The silent killer cities aren't ready for

Andy Deacon, Co-Managing Director of Global Covenant of Mayors for Climate and Energy (GCoM)

How does GCoM help cities fight extreme heat?

Most cities still lack localized heat-risk data that is sufficiently robust to spur action. Better data can reveal where heat poses the greatest danger—especially in low-income communities—and help cities direct investment toward climate finance, early-warning systems, and adaptation measures.

The Global Covenant of Mayors (GCoM) helps cities take meaningful climate action by providing the data, tools, and technical support they need to plan, finance, and implement adaptation and emissions-reduction strategies. We also connect cities with national governments and global partners so that local climate plans are backed by aligned policies and real funding.

Which cities worldwide are most at risk from urban heat, and why?

Cities close to the equator face the highest temperatures for the longest periods of time. Even modest warming from climate change can threaten health and infrastructure.

Global warming is intensifying heatwaves. In the past decade, some tropical cities have already experienced more than 100 additional extreme-heat days per year.

In reality, every city is at risk because dense construction amplifies the Urban Heat Island effect. This is especially pronounced in fast-growing equatorial cities. Studies in Quito, Ecuador, for example, show that some districts have warmed at twice the global urban warming trend.

Can cities like Quito cope with rising heat simply by installing more air conditioning?

We need to rethink how we design cities so they don’t fall into the vicious cycle of ever-increasing air-conditioning dependence.

Working with UN-Habitat and the UN Environment Program (UNEP), we’re promoting climate-sensitive design principles in urban planning, ranging from energy-efficient building codes and thermal-performance standards to zoning and land-use regulations. We also recommend public-space design guidelines that integrate nature, water, shade, and cool materials into the streetscape.

Urban nature and biodiversity are among our best defenses against heat.

What role is technology playing in fighting urban heat?

Technology is essential because it provides the data and analytical tools cities need to build an evidence base for action.

It begins with smart sensors and geospatial data, which cities use to map heat islands and conduct detailed Climate Risk and Vulnerability Assessments (CRVAs). We work closely with the World Geospatial Industry Council (WGIC) to improve access to this data.

AI and machine learning analyze these datasets and generate predictive models. For instance, a collaboration between C40 Cities and IBM—supported by GCoM and the Group on Earth Observations (GEO)—is developing an AI-powered tool to help cities assess risks related to extreme heat and the Urban Heat Island effect.

This analysis informs the implementation of practical solutions, from innovative materials and energy-saving building designs to nature-based solutions, green infrastructure, and tree-planting programs.

Technology also allows cities to test interventions virtually. Digital twins and 3D models simulate the impact of adaptation strategies before they are built. Geospatial tools help cities track progress, refine policies, and measure effectiveness.

Where are these technologies being used now?

I can cite several cases:

London and Medellín use networks of temperature and air-quality sensors mounted on light poles and waste-collection trucks. These provide real-time, hyper-local data to identify “hotspots” and guide decisions on cooling centers or mobile shading.

In South Africa, cities such as Tshwane, Cape Town, and Buffalo City deploy sensor networks—often attached to passenger cars—in a citizen-science approach that generates high-resolution, street-level data for more equitable heat-action planning.

Ahmedabad, India—whose mayor, Pratibhaben Jain, sits on the GCoM Board—is another pioneer. The city has adopted cool pavements and roofs, and installed reflective surfaces in public spaces.

To reduce fossil-fuel use, Valladolid, Spain has expanded a city-wide heat network in which a central plant distributes hot water to buildings across the city. The heat comes from power plants, waste-incineration facilities, geothermal wells, or even waste heat from data centers. The network now spans 200 km of pipes and serves more than 65,000 homes.

With rising heat and rapid urbanization happening simultaneously, how prepared are cities, and what support do they need?

This is one of the most significant challenges facing mayors today. We need a collective effort—what we call a Mutirão Global—to help cities protect lives and livelihoods as pressures increase.

We support the Beat the Heat flagship initiative designed by the Brazilian COP30 Presidency and UNEP. It calls on governments, big tech, financial institutions, and private-sector actors to help meet cities’ heat-resilience needs: assessing heat risks, developing action plans, cooling cities primarily through greening, and adopting low-GWP, high-efficiency cooling technologies in public buildings.

What worries you, and what gives you hope?

CO₂ and other global-warming emissions are still rising. The biggest barrier to climate action remains our dependence on fossil fuels, and the political and economic interests that perpetuate that dependence. Other challenges include insufficient funding for cities, geopolitical conflict, misinformation, and institutional inertia.

What gives me hope is that more mayors, policymakers, and communities are recognizing the risks and are actively experimenting with adaptation and resilience solutions.

We’re seeing growing demand for green infrastructure (trees, green roofs), nature-based solutions, reflective surfaces (cool roofs and pavements), data-driven analysis and mapping tools, and resilient urban design—from sponge-city approaches to heat-proof building codes and smart-energy systems.