Cities Are Heating Up. Better Infrastructure Can Cool Them Down.

In a city, a grassy park might be a place to stretch out with a book, an asphalt road your route to work, a building wall a canvas for a mural. But beyond their familiar roles, each of these surfaces plays a critical and often unseen role in shaping urban heat.

Many cities are warming at twice the global rate — a problem that's only worsening with rapid urbanization. And while rising temperatures are a problem everywhere, some cities and neighborhoods (often the poorest and most vulnerable) swelter more than others.

The reason for this comes down to the urban environment. Built infrastructure like roads, buildings and sidewalks, as well as natural infrastructure like trees and water bodies, determines how heat moves through a city. In most cities, the abundance of dark, impervious surfaces, like asphalt, traps heat and drives temperatures up — contributing to the urban heat island effect.

But urban infrastructure can also be one of the most powerful tools to keep people cool, without relying on energy-hungry air conditioning. The key is focusing on "surface infrastructure" — the places where the physical city and the atmosphere interact. In fact, cities around the world are showing that seemingly simple changes to surfaces, like painting roofs white or planting trees, can have a surprisingly big impact on temperatures. It's a matter of knowing how and where to use these solutions.