TREES ARE A QUIETER WAY TO COOL OUR CITIES / THE FINANCIAL TIMES OP EDITORIAL

Trees are a quieter way to cool our cities

Urban forestry used with precision can reduce the temperature several degrees without straining the power grid

Carlo Ratti

Amsterdam’s Lomanstraat features criss-cross trees along its entire length. Trees such as these provide shade, but also lower air temperatures through evapotranspiration © Getty Images

“Shall I compare thee to a summer’s day?” 

No, Shakespeare, please don’t. 

What once evoked bucolic warmth now suggests suffocation. 

The trite seasonal headline is back: Europe is again gasping under record heat, with several countries experiencing their hottest periods on record. 

So how do we cool our cities? 

For many, the reflex is air conditioning (AC). 

But before rushing to install more cooling units, we may want to consider a humbler, quieter solution: trees.

As the climate changes rapidly, some argue that AC should no longer be seen as a luxury, but a lifeline. 

Once indoor temperatures exceed 23C, sleep, health and productivity all falter. 

The disparity in access to it is deadly. 

Between 2000 and 2019, Europe experienced an average of 83,000 heat-related deaths a year — more than four times the number in North America where AC is more common. 

Clearly, it can save lives. 

But it is a lifeline with a frayed rope.

First, it strains the power infrastructure. 

In the last two weeks of June 2025, demand for cooling caused electricity use in the EU to jump 7.5 per cent year-on-year. 

The consequences were visible. 

On July 1, the Italian cities of Florence and Bergamo experienced widespread blackouts during a severe heatwave. 

People were trapped in lifts and shops shut as payment systems failed. 

We are cooling ourselves into gridlock.

AC also bakes our streets — venting waste heat outside intensifies the heat island effect. 

The cooler we keep our interiors, the hotter we make our public spaces. 

The effects on the urban climate are especially harsh for those without access to cooling, widening inequality.

Nature can offer a better way. 

We have long known that trees have an important effect on the urban environment. 

They provide shade, but also lower air temperatures through evapotranspiration. 

Yet comprehensive data on greenery’s cooling potential has been scarce. 

Thermal studies have been limited, partly due to the difficulty of analysing large volumes of data.

Artificial intelligence is changing this. 

Our MIT team, together with the Dubai Future Foundation, has used AI and thermal imaging to measure how vegetation affects urban microclimates. 

In 2025, we collected data in Los Angeles, Dubai, Amsterdam and Boston, scanning streets and public spaces to assess how greenery performs.

We showed that trees maintain a cooler temperature than the surrounding urban surfaces as much as 15 degrees in the hottest times of the day. 

But not all plants are created equal. 

Shrubs and grass provide minimal cooling. 

Trees with dense canopies perform far better in many locations. 

In Dubai, native drought-resistant neems outperformed imports. 

Los Angeles’s iconic palms — tall and sparse — offered little relief. 

Movie stars of the boulevard, yes; climate heroes, not so much. 

Placement is critical, too. 

Trees planted alongside buildings deliver more comfort than those in wide-open parks. 

In Amsterdam, mature deciduous trees flanking narrow streets cooled their surroundings by up to 5°C. 

Taken together, our findings begin to form a “cooling catalogue” — a data-driven guide for planting the right trees, in the right places, for maximum climate impact.

Yes, trees have their own demands: water, competition with underground infrastructure, patience. 

In historic cities, canopies require lengthy consultations — in Paris, plans to expand greenery next to Notre-Dame met a tangle of nostalgia and horticultural arguments.

Yet, in a hotter world, trees should be considered more than decoration. 

This ancient infrastructure can cool not just our buildings but the cities themselves. 

And with AI, we can now plant better, with precision urban forestry. 

In a warming world, the smartest climate tech may be rooted in the ground — and it doesn’t strain the power grid.

The writer is a professor at MIT and Politecnico di Milano, and director of Venice’s 2025 Biennale Architettura