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

Pavement

[jasonhamilton]

Makes me wonder why roofs and not pavement. There's a lot of roads and parking lots around the world. Seems like there's more surface area of those than roofs.

Re:Pavement

[drinkypoo]

The other replies have told you why you are wrong. I will tell you how to harness the principle to your benefit, but it has nothing to do with your roof. I saw it in Mother Earth News (how apparently ironic that the acronym is MEN) but the idea is old; you paint the exterior wall black, cover it with a sheet of glass or plastic, and put a vent at the top and bottom. In the summer you would prefer to cover it with white shutters to reflect unwanted solar energy. In winter, you open the shutters and the vents. Convection provides circulation.

In theory, you could do the same thing on your roof, but you'd need some sort of forced air system to bring the air down where you can use it; all you need in your home is a ceiling fan.

Re:Pavement

[KillerBob]

Ontario Highway 115, which runs between Peterborough, Ontario, and Hwy 401 just outside Toronto, is a test road. They put it in decades ago, and tested several different road surfaces, including several different types of cement and light-coloured road surfaces.

The cement has, on the whole, stood up better than the asphalt. And believe me, it gets cold in Pete.

and make all

[markringen]

and make all the birds blind. we had a man in the neighborhood who had a white roof and it was filled with dead birds. birds fly towards white objects for some reason as if it's the sky, and splatter to death.

Nice to have a Sec of Energy actually Read the Lit

[sampson7]

There are very free lunches in the world of energy production and consumption. Lightening the color of pavement and roofing materials about as close as we get. From a DOE study:

As an example, computer simulations for Los Angeles, CA show that resurfacing about two-third of the pavements and rooftops with reflective surfaces and planting three trees per house can cool down LA by an average of 2-3K. This reduction in air temperature will reduce urban smog exposure in the LA basin by roughly the same amount as removing the basin entire onroad vehicle exhaust. Heat island mitigation is an effective air pollution control strategy, more than paying for itself in cooling energy cost savings. We estimate that the cooling energy savings in U.S. from cool surfaces and shade trees, when fully implemented, is about $5 billion per year (about $100 per air-conditioned house).

Amazing, isn't it? Two to three degrees in temperature reduction in a major city just by resurfacing, repainting, and planting trees. Yeah, sure, it's not sexy. But the cost savings ... staggering. Add in the health benefits of reducing smog, plus the reduction of human misery from over-heated citys, and you wonder why we haven't done this years ago.

I know this is going to sound like a self-serving political statement from a hardcore Democrat -- but well done, President Obama. You picked a scientist to run an agency. You gave him a mission to better humanity through reducing carbon emissions and energy consumption. You gave him a platform where he would be heard. Well done indeed.

Ridiculous

[jdb2]

Paint roofs white? With the efficiency increases in photo-electric technology, why not put solar panels on every roof? Not only would we reduce the amount of heat being re-radiated back into the atmosphere but, if done on a global scale, we'd eliminate one of the primary reasons for climate change in the first place : the burning of fossil fuels. And before you respond with "but it will cost too much and generate more CO2 than it eliminates" let me give you one word : Bootstrapping. That's right -- Use the power from the existing global infrastructure for solar energy capture to build more global infrastructure for solar energy capture; That way, you would generate a minimal amount of greenhouse gases in the manufacture of new solar panels while at the same time creating a self-sustaining positive feedback loop wherein the more energy we can capture, the more energy capture infrastructure we can build, resulting in our ability to capture more energy.

I didn't RTFA but the summary sounds retarded.

jdb2

Great for Global warming....

[puppetman]

and sea levels, but not for the pH balance of the oceans, which are acidifying as they absorb additional carbon from the atmosphere.

I remember reading about green roofs (growing plants etc on the roof of buildings) and the effect it had on temperatures when done in urban environments:

Reduce heating (by adding mass and thermal resistance value) and cooling (by evaporative cooling) loads on a building â" especially if it is glassed in so as to act as a terrarium and passive solar heat reservoir â" a concentration of green roofs in an urban area can even reduce the city's average temperatures during the summer.

The Fairmont Hotel, here in Vancouver BC does this, growing herbs for the hotel kitchens.