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Comment by olivierduval | Hacker News Reader

98,1% of the heat is reflected... to where ?

It's nice to have a room "not too warm"... unless it's a lot warmer in the street and you cant go outside!

Let's imagine a "totally white" town (white on walls, streets, roofs): the air will be quite hot, or am I misunderstanding something ? So it look to me that we will trade one problem (warm outside and inside) for another one (cooler inside and warmer outside)

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What you seek to do is increase the bulk albedo of the ground/surface/neighbourhood/city resulting in the net reflected solar radiation approaching the incoming leading to minimal absorbed shortwave and thus less compensating emitted longwave (sigma * T_surf*4). If you increase albedo, you're definitely going to lower the air temperature during the day. Rays are going to bounce around and eventually leave without warming anything. Other than your body if you haven't painted yourself white.

However, with all these reflective surfaces you do get concerned with direct solar i.e. skiing in shorts & glare e.g. the "walkie-talkie" building [0].

[0] https://www.bbc.com/news/uk-england-london-23930675

“The air” is big, and warming affects winds which move the air elsewhere.

I would also mention the ground (very big, planet-sized) as a heat sink, but in cities where it’s all covered with concrete and pavement it does reflect a lot of heat back which is one reason why we observe cities hotter than the country otherwise would be

Heat mostly travels through air, air gets hot from being in contact with hot things. The heat will be reflected back to space.

What’s the problem with cooler inside and warmer outside? How much warmer outside do you suppose this white paint makes the outside?

In any case, it's better to keep the heat outside than letting it in then pump it out with an AC with some additional heat on top.

Light is reflected, not heat, and a part of it goes directly in space.

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