The City of Light is turning to the waterways of the past to cool its future. Paris has officially adopted a canal-based cooling system, drawing direct inspiration from a pilot programme in London as European capitals scramble to adapt to a warming planet.
This week, Parisian authorities announced the deployment of a district cooling network that taps into the Canal de l’Ourcq, using its water as a heat sink for buildings along the Right Bank. The system, known as ‘Paris Climatique’, will provide low-carbon air conditioning to over 200 public buildings including hospitals, museums, and government offices. It mirrors the Thames Water Source Cooling project in London, which has been pumping water from the River Thames through heat exchangers since 2018.
Both cities are confronting a physiological limit. By mid-century, Paris is projected to experience heatwaves of 50 degrees Celsius. Air conditioning units, which expel hot air into the street, create urban heat islands and drive up electricity demand. Canal cooling is more efficient and has a lower carbon footprint: it uses the thermal mass of water to absorb heat, which is then dissipated elsewhere in the system.
The science is straightforward. Water holds four times as much heat as air. A volume of water passing through a building can absorb heat energy with negligible temperature rise. The warmed water is then cooled naturally in a dedicated lagoon or via cooling towers, before being recirculated. In Paris, the system will connect to the existing heating network, which already uses geothermal energy, creating a year-round thermal loop.
For Britain, this represents a quiet vindication. The Thames project was initially derided as overengineering. Now it is being studied by cities from Tokyo to Toronto. London has expanded its network to cover the Square Mile and is exploring using the River Lea and the Grand Union Canal for future phases. The key challenge is infrastructure cost: laying pipes through historic streets is disruptive. Paris has circumvented this by using the canal banks, which are already public land.
The urgency of this adaptation is underscored by the latest IPCC data. The window for preventing catastrophic heat-related mortality is closing. In Europe, heat deaths among the elderly rose 30% between 2000 and 2020. Canal cooling is not a cure all but it buys time. It reduces peak electricity demand by up to 40% and can be retrofitted to buildings without major structural changes.
Critics argue that the system is energy intensive in its own right: pumps require electricity. But as grids decarbonise, this becomes a transitional cost. The true alternative is a proliferation of air conditioning units, each using hydrofluorocarbon refrigerants that are potent greenhouse gases. Canal cooling uses no refrigerants and can be powered by renewable energy.
The biosphere collapse demands that we rethink thermal management. We cannot keep exporting heat to the atmosphere. The canals of Paris and London are, in effect, becoming heat sinks for the Anthropocene. They are a reminder that adaptation is about using what we have: water, infrastructure, and the forgotten canals that crisscross our cities. The project in Paris is expected to cut carbon emissions by 30,000 tonnes per year by 2030. That is a measurable impact. It is not enough, but it is a start.
As the planet warms, the Victorian engineers who built these canals would recognise the logic. They understood that water is a reservoir of stability. Now we are learning to use it again.
