Nobel scientist's white hot idea to reduce global warming

The answer to global warming, says US President Barack Obama's top adviser, is ... paint your house and car roof white.

Steven Chu, the US Secretary of Energy and a Nobel prize-winning scientist, told Britain's the Independent that making roofs and pavements white or light-coloured would help to reduce global warming by both conserving energy and reflecting sunlight back into space.

It would, he said, be the equivalent of taking all the cars in the world off the road for 11 years.

Dr Chu said painting roofs white could have a dramatic impact on the amount of energy used to keep buildings comfortable, as well as directly offsetting global warming by increasing the reflectivity of the Earth.

"If that building is air-conditioned, it's going to be a lot cooler, it can use 10 or 15 per cent less electricity," he said.

"You also do something in that you change the albedo of the Earth - you make it more reflective. So the sunlight comes down and it actually goes back up - there is no greenhouse effect," Dr Chu said.

When sunlight is reflected off a white or light-coloured surface, much of that light will pass through the atmosphere and back into space, unlike the infrared radiation emitted from the Earth's warmed-up surface, which is blocked by greenhouse gases and causes global warming.

"What we're doing is that, as we put in more greenhouse gases, we're putting in more insulation for infrared light. So if you make white roofs and the sunlight comes in, it goes right through that [insulation]," said Dr Chu.

"If all vehicles were light-coloured, there could be considerable savings because then you can downsize the air-conditioning ... and downsizing the air-conditioner means more efficient air-conditioning and a considerable reduction in energy," he said.

"If you look at all the buildings and make all the roofs white, and if you make the pavement a more concrete-type of colour than a black-type of colour, and you do this uniformly ... it's the equivalent of reducing the carbon emissions due to all the cars in the world by 11 years," he said.

"It's like you've just taken them off the road for 11 years.

"It's actually geoengineering."