impacts.

Impacts on health – and life

European cities are projected to witness a rise in both the number of heatwave days per year and the maximum heatwave temperature. High-impact scenarios suggest that 72% of European cities will experience a temperature increase of at least 10° during heatwaves.* And during the summer of 2022, more than 61,000 people died because of Europe’s record-shattering heat wave, according to scientists.&

Extreme heat events are linked to a multitude of health impacts: dehydration, heatstroke and exhaustion, increases in incidence of disease and increases in premature death. The elderly, infants and young children, those with pre-existing health problems and those in hospital or bedridden are most at risk.

Certain groups in cities are more vulnerable to heatwaves than others, such as young children and older people. While the proportion of younger people in Europe is not set to change, Europe is getting older, and the elderly are particularly at risk. In Europe, the number of people over 65 is rapidly increasing, with those over 80 expected to more than double from 5.6% in 2018 to 12% by 2060. Cities will face multiple shocks and stresses in the future, with the vulnerable usually paying the highest price.

While these groups are physiologically more sensitive to heat, how people subjectively experience heat is also important and depends on a complex interaction of many factors:

1. Physiological. Previous long periods of hot weather can result in physical acclimatisation, reducing the negative impact on the human body.
2. Local climate. Humidity, air temperature, shading and windchill all impact on how heat is experienced.
3. Socio-economic. Being socio-economically disadvantaged affects your experience of extreme heat – for example, due to the quality of available housing, the availability of affordable mitigation measures like air conditioning, and proximity to green spaces.
4. Psychological. Spending time in urban greenery can improve perceived well-being, alleviating the perception of thermal discomfort. While the proportion of younger people in Europe is not set to change, Europe is getting older, and the elderly are particularly at risk. In Europe, the number of people over 65 is rapidly increasing, with those over 80 expected to more than double from 5.6% in 2018 to 12% by 2060.

1. Invest in knowledge-building

Set long-term visions and short-term actions: Set long-term goals for heat resilience, aiming towards 2100, and then work backward to trace the steps needed to achieve those goals. This helps clarify the necessary goals and actions for the medium and the short term.

Make action plans and set priorities: For policymakers and urban practitioners, it is imperative to prioritise the development of comprehensive heatwave response strategies. These strategies should be informed by robust empirical evidence and grounded in principles of climate equality, like accessibility and fair distribution of resources.

Test, monitor, assess and adjust: Approach heat management in the same proactive manner as water management – through testing, adaptation and modulation. When implementing blue-green solutions to combat heat, it is crucial to conduct thorough testing and follow-up assessments to ensure that these solutions effectively meet the needs of the community and make the desired positive impact.

2. Innovate and optimise

AI, digital twins and IoT
– Develop advanced AI algorithms to predict and monitor heatwaves, allowing for early warnings and proactive planning.
– Implement smart infrastructure solutions, such as intelligent cooling systems and energy-efficient designs, to reduce the urban heat island effect and provide cooling in high-risk areas.
– Utilise digital twins of cities or specific regions to simulate and optimize urban planning strategies, including the placement of green spaces, shading structures, and cooling measures.
– Incorporate IoT sensors and data analytics to gather real-time information on temperature, humidity, and air quality, enabling targeted interventions and resource allocation during heatwaves.
– Enable and optimise the use of renewable energy sources and energy-efficient technologies to reduce heat-related energy consumption and greenhouse gas emissions

3. Develop ecological networks and cooling corridors

Develop urban cooling corridors: Create visions and plans to configure networks of open spaces at the city level, reinforcing existing landscape and green-blue structures, connecting the missing links and providing the framework to incrementally create cooling corridors at the city level that have high ecological value.

Create multifunctional open spaces: Many blue-green solutions can effectively manage both stormwater and heat. These solutions optimise land use efficiency and prioritise biodiversity and social sustainability.

Optimise building orientation: The orientation of buildings towards the outdoor environment is vital. Buildings can serve as a significant component of shading functionality

4. Upgrade systems and networks with nature-based solutions

Develop nature-based solutions: Improve existing mobility infrastructure through nature-based solutions. These are actions that protect, sustainably manage and restore natural or modified ecosystems in order to address societal challenges effectively and adaptively while providing human well-being and biodiversity benefits.

Define the role and goal of greenery: Set specific objectives and desired outcomes that greenery should achieve in the project, like improving air quality or providing recreational spaces by selecting appropriate plant species and implementing green infrastructure techniques, for instance. Identify the critical factors and requirements necessary for a successful implementation, such as site conditions and collaboration with stakeholders.

Optimise paved surfaces: Another multifunctional approach involves integrating heating adaptation with mobility strategies in cities. By reducing space for cars through measures like reducing lanes and implementing one-way streets, more space becomes available for greenery.

