As record-breaking heat becomes increasingly common worldwide, more than 1.7 billion people face growing health and safety risks, according to the European Commission’s Joint Research Centre (JRC). Their data shows that half of the world’s cities have experienced rising heat exposure over the past four decades bringing mounting challenges for public health, productivity, and urban infrastructure.
A recent study published in The Lancet by the EARLY-ADAPT Joint Research Centre project reveals that over 4% of summer mortality in European cities can be linked directly to Urban Heat Islands (UHIs) localized zones where urban surfaces amplify heat. These hotspots are a result of construction replacing natural landscapes, altering surface properties and often trapping pollutants.
To tackle these challenges head-on, the CityCLIM project has developed a range of climate services using cutting-edge data science and satellite technology. “CityCLIM brought together diverse data sources to support mitigation and adaptation strategies for UHIs and climate hazards,” explains project coordinator Stephan Holsten of Germany’s OHB System.
From Data to Action in Europe’s Urban Heat Hotspots
Pilot studies were launched in Karlsruhe, Luxembourg, Thessaloniki, and Valencia cities selected for their distinct climates and urban designs. The project combined data from professional sensor stations, citizen science inputs (like mobile sensors on bikes), and Earth Observation satellites. Together, these painted a detailed picture of local temperatures, humidity, pollution levels, and vegetation coverage.
This was paired with an advanced 100-metre resolution urban weather model, which provided precise forecasts and helped simulate climate scenarios in dense city areas. All insights were integrated into a cloud-based climate platform, accessible to residents and city planners alike.
Tools to Empower Citizens and Guide City Planners
One of CityCLIM’s key outcomes is the Heat Island Identification Service a tool that uses improved weather models to predict extreme temperature zones across a city. This allows vulnerable residents to avoid hotspots and plan better during heatwaves.
For city administrations, a Heat Island Simulation and Mitigation Service was created. This tool lets users virtually redesign urban features, such as replacing concrete with greenery, and immediately see how the change affects urban temperatures. It’s a game-changing way to test ideas before breaking ground.
Holsten emphasizes that these tools were developed with real city needs in mind, ensuring they are practical, scalable, and transferable to other urban environments worldwide. “CityCLIM succeeded in building smart, responsive tools that cities can rely on to fight heat,” he says proudly.
As heatwaves become more frequent and dangerous, the CityCLIM model could soon become essential for climate-resilient city planning, offering a new standard for how cities around the globe prepare for a warming world.