Paint it white

Global warming may seem like an overwhelmingly complex problem to tackle. But one scientist thinks the answer is brilliantly simple: a lot of white paint.
--------------------------------------------------------------------------------Akbari is a scientist who has come up with a new way to fight global warming. It could be the easiest solution you've never heard of.
His big idea is based on principles as old as the whitewashed villages that scatter the hills of southern Europe and North Africa. Turn enough of the world's black urban landscape white, he says, and it would reflect enough sunlight to delay global warming, and grant us some precious breathing space in the global struggle to control carbon emissions.

Akbari is poised to launch a campaign to paint the world white. He wants dozens of the world's largest cities to unite in an effort to replace the dark-coloured materials used to cover roads and roofs with something a little more reflective.

It sounds simple, but the effect could be dramatic. Study after study has shown that buildings with white roofs stay cooler during the summer. The change reduces the way heat accumulates in built-up areas -- known as the urban heat island effect -- and allows people who live and work inside to switch off power-hungry air-conditioning units.

Together, roads and roofs are reckoned to cover more than half the available surfaces in urban areas, which have spread over some 2.4% of the earth's land area. A mass movement to change their colour, Akbari calculates, would increase the amount of sunlight bounced off our planet by 0.03%. And, he says, that would cool the earth enough to cancel out the warming caused by 44 billion tonnes of carbon dioxide (CO2) pollution.

If you think that sounds like a lot, then you're right. It would wipe out the expected rise in global emissions over the next decade. It won't solve the problem of climate change, Akbari says, but could be a simple and effective weapon to delay its impact -- just so long as people start doing it in earnest. "Roofs are going to have to be changed one by one, and to make that effort at a very local level, we need to have an organisation in place to make it happen," he says. Groups in several cities in the United States, including Houston, Chicago and Salt Lake City, are on board with his plan, and he is talking to others.

Akbari says his plan is more workable than other geo-engineering ideas. The science is simple. Sunlight reflected from a surface does not contribute to the greenhouse effect, which drives global warming. That problem comes when dark surfaces soak up sunlight and send it back up as thermal energy, at just the right wavelength to rebound off CO2 in the sky.