A white roof that will reflect nasty Infrared back into space

Scientist, Hashem Akbari, wants you to paint your house roof white in a attempt to slow down global warming.

Its’a simple enough idea, backed by good science, we could all do it this weekend and we would slow down the onset of dangerous global warming levels quite significantly. Akbari has launched a worldwide campaign to encourage the world’s largest cities to come together and literally paint the towns white. California is already on the case and commercial properties there have been painting their roofs white since 2005, so should the rest of us do the same?

The science is logical: Black and darker colours absorb light and the heat (infrared), from the sun, whilst white or lighter colours reflect it. Absorbed heat will build up and contribute to climate change whereas reflected heat has the chance to escape into space.

It is this principle that is leading to the acceleration of ice melting at the poles. White ice reflects heat back into space but the dark surface of the sea absorbs the heat and contributes to global warming. As the earth warms up, more ice melts which exposes the darker sea underneath. Obviously the warmer it gets, the more ice melts and the more sea is exposed making the situation worse.

Any man made surface we can paint white will increase the amount of heat reflected back into space. Akbari suggests that 1,000 square feet of dark roof painted white will offset 10 tonnes of carbon dioxide every year. Daisy Cottages is based in Gateshead so we rang our local council to ask if we could do it. After two minutes chatting with the planning department, we were told that as long as our building wasn’t listed or in a conservation area we could paint our roof white.

For this kind of thing to have a significant effect it needs to be done on a wide scale, making it a geo-engineering project. Geo-engineering basically means the whole planet needs to get behind it.

The idea is not limited to roofs, any man made surface such as roads could be part of this plan.Roads make up a significant portion of urban surfaces and the more we can paint, the more heat energy will be reflected. Painting roads white presents a safety problem though because shiny white roads would dazzle drivers. The solution is simple because we only have to reflect the heat (the infrared), and not all of the sunlight. Akbari says this shouldn’t be a problem because light grey colours are still much better than black for reflecting heat. There are also some experimental paints and pigments which reflect over 80 per cent of the Infrared whilst only reflecting 20 per cent of the white light.

There are other benefits too. According to a report by David Adam in The Guardian, painting roofs white could reduce temperatures by 2-3 degrees, reducing smog and the energy needed to run air conditioning. In cities such as Los Angeles this could represent a significant energy change. Given all these benefits, shouldn’t we all be (safely) on our roofs this weekend, painting those dark slates white? If the science is good, and the benefits are as significant as the estimates suggest, shouldn’t governments everywhere legislate for this?

Akbari’s full report presentation can be found here.