what is the “albedo” effect which lowers the temperature?

An exceptional heat wave in a large part of France: 15 departments are on heatwave red vigilance this Monday, July 18, 2022. If everyone is looking for a little freshness, there are simple techniques. In fact, everything should be repainted in white: our houses, our cars, our roads… White everywhere, to reflect solar energy rather than store it. This is a somewhat simplistic summary of the albedo effect, the reflectivity of a surface. Take the example of fresh snow, it has a high albedo effect compared to a darker surface, such as a lake.

For climate experts, this is a factor to be taken into account in the construction sector. Le IPCC talks about it in its latest report devoted to adaptation to climate change. The experts mention in particular the technique of “cool roofs”, “cold rooftops”. It is quite simply a question of repainting the roofs in white, those of our houses, sheds, shopping centers to refresh the interior. This has been done massively in New York in recent years. In Australia, a town on the outskirts of Sidney is now even asking its inhabitants to construct buildings with a white roof.

And we can even go further by repainting cars or trains. L’idea is developed by Raphael Ménard, an architect engaged in the fight against global warming. And he did the math: if we lighten the roof of cars or trucks, we could save air conditioning, and therefore the equivalent of 500 million liters of gasoline per year, a gain of one billion euros in purchasing power and a million tonnes less CO2 in the atmosphere.

Urban planners already know the technique. In Athens, for example, in certain districts, streets have been renovated. No more dark asphalt coatings, clear coatings were preferred. Conclusion: the Ecological Transition Agency noted 4°C less in the street. Los Angeles has done the same on some roads where temperatures can reach 60°C, the streets have been repainted in white. What to fight against the formation of heat islands.