For centuries, humanity has explored and harnessed the cooling and heating capabilities of cities.
As extreme heat breaks records worldwide, a lesser-known fact is offering hope for humanity: even during the most extreme heatwaves, certain areas of cities remain cool, unaffected by the heat. This indicates that the cooling potential of cities is not out of reach if we know how to leverage the simple measures used by ancient civilizations.
Planting trees significantly improves living environments.
Lessons from Ancient Civilizations
In Ancient Rome, architects encouraged the construction of narrower streets to reduce temperatures in the late afternoon. This design limited direct sunlight exposure, thereby cooling the air. Similarly, the Greek islands utilized whitewashed architecture with bright walls and roofs to reflect sunlight and cool surrounding areas.
Thomas Jefferson, one of America’s founding fathers, also proposed an innovative solution for cooling cities in the hot, humid regions of the Southern United States. He suggested building in a grid pattern, alternating between dense construction blocks and areas with lush vegetation. This approach not only provided shade but also promoted airflow, helping to cool the air.
Whitewashed architecture with bright walls and roofs reflects sunlight.
The Urban Heat Island Effect: How Cities Heat Themselves
In the book “Radical Adaptation: Transforming Cities for a Climate-Changed World”, researchers explored how modern cities inadvertently increase their own temperatures, leading to the urban heat island effect. Four main factors contribute to cities becoming hotter:
- Loss of Vegetation: When developers cut down trees to make way for buildings and infrastructure, the shade from tree canopies is lost, and evapotranspiration from leaves decreases, reducing natural cooling effectiveness.
- Heat-Absorbing Building Materials: Asphalt, concrete, and dark roofing materials absorb heat from the sun and radiate it into the surrounding environment, raising the overall temperature of the area.
- Heat Waste: Heat generated from industrial processes, vehicle exhaust, and air conditioning systems exacerbates the situation.
- Heat Canyon Effect: In areas with high-rise buildings, heat radiated from concrete and asphalt surfaces gets trapped, increasing temperatures.
These factors can raise temperatures in cities by 10 to 20 degrees Fahrenheit (5.6 to 11 degrees Celsius) during hot summer afternoons, posing serious health risks, particularly for those without air conditioning.
Ancient Roman architects encouraged building narrower streets to reduce temperatures in the late afternoon.
Simple Steps to Cool Cities
In fact, understanding how cities heat themselves is the first step in finding ways to cool them down. It’s crucial for cities to significantly reduce greenhouse gas emissions to combat global climate change. According to Inverse, urban areas are responsible for over 70% of greenhouse gas emissions from energy use, and the population in these cities is rapidly growing. Therefore, measures to adapt to high temperatures are necessary even as efforts to reduce greenhouse gas emissions are underway.
Research has shown that simple measures can significantly reduce the urban heat island effect and provide substantial health benefits. At the Georgia Tech Urban Climate Lab, scientists have collaborated with cities to assess cooling potential through urban heat management strategies. Actions such as increasing tree cover and using cool materials for roads and roofs have proven effective in lowering temperatures.
For example, planting trees in just half of the available space can reduce afternoon summer temperatures by 5 to 10 degrees Fahrenheit (2.8 to 5.6 degrees Celsius) and decrease heat-related mortality rates by 40 to 50%. New York City has successfully aimed to plant 1 million trees, significantly improving the living environment.
The urban heat island effect contributes to making cities hotter.
Urban Cooling Strategies
Light-colored building materials can also significantly help reduce temperatures. Just as you feel cooler wearing a white shirt instead of a black one under the sun, light-colored surfaces reflect sunlight better and absorb less heat. Los Angeles has been a leader by requiring cool roofs for all new homes since 2013.
In addition to planting trees and using cool building materials, cities can redesign public spaces for cooling. Some street parking lanes can be replaced with areas featuring green vegetation, which helps absorb rainwater and cool the surrounding air. Cities like Atlanta, Dallas, Louisville, and San Francisco have demonstrated that combining these strategies can reduce neighborhood temperatures by over 10 degrees Fahrenheit (5.6 degrees Celsius) on hot days while decreasing heat-related premature mortality rates by 20 to 60%.
Light-colored building materials can also significantly help reduce temperatures.
Urban cooling strategies not only help lower temperatures but also enhance community resilience to climate change. A cooler city is a safer and more vibrant city. By learning from ancient civilizations and applying simple yet effective measures, we can transform modern cities into better living spaces, even in the face of the challenges posed by global climate change.
