One of the worrying aspects about climate change is the melting ice in the Arctic, but not because all that melted ice would cause a rise in sea levels.

In fact, about 90% of the ice is below sea level, and as water expands when frozen, by around 9%, it is quite possible that the Arctic melting would have zero impact on sea levels.

However, ice is also very reflective and a lot of solar energy hitting the earth is reflected back into space by the Arctic ice. No ice, and all that heat gets absorbed by the sea, warming it – and in turn causing sea volumes to expand and sea levels to rise.

So, how about increasing the amount of the earth’s surface that reflects the solar radiation? It’s something I have occasionally pondered about, but lacked the resources/skills to work out the maths.

Some boffins have also thought about similar ideas – such as seeding clouds over oceans or even more brazenly, putting mirrors in space.

Now another report appears on my mailing list – where some boffins have actually looked at what would happen if you liberally splashed white paint on the roofs of city buildings.

Asphalt roads, tar roofs, and other artificial surfaces absorb heat from the Sun, creating an urban heat island effect that can raise temperatures on average by 2-5 degrees Fahrenheit (about 1-3 degrees Celsius) or more compared to rural areas. White roofs would reflect some of that heat back into space and cool temperatures, much as wearing a white shirt on a sunny day can be cooler than wearing a dark shirt.

Their simulations, based on an idealized view of different types of cities around the world, indicate that, if every roof were entirely painted white, the urban heat island effect could be reduced by 33 percent.

I was reminded of the issue today though, as someone has had an accident outside the flat and most of the road is now covered in whitewash. I wonder what the impact would be if every road was also covered in whitewash – presuming one can be developed that lasts more than a few days.

I am as it happens, quite a fan of green roofs, where the tops of buildings are given over to garden spaces for the residents or shrub-land for the local wildlife and it is a pity that so few new buildings in London are thus designed.

Obviously, the Gherkin might have a bit of a problem!

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4 Comments

  1. Apparently it’s been proposed for Melbourne City rooftops in the near future in a bid to reduce reliance upon air-con, reduce carbon emissions, etc.

  2. heat reflective roof paint

    Very interesting article. Is there data on how white roofs compare to, say, rooftop gardens, which can both absorb heat and offset carbon dioxide emissions?

  3. The difference between white roofs and roof top gardens, if nothing else, would be the weight and expense. Significant factors! Enough to make it offset any advantages whatever they might be.

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