Studying the socioeconomic roots of urban heat with Santamouris

Professor Mat Santamouris explains in this interview his recent research on how urban heat and social inequality intersect in London, Seoul, and Shenzhen. 

Santamouris is a leading expert in urban climate, sustainability, and environmental science, with a focus on the impacts of climate change in urban environments. He has conducted extensive research on urban heat islands, socio-economic disparities, and green infrastructure in cities around the world, contributing to numerous publications in this field.

His most recent studies reveal that London's low-income areas face more severe heat challenges compared to those in Seoul and Shenzhen, largely due to historical planning and fewer green spaces.  According to him, these insights underscore the need for urban policies that better address both environmental and social disparities.

Image: Prof. Santamouris / supplied

Architecture & Design: Your research highlights the link between income levels and urban heat intensity in London, Seoul, and Shenzhen. What were the most striking differences in how this relationship manifests across these cities?

Mat Santamouris: The existing literature is rich in studies performed in various USA cities showing that low income and vulnerable population lives in deprived areas suffering from significant overheating, low greenery levels, high pollution and inadequate infrastructure. Similar conditions are also observed in several European cities like London. However, in most of the Asian cities, the conditions are quite different. 

Although there is an important social stratification, the magnitude of the problem is less severe. This is because, the market forces and the social and economic inequalities observed in American cities and which have determined the local social, economic and environmental diversification, present different characteristics in the Asian cities and had much less significance through the history, contributing towards a higher social cohesion and decreased local discriminations.   

In London, lower-income populations experience greater urban heat island (UHI) effects compared to their wealthier counterparts. What urban planning or policy factors have contributed to this disparity?

In London, immigrants, minorities and vulnerable and low-income population were pushed to live in urban zones of lower economic value and financial cost. Low-income population has not the economic means to live in the expensive parts of the city and should settle in economically affordable neighbourhoods. In these low-cost urban zones, green infrastructure, heat sinks and efficient environmental systems are quite missing, while most of these neighbourhoods may suffer from very serious anthropogenic heat generated from the local industry or the traffic rising the magnitude of the local overheating and the pollution levels. 

This is not the case of the wealthier urban zones were the local green infrastructure; the landscape characteristics and the release of the anthropogenic heat is considerably reduced contributing towards a more sustainable local microclimate and environment.
  
Your study suggests that income has a weaker influence on urban heat exposure in Seoul and Shenzhen compared to London. Could you elaborate on the social and economic structures that contribute to this difference?

The environmental and overheating stratification and the heterogeneities observed in London and also in most of the US cities, reflect in a direct way the economic and social stratification in the local societies. 

The size of the low income group in the society including minorities, immigrants, unemployed people, non-skilled population and non-integrated households, is quite higher in London than in the specific Asian cities. Poverty is generating heterogenous social dynamics exerting serious pressures on land use policies, investments on environmental infrastructure and in conclusion on the social protection coverage in the city. 

To what extent do green infrastructure and blue-green interventions help mitigate UHI effects for vulnerable communities in these cities? Are there best practices that London could learn from Seoul and Shenzhen?

Green and blue infrastructure helps to decrease the local temperature, reduce the levels of atmospheric pollution and offer important social, economic and environmental advantages to the local population. I don’t believe that London must learn something from the Asian cities. 

The problem and its characteristics are well known but the economic priorities and the forces driving and determining the local policies in these cities incorporates at the end the serious inequalities as an integral and finally acceptable part of the city characteristics.   

Your findings indicate that historical development patterns play a role in shaping urban heat disparities. Can you provide specific examples of how city planning history in each city has influenced current UHI patterns?

Social tensions exerted at the city level and pressing needs for habitat, employment and surviving have partially determined the characteristics of the specific use of land by the various economic layers in the society. 

In cities with strong immigration, significant non-integrated minorities, rapid urbanisation, lack of social protection, weak employment structures, inadequate infrastructure, limited economic resources and forced economic transition, the social and economic pressures were enough strong to lead in the development of new residential areas located in unclaimed and low cost suburban areas without the necessary planning and with the sole objective to settle at any cost the tide of vulnerable and low income population arriving or already existing in the city.

Did your research identify any unexpected factors, beyond income and green space availability, that significantly impact urban heat exposure for vulnerable populations?

I believe that the characteristics of the existing situation in the cities are well understood and explained by the scientific community and especially by the local experts. What is interesting is the comparison between cities that magnifies the differences and permits to focus on the relative efficiency of the followed urban policies in the various parts of the world. 

Given that London appears to have a more pronounced income-UHI correlation, what policy interventions do you think could most effectively reduce heat-related inequalities in the city?

Decision makers have to understand that poor environmental quality in the deprived and low income urban zones has a very significant cost for the city and the country. It increases the energy consumption, and the cost of the required health services to support the local population, decreases the cognitive performance of the local kids, reduces the working time and efficiency and creates serious social problems. 

Policies aiming to improve the environmental, health and social conditions in these parts of the cities are finally investments providing serious economic, social and environmental benefits not only for the local population but for the whole city.  

Seoul and Shenzhen seem to have less pronounced UHI disparities based on income. Do you think their local policies and urban planning strategies could be successfully applied to cities in Europe and North America?

I don’t think so. The social, economic and environmental characteristics in most of the American and European cities are completely different than that of the Asian cities. Understanding of the social and environmental procedures helps for sure to improve our experience and knowledge but solutions are always city specific.

As urban populations continue to grow and climate change intensifies heat stress, what key recommendations would you offer to policymakers aiming to create more heat-resilient and socially equitable cities?

The combined impact of overpopulation and climate change can have disastrous effects in cities and especially in South East Asia. There is a risk, if not a certainty, that more than 1.5 billion people will live under extreme heat conditions that human never experienced in the past. 

Although the problem requires global solutions much above the city level, urban administrations can modulate and mitigate and why not counterbalance the negative impacts through the implementation of policies based on the principles of social equity, sustainability, resilience and fair economic development.

Looking ahead, do you plan to expand this research to other global cities? If so, which locations do you consider particularly important for further study, and why?

We are working on the characteristics of several other cities in Australia and Asia. In parallel, the research community is gradually increasing the knowledge on the topic by analysing new interesting data and socio-economic phenomena from several global cities.

Both studies were carried out together with Santamouris' Chinese and Korean colleagues: Sarath Raj, Lee Yerim, Geun Young Yun a, M. Santamouris : Contrasting urban heat disparities across income levels in Seoul and London, Sustainable Cities and Societies, 121 (2025) 106215 | Mingqian Li, Chunxiao Wang, YulianWu, M. Santamouris ShuaiLu: Assessing Spatial Inequities of Thermal Environment and Blue-Green Intervention for Vulnerable Populations in Dense Urban Areas, Urban Climate, Volume 59, February 2025, 102328.

Both studies can be found here and here. 

Image: ABBPhoto / Envato