5. Increase building performance

Design high-performance buildings with advanced technology to remain functional even in extreme heat. Incorporate effective ventilation and cooling systems during construction. Engage with users to understand their needs. Consider ceiling height, awnings, blinds and operable windows to mitigate solar radiation and heat buildup.

Redesign building regulations: In the Nordic countries, today’s building regulations are designed to keep heat inside and cold outside. However, in light of the increasingly warmer climate, we need to rethink these regulations.

6. Co-create

Establish heatwave governance: Cities need to create crisis teams dedicated to managing heatwaves, mirroring the approach taken for heavy rainfall and floods.

Set cooperation frameworks: City networks offer significant benefits for climate adaptation and resilience. They facilitate city-to-city learning through the sharing of best practices and increase access to funding opportunities.

Raise awareness and involvement: Enhance public awareness, education and participation, cities can harness local knowledge, resources and creativity to develop more effective and inclusive climate adaptation measures.

Extend heatwave mapping: Mapping vulnerable groups in relation to heatwaves is crucial. In addition to geographic information systems (GIS), alternative data gathering methods such as citizen science can be leveraged. Citizen science provides precise data on fine-grained contexts and helps raise awareness and foster community engagement.

Co-create: Engage intended users in the design process. For instance, educators should be consulted when designing a preschool playground. It’s crucial to designate responsibility for playground upkeep upfront. Besides greenery, immediate shade solutions like pergolas or sunshades are vital, especially since newly planted trees take years to mature.

Empower communities: Proactive measures are crucial in helping vulnerable populations cope with extreme heat. Cities and organisations can engage with these groups to implement strategies, such as setting up cooling centres, providing multilingual heat safety information and offering assistance with utility bills or access to air conditioning units during heatwaves.

European cities are facing a pivotal moment in their approach to managing the increasing severity and frequency of heatwaves.

The case study cities in our Urban Insight report have taken some key steps in the right direction. They have emphasised nature-based solutions across green and blue infrastructure, integrating heatwave adaptation measures into planning legislation and conducting limited GIS mapping.

However, cities across Europe are still learning how to mitigate and adapt to the risks posed by heatwaves to residents, services and assets. Only a select number of cities have dedicated adaptation teams who have planned for heatwaves. This is particularly true for Northern European cities, where heatwaves are a relatively new and uncommon phenomenon.

Climate equality – data and vulnerability mapping needed

Beyond investment in green-blue infrastructure and technological innovation, there is an urgent need to pivot towards participatory policymaking informed by city-to-city learning and centred on those most affected by heat extremes.

This emerging challenge exposes significant gaps in urban heatwave adaptation policies, particularly with regards to vulnerable populations. While cities recognise the correlation between heatwaves and negative health outcomes, the concept of climate equality remains underrepresented in urban resilience planning.

This absence is exacerbated by granular data and vulnerability mapping across cities, with little to no monitoring and evaluation available for current adaptation policies across the board.

For policymakers and urban practitioners, it is imperative to prioritise the development of comprehensive heatwave-response strategies informed by robust empirical evidence and grounded in principles of climate equality, ensuring safety measures for especially vulnerable populations.

Resilience and governance

Resilience is a broad and contested concept, with each case study city offering a slightly different definition. The cities all had a common focus on adapting urban infrastructure to the changing climate. However, resilience and adaptation were not immediately and explicitly linked to vulnerable communities by all of them. Developing a holistic and nuanced understanding of resilience, in line with transformational adaptation, is essential to ensuring just and equitable responses to heatwaves.

Due to links to net zero, health and urban planning, resilience is a cross-departmental and cross-partner issue for cities that requires collaboration and leadership from multidisciplinary expert networks. Cities simply do not have the power to do everything themselves – they require collaboration and an evolution in governance models.

Financing presents a challenge, emphasising the need for cost-effective measures and innovation in business models to address heat-related issues effectively. In the face of accelerating polycrises, cities can design heatwave responses that are not only effective but equitable, ensuring that every resident can withstand the heat and thrive. Cities have the information and understanding needed for cooler, liveable cities. Now is the time to act and build the resilient cities of tomorrow, today.

*Guerreiro, S, B. et al. (2018). Future heat-waves, droughts and floods in 571 European cities. Environ Res, Lett, 13 034009. https://iopscience.iop.org/article/10.1088/1748-9326/aaaad3/meta
**Harvey, C. et al. (2023). 60,000 People Died from Blistering European Heat Waves, New Analysis Finds. SCIAM. https://www.scientificamerican.com/article/60-000-people-died-from-blistering-european-heat-waves-new-analysis-finds/