How do we protect our cities from rising temperatures?

Rising temperatures present different countries and communities with a range of problems to solve – from public health, areas' livability, to infrastructure and economic challenges.

In the last century, as towns and cities have grown, urban heat islands have proliferated, with the effects magnified by continued growth in CO₂ emissions. As shown by recent events like the 2024 LA wildfires, unusual climate patterns lead to unprecedented severe weather, making the need for climate-resilient planning and design measures ever more vital.

Urban cooling – as part of broader climate adaptation and resilience-building – is now a vital priority for cities worldwide, but many areas lack the specialist insight to tackle the complex problem of extreme heat. Rising temperatures are a shared problem that everyone in the community faces, so solutions across planning, design, operational practices and day-to-day behaviors must work for all.

In recent years, Arup's climate experts, urban planners and building engineers have been helping cities and governments to navigate changing climate conditions and extreme weather at a number of different levels. It's clear to us that no one entity or approach can address and solve urban heat. It requires engagement from the whole community and city-specific insights. It will take urgent and bold changes to urban planning and building policy and construction standards. Fundamentally, it requires an openness to new ideas from asset owners, planners and developers. In this issue article, we explore some of the solutions and approaches that work best.

1. Identify and map the heat issues your city faces

Over time we can all sense when our home, town or city seems hotter and less bearable during warmer seasons. But for decision makers to act, we need a more granular definition of how the city’s individual neighborhoods and districts are contributing to the problem. This is where our urban heat mapping service becomes essential.

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Urban Heat Snapshot

After the UK’s 2022 heat wave, we conducted a comprehensive analysis of London’s vulnerability to heat impacts for the Greater London Authority and Mayor of London.

This kind of initial citywide baseline analysis is critical. For London, our work had three main goals. First, to identify which neighborhoods comprised densities of property types that are most vulnerable to heat risks; second, which neighborhoods’ ambient temperatures had already risen thanks to urban heat island effects; and third, which residential areas faced the greatest impacts from extreme heat, given the nature and underlying characteristics of their populations.

2. Develop a workable cooling strategy

With the analysis complete, we sit down with city authorities, with their Chief Heat Officers, and other agencies to identify local factors that are leading to heat gain. This work is always driven by local factors, and needs to amount to a practical, cost-effective and timely program of interventions.

Data and modeling only gets us so far. It’s important to support our data analysis with local experience and personal testimony, understanding the population’s lived experience on the ground. This yields a richer picture of the impacts communities have felt, and insights into workable, local solutions that will gain support.

With this analysis and exploration completed, we can develop valuable advice for stakeholders, such as local authorities, to consider how they can prioritize adaptation measures or retrofitting. These vary but could include the use of blue-green infrastructure, green building envelopes, cool roofs and other passive solutions. Planning solutions for new districts can and should prioritize airflow between buildings, again driven by careful analysis of the local climate conditions and historic urban development patterns.

3. Use design to reduce temperatures

Heat is an inherently diffuse issue, one that must be tackled in a strategic, coordinated way while also implementing design and engineering solutions at the smaller, more localized scale. We are often called on to help property owners to explore mitigations that can reduce the temperature impacts faced by their buildings or properties. Working with developers and owners, we explore the most effective combination of design interventions for tenants and occupants, including options like solar PV shading, ventilated façades, glazing solutions or alternative building orientations.

Powerful digital analytics

The ability of ever advancing artificial intelligence and machine learning models to analyze large datasets and provide insights is reshaping how we approach urban cooling. We developed our heat analysis and mapping tool, UHeat, to identify local temperature data and the relevant urban factors driving and exacerbating the problem. UHeat uses the latest in machine learning analysis of satellite imagery to identify and tag structures and materials, locate heat sources and provide insights into feasible solutions.

Find out more about UHeat

Invest and improve green infrastructure

Some of the most effective ideas for tackling climate change are ones we gain from nature itself. What we now call green infrastructure simply means refocusing on how we retain and encourage waterways, parks and other green spaces within our urbanized environment. Many cities have discovered that tree planting is a cost-effective way to lower temperatures and can become a valuable intervention in a wider programme of urban cooling. Water has another powerful effect in reducing temperatures and with careful and creative planning waterways, fountains, and other bodies can be introduced within the urban fabric.

4. Recognise heat as a vital social issue

Extremes of temperature affect everyone’s personal lives and shared experiences. It’s an inherently social issue that communities face in different ways. For those wealthy enough to run air conditioners, the issue is lighter than those in areas left to fend for themselves as temperatures rise. In 2023-4 we conducted research on how the issue highlights inequities in Los Angeles, and looked at how solutions should factor this aspect in future.

Article

Urban extreme heat planning: it takes a city

Cities are becoming hotter, yet a majority are not prepared to respond. Embedding heat action plans throughout all levels of city government is one way forward.

Like air pollution, heat is a problem that demands shared solutions and fair treatment as our towns and cities respond to this aspect of the climate change challenge. Only addressing the problem partially, to the benefit of certain groups, would fall short of what we should be aiming for: successful and significant sustainable development. For planners and planners, this means ensuring that heat wave action plans contain an understanding with how the problem impacts the entire neighborhood – in terms of public health as well as the social and economic implications – and ensuring that these factors inform the solutions that follow.