Painting The World's Roofs White Could Slow Climate Change

Hugh Pickens writes "Dr. Steven Chu, the Nobel prize-winning physicist appointed by President Obama as Energy Secretary, wants to paint the world white. Chu said at the opening of the St James's Palace Nobel Laureate Symposium that by lightening paved surfaces and roofs to the color of cement, it would be possible to cut carbon emissions by as much as taking all the world's cars off the roads for 11 years. Pale surfaces reflect up to 80 percent of the sunlight that falls on them, compared with about 20 percent for dark ones, which is why roofs and walls in hot countries are often whitewashed." (Continues, below.) "An increase in pale surfaces would help to contain climate change both by reflecting more solar radiation into space and by reducing the amount of energy needed to keep buildings cool by air-conditioning. Since 2005 California has required all flat roofs on commercial buildings to be white and Georgia and Florida give incentives to owners who install white or light-colored roofs. Put another way, boosting how much urban rooftops reflect would be a one-time carbon-offset equivalent to preventing 44 billion tons of CO2 from entering the atmosphere. 'For the first time, we're equating the value of reflective roof surfaces and CO2 reduction,' says Dr. Hashem Akbari. 'This does not make the problem of global warming go away. But we can buy ourselves some time.'"

Comments

Re:Pavement

[Dutchy Wutchy]

If the roads are painted white with the standard white road paint, the coefficient of friction will be reduced (much more so when wet).

Also, where is all this paint coming from? What are the environmental and economic impacts of making all of this paint?

Re:Pavement

[Avin22]

Although this would reduce the amount of energy used for cooling, heating costs would go up. For most people, it takes far more energy to heat a house than cool it. It takes 1200 KWh to cool a house in a temperate climate for a year, but it takes 12000 KWh to heat one . It is more useful to look for ways to heat a house more efficiently than cool it.

Re:Pavement

[syphax]

In the winter, a dark, hot roof doesn't heat a house very effectively (heat rising and all that- plus there's less incident solar energy).

In the summer, there's a lots of solar energy hitting your roof; and a hot roof leads to a hot attic, which retards flow of heat/hot air in the house (heat rising and all that).

So, a light-colored roof has a much more profound impact on cooling than on heating.

A metal roof will help both heating and cooling- and snow slides off them- but they are not cheap!

Re:Time out

[SnarfQuest]

Is it likely to be reversble if it isn't happening?

Re:Pavement

[CanadaIsCold]

There is a tipping point to the cement argument which is why you don't see it in truly cold locations like Canada. Cement roads have a longer lifespan than asphalt and it works out to be cheaper in some locations. In other locations ,due frost, the ground moves too much to see the return on investment. In Canada where there is heavy frost every winter a cement road would still be required to be repaired every year but at a much greater cost due to the cracks caused by frost. This is why you see more cement roads in the southern states and less in the northern. Asphalt's lower cost to install and repair makes it a better fit in colder areas. Neither is a perfect solution but each serves it's purpose in it's place. The perfect solution, as always, is to give us our flying cars.