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’ ‘liveability’, 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 behaviours 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 single body or choice of tactic can address and solve urban heating. 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 Issues 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 neighbourhoods and districts are contributing to the problem. This is where our urban heat mapping service becomes essential.

Publication

Urban Heat Snapshot

Our Urban Heat Snapshot reveals how the urban heat island (UHI) effect is pushing up temperatures in cities like London, Madrid, Mumbai and Los Angeles.

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

This kind of initial town- or city-wide baseline analysis is critical. For London, our work had three main goals. First, to identify which neighbourhoods comprised densities of property types that are most vulnerable to heat risks; second, which neighbourhoods’ 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 bodies 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 programme of interventions. 

Data and modelling only gets us so far. It’s important to back up our data analysis with local experience and personal testimony, understanding the population’s lived experience on the ground. This produces 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 prioritise 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 prioritise air flow 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 localised scale. We are often called on to help building and estate owners to explore mitigations that can reduce the temperature impacts faced by their buildings or estates. Working with developers and owners, we explore the most effective combination of design interventions for tenants and users, 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 interrogate large data sets 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 workable solutions.

Find out more about UHeat

Invest and improve blue and green infrastructure

Some of the most effective ideas for tackling climate change are ones we gain from nature itself. What we now call blue green infrastructure simply means refocusing on how we retain and encourage waterways, parkland and other green spaces within our urbanised 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 carried out some powerful 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 an issue that demands shared solutions and equitable treatment as our towns and cities respond to this aspect of the climate change challenge. Only addressing the issue partially, to the benefit of certain groups, would fall short of what we should be aiming for: successful and meaningful sustainable development. For strategists and planners, this means ensuring that heat action plans contain a reckoning with how the issue affects the entire community – in terms of public health as well as the social and economic implications – and ensuring that these factors shape the solutions that follow.