Beating the Heat

Summer 2021 was one of the hottest summers in history. And that’s part of a longer and ongoing trend. Earth has been warming at an increasing rate for more than 100 years.

That warming affects cities in a special way. There, concrete buildings and roads absorb the sun’s heat, and tightly packed buildings block cooling breezes. Because of these and other factors, cities can be 8 to 10 degrees hotter than rural areas. This is called the heat island effect.

High heat is not just uncomfortable—it can be dangerous. It traps pollution near the ground, which can cause breathing problems, like asthma. It also puts some people at risk of heatstroke. People with fewer resources are often harmed the most, says Liv Yoon. She studies how climate change affects communities.

Many cities are coming up with ways to cope with rising temperatures. Here are some innovations that could help keep urban streets cool.

Cities are full of buildings and paved sidewalks and roads. They often lack large numbers of trees, plant life, and bodies of water that cool the air.

Chemicals released from cars and factories trap heat in cities. Large buildings use electricity, which generates heat.

The dark surfaces of many buildings absorb more heat energy than light colors. This trapped heat is slowly released after sunset.

The tall buildings and narrow streets in cities block the natural flow of cooling air.

Light-colored materials help reflect the sun’s rays better than dark surfaces. A Dutch design firm and a Swiss paint company created a reflective paint called the Coolest White. It absorbs just 12% of the sun’s rays!

Planting trees, grass, or other greenery on rooftops can cool a city’s temperature by 3 degrees Farenheit. The city of Toronto, Canada, has been requiring plants on top of new buildings since 2010.

Plants take up water from the ground and turn it into water vapor. That cools and filters the air. More trees planted along sidewalks can make surface temperatures up to 45 degrees Farenheit cooler than unshaded areas.

Adding bike lanes and walking paths reduces the heat impact of cars and trucks. Less exhaust from cars leads to cooler air.

In addition to planting trees, cities can build canopies to provide shade. The city of Austin, Texas, now requires at least half of all new parking lots to be covered from the sun.