From satellites to city streets: what will it take to protect cities from extreme heat?
It brought together WMO, the Global Climate Observing System (GCOS) and the Group on Earth Observations (GEO) alongside climate scientists, public-health experts, satellite agencies, urban planners and private-sector technology providers - a deliberately broad mix, reflecting how many actors already work on urban heat.
Many tools already exist to help cities deal with extreme heat, from heat-risk maps and health impact models to planning and investment tools. The challenge today is no longer creating new tools, but understanding which ones work best in different contexts and how they can be adapted and scaled from one city to another.
This is exactly the question iClimateAction set out to explore through its workshop. Bringing together experts and practitioners, the initiative took a first step towards assessing existing approaches and identifying what is needed to build a future Global Heat Resilience Service (GHRS). The goal is to help cities around the world access practical, reliable information and choose the most suitable solutions for their specific needs.
As “Eleni Myrivili, Global Chief Heat Officer at UNEP, put it: "Cities are no longer asking us to prove that heat is a problem. They're asking us to help them decide what to do on Monday morning." Her message reflects a growing reality. Cities already understand the risks posed by extreme heat. What they need now are actionable services that turn climate data into clear guidance for decision-making. By connecting climate observations, expertise and proven methodologies, iClimateAction aims to help bridge that gap between knowledge and action.
The underlying difficulty is one of scale. Global observing systems are very good at tracking heat at planetary and continental level, but cities experience it street by street. A dense district with little vegetation can stay dangerously hot through the night while a greener neighbourhood nearby cools down. Exposure varies just as sharply with age, income, housing quality, and access to shade and healthcare.
Different decisions need different information. A city planner may need detail at the level of individual streets or buildings; a health authority may need to anticipate hospital pressure several days before a heatwave peaks; emergency services may need to know where the most vulnerable people are concentrated.
The projects on show during the workshop made the range concrete. Examples included work linking heat to health impacts in cities such as Lisbon and Copenhagen, tools to help emergency services prepare for heatwaves in Milan, heat-risk assessment tools being piloted in Brazilian, Indian, and Chinese cities and community heat-mapping initiatives that capture local conditions on the ground. Other projects focused on helping cities identify the neighbourhoods most at risk, while some examined the economic consequences of extreme heat, from lost productivity to disruptions to infrastructure and services.
Across these examples a consistent message emerged: the bottleneck is rarely a shortage of data alone. Satellite and ground-based observations - including the Essential Climate Variables maintained through GCOS - are the foundation. They provide the baseline climate record, feed the models, and anchor validation. But foundations are not decisions. Climate and Earth-observation data only become actionable once they are integrated with other layers - where people live, who is most vulnerable, and the condition of housing, health systems and infrastructure. For cities, the real value lies not in individual datasets, but in combining them to generate insights that support practical decisions.
The discussions were also frank about technical limits. Participants noted that not all heat data tells the same story. Information collected from satellites is extremely valuable, but it does not always reflect the conditions people experience at street level or inside buildings. Equally, heat affects cities differently, depending on regional climate, urban infrastructure, and socio-economic characteristics making it difficult to apply the same risk thresholds everywhere.
Several participants stressed that many cities, particularly in the Global South, still lack reliable local monitoring, and that sophisticated tools can be hard for under-resourced authorities to run. One practical idea was a tiered, use-case-driven approach: a minimum viable analysis built on basic heat indicators and globally available population and built-environment data where local data is scarce, with enhanced layers - local observations, health data, validated thresholds - added where they exist. The aim is global coverage without pretending that every method is equally accurate or ready for operational use.
Perhaps the strongest conclusion was that cities need more local observations and measurements, collected where people actually live, work and move, if heat risks are to be understood accurately and translated into effective action. WMO’s contribution lies in the standards it sets for National Meteorological and Hydrological Services rather than in running services directly. Together, GEO, WMO and GCOS ensure that organisations use compatible methods and work towards shared goals, making it easier to coordinate investments across the public, private and civil society sectors. tNo single model will solve urban heat everywhere - cities differ too much in their infrastructure, data and governance. What the Geneva workshop pointed to instead is a clearer role for a global service like GHRS: not another platform, but a way to assess existing methods, match them to the decisions they can support, and be honest about what each one requires and where it should not be relied on. That assessment is the next phase of iClimateAction's work.
In the coming months, the team will conduct a structured feasibility study - combining expert interviews, stakeholder consultations and technical review - to determine which heat-resilience approaches are ready to scale, which need further development, and where the critical gaps lie.
iClimateAction is a Horizon Europe project bringing GEO, WMO and GCOS together to strengthen the Essential Climate Variables data chain from science to services. For more information, visit the iClimateAction website.
