Can we cool the planet by painting rooftops white?
"We know that dark colours absorb heat, and that light colours reflect heat away," says climate researcher.
Published
Have you ever sat on a black bench in the blazing sun?
Then you know it can get hot – dark colours absorb heat.
White, on the other hand, reflects it away.
This has led climate researchers to explore new ideas.
Geoengineering
"The very best thing would be if we stopped polluting," says Helene Muri.
She has been studying climate for over 20 years and works at the research institutes NILU and NTNU.
"But cutting emissions has proven to be difficult for us," she says.
So researchers are looking for other ways to cool the planet.
They call it geoengineering.
"Geoengineering means using technology to slow down global warming," says Muri.
Blocking sunlight
Researchers are exploring several ideas. Some involve:
- Removing CO2 from the atmosphere.
- Reducing the amount of sunlight that heats the planet.
"There are different ways to do that," says Muri.
One approach is to release dust or gases high into the atmosphere.
This would act like a giant parasol, blocking sunlight and cooling the Earth.
You can read more about it here.
But researchers are also looking at other methods...
White rooftops in New York
"There's been talk of painting rooftops white. Could that help cool down the planet?"
"We know that dark colours absorb heat, and that light colours reflect heat away," says Muri.
When the sun shines on a light-coloured roof, some of the heat is reflected back into space.
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"That's why they've started painting rooftops white in New York," she says.
The project was launched to help the city adapt to climate change.
Muri says that white paint can make it cooler in the areas where it is applied.
One study showed that white roofs in New York were six degrees cooler.
"But it probably won't have much effect on the global temperature," she says.
So white paint can't save the planet – but it can be a helpful addition.
"We have to cut our emissions," says Muri.
Nature's cooling power
The idea that light-coloured surfaces can cool things down comes straight from nature.
"Some places on Earth are naturally light," says Muri.
Think of all the snow and ice in the Arctic, and the sand in the Sahara Desert.
"These light surfaces help reflect sunlight back into space," says Muri.
They play a key role in regulating the planet’s temperature.
But as snow and ice melt, the ground darkens.
"That means it will start absorbing more heat," says Muri.
The whitest paint ever made
Research plays an important role in the search for cooling solutions.
In 2021, researchers from the USA made it into the Guinness World Records.
They had developed the world's whitest – and most cooling – paint.
It reflects nearly all sunlight, making roofs and walls cooler than the surrounding air.
This could help our climate.
"Light-coloured paint can reduce the need for air conditioning, which helps save energy," says Muri.
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Translated by Alette Bjordal Gjellesvik
Read the Norwegian version of this article on ung.forskning.no
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