A Tale of Two (climate) Cities
Every city has a climate plan. The harder question, the one most plans quietly avoid, is whether it will work. Naples and Granollers decided to find out.
Two cities, separated by the length of the Mediterranean coast, and seemingly worlds apart. Naples: ancient, dense, sun-baked, sprawling across a coastline caught between volcanic geology and rising seas. Granollers: compact, industrious, tucked into a river valley thirty kilometres from Barcelona, where the Congost has flooded before and will flood again. Different in almost every way. Alike in what they face.
Both cities are already living with a changing climate. Heat waves that arrive earlier and linger longer. Rain that falls harder and drains more slowly. The slow, relentless pressure of rising seas. And somewhere beneath all of it, the knowledge that the choices made in the next decade will shape what their streets, their homes, and their communities look like for generations. Neither city is standing still. Both have plans, commitments, and genuine ambition. What they needed was clear numbers.
Putting the plans to the test
KNOWING brought together researchers from across Europe to work closely with local authorities, planners, and residents to develop what we call Climate Mitigation Pathways: integrated roadmaps that treat emission reductions and climate adaptation not as separate agendas, but as two sides of the same challenge. Using interconnected models covering energy, transport, flooding, urban heat, and public behaviour, the team put both cities’ plans through a rigorous, unsentimental stress test. The findings are neither purely reassuring nor purely alarming. They are something more useful: clear.
What the numbers revealed
For Naples, the science confirms that the city’s vision of greening its streets and waterways can make a genuine difference, particularly in the battle against urban heat. The energy transition emerges as a powerful lever, with substantial untapped potential in renewables and geothermal energy pointing toward a credible path to deep decarbonisation. And yet the models also show where ambition outruns what nature-based solutions alone can deliver, especially on flooding, where more structural interventions will be needed alongside the green ones.
For Granollers, the plan to re-naturalise the banks of the Congost, reconnecting the river with the city’s green network, holds real promise for cooling the urban fabric. The science is honest about what this can and cannot achieve against flood risk, and it raises a question that technical models alone cannot fully answer: how will people actually respond? Public behaviour, it turns out, is not a footnote. It is part of the pathway.
Perhaps the starkest finding for both of them concerns time. Delaying action forfeits options. Every year of inaction narrows the window and raises the eventual cost of catching up.
From two cities to many
The full results are on their way to peer-reviewed publication. But what these two cities have already demonstrated is something worth naming: that looking clearly at a difficult situation, without flinching from what the numbers say, is not a counsel of despair. It is the precondition for genuine hope.
Cities across Europe face versions of the same reckoning. The pathways developed for Naples and Granollers are designed to travel. Transferable frameworks that other cities can build on as they navigate their own climate futures. www.knowing-climate.eu
About KNOWING
KNOWING is a Horizon Europe project that develops tools, models and participatory formats to support climate-transformation. By combining scientific analysis with local knowledge and stakeholder input, the project supports regions and sectors to understand climate risks, assess options, and design effective, inclusive pathways for change.