The White Revolution
When I was recently transcribing the interview that Vinod Khosla did for the Milken Institute, something he said caught my attention:
Hybrids are an uneconomic way to reduce carbon dioxide. If you go to hybrids or electric cars, your cost of carbon reduction is about $100/ton. If you have 10 ways of reducing carbon at $50/ton, why would you spend $100? My beef is not with hybrids; we are investing in hybrid batteries; there is a good market and we can make money at it. But do I believe it’s going to solve the climate change problem? No. Save yourself the five grand, and instead paint your roof white. You will save more carbon that way.
He then cited this paper by Art Rosenfeld at Lawrence Berkeley Lab: “White Roofs Cool the World, Directly Offset CO2 and Delay Global Warming“.
Yesterday, speaking in London, Energy Secretary Steven Chu picked up on that theme:
Speaking in London prior to a meeting of some of the world’s best minds on how to combat climate change, Dr Chu said the simple act of 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.
The principle could also be extended to cars where white or “cool colours” designed to reflect light and radiation could make vehicles more energy efficient in summer. “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.
Asked about whether the US administration has any plans to manipulate the climate artificially using large-scale geoengineering programmes, Dr Chu said there were no such plans “at this time”. But painting surfaces white is one geoengineering proposal that he is taking seriously.
I have to admit that I haven’t read the paper, so I can’t comment whether there may be major flaws in the idea. It is certainly interesting, though I do wonder about the scale of painting everything white. But it would be a lot easier to paint roofs white than to go down some of the other pathways that have been floated for slowing carbon emissions. The only down side I can see is that I will have to spend more money on sunglasses. Just thinking about white roads makes my eyes hurt.