Painting The World's Roofs White Could Slow Climate Change 712
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.'"
Re:Pavement (Score:5, Informative)
From TFS:
that by lightening paved surfaces and roofs to the color of cement
Personally, I wouldn't want to drive on a surface that bright; I'd be squinting even with my sunglasses on!
Also, as a current resident of California, I can see the value in having a light-colored car or house, but as a former resident of New Hampshire, I can tell you that having a black car and black roof on a cold but sunny winter's day is very helpful! Snow slides off my car roof with ease, and it means I didn't have to turn the heat up quite so much!
White roofs (Score:3, Informative)
and, the original source: Powerpoint presentation from LBL: "Global Cooling: Increasing World-wideUrban Albedos to Offset CO2," Hashem Akbari PDF file [mit.edu]
Double benefit (Score:3, Informative)
Anyone know what the environment/economic cost of making all that whitewash is?
Re:and make all (Score:3, Informative)
Re:Pavement (Score:4, Informative)
not only that, the pain they use on roads is terrible for traction. Even just stop lines can be brutal for motorcycles.
You would have to add the pigment to the actual road material for it to be at all practical.
Re:White asphalt? (Score:2, Informative)
Concrete is lightly colored, abit off white.
Also, concrete paving lasts longer and needs less maintenance. The reason asphalt is used so much is its cheaper in the short term.
Tire wear on the concrete will turn it blackish, so I guess now all we need is white rubber?
Re:Unfortunately... (Score:3, Informative)
You need about 100 g of paint to cover a square meter. Suppose that the paint costs 1 kg worth of fuel to manufacture. The amount of sunlight it reflects over 10 years in a sunny climate is on the order of 50 gigajoules, or about 1000 kg of fuel to burn. Even if only 10% of the heat has to be cooled away by airconditioning, it is a good deal: invest 1 kg of fuel; save 100 kg in fuel for the airconditioning. (I assume that the inefficiency of a power plant compensates the efficiency of a heat pump)
I'm not sure how making the pavement lighter will reduce CO2 emissions. It would reduce the greenhouse effect a bit due to less infared radiation being trapped - increasing the world's albedo by 1% or so would have a quite significant impact on the climate, but it is difficult to translate than into an absolute amount of CO2 emission.
Re:Pavement (Score:5, Informative)
http://www.eoearth.org/article/Cool_paving [eoearth.org]
However, one of the current hangups is how to keep them light? Unless we can also change the rubber in the tires to be lighter color as well, the road surfaces just end up black again in high traffic areas like California.
Re:why roofs in hot countries are whitewashed (Score:5, Informative)
That's nice for the hot countries. What about cold countries? Maybe we like having black roofs and roads to melt the snow faster if there's a little opening?
Yes. Or nearly so. I just happened to be doing some research on roof treatments. There are basically two types -- for flat roofs. Angled roofs are a different story since they're angled for snow and rain shedding. The two types of flat-roof coatings are white paint and aluminum paint.
Here's the link: http://eetd.lbl.gov/coolroof/coating.htm [lbl.gov]
White paint coatings use titanium dioxide as a pigment (very, very white) and reflect 70-80 percent of incident light. That means they keep the roof cool in the summer. They are, however, reasonably transparent to IR from below, so unfortunately do nothing to hold heat in during the winter.
Aluminum paint coatings use little flakes of alumnimum and reflect about 50-60 percent of incident light. That means they also keep the roof cool in the summer. They are, however, much less transparent to IR from below, so help keep in heat during the winter by reflecting it back down.
Then again, nothing stops you from painting your flat roof white or aluminum and unrolling black sheeting during the winter to help absorb heat from the sun.
Re:White asphalt? (Score:2, Informative)
http://www.whitetopping.com/faq.asp [whitetopping.com]
Alternatively, you can put additives such as limestone into the asphalt mix to help lighten the color.
Re:Pavement (Score:4, Informative)
Same here in Arizona; freeways are built from concrete, and then a layer of rubberized asphalt is paved over it. Until a few years ago, most of the freeways were bare concrete; IIRC one of the major reasons for the asphalt was to reduce traffic noise.
Re:Pavement (Score:5, Informative)
In Florida, we have only one season:
#RandomWeatherPattern
Huh? what are you talking about? (Score:4, Informative)
Re:Pavement (Score:3, Informative)
Re:and make all (Score:5, Informative)
Re:Time out (Score:3, Informative)
Re:Time out (Score:3, Informative)
Great Cthulhu's corpse, do we have to go through this again?
Let's go over the chart [wikimedia.org]. 1998 (the big uppy spiky thing near the end of the graph) was a huge warm year, because of El Nino, not because of global warming per se. 2008 (the downy liney thing at the end of the graph) was an exceptionally cool year, because of La Nina, and not because of any long-term cooling trend.
Get rid of those two points, and the whole "we're going through a global cooling period" argument melts away like so much glacier.
Excluding 1998, every year of the new millennium has been warmer than every single year that has come before it, back thousands of years.
From Wikipedia [wikipedia.org]:
Don't paint your house, plant a tree (Score:3, Informative)
Dyson published a paper titled "Can We Control the Carbon Dioxide in the Atmosphere?" His answer was yes, and he added that any emergency could be temporarily thwarted with a "carbon bank" of "fast-growing trees." He calculated how many trees it would take to remove all carbon from the atmosphere. The number, he says, was a trillion, which was "in principle quite feasible."
You can disagree [scienceblogs.com] with his math, but he does raise an interesting point. Sometimes the best ideas are also the simplest.
As an aside, I noticed that a lot of his critics seem to focus on what happens if you extract too much carbon from the atmosphere - which begs the question of how can Global Warming be an irreversible, extinction-threatening process if it's so 'easy' to fight.
Re:Pavement (Score:5, Informative)
It's a little of this, or a little of that.
I've noticed, new asphalt in the Florida summer (say 90F to 110F) roads turn into mirages, Entire cars can disappear in the at less than 1/10 mile. You can see the heat rising from them.
In older asphalt roads, where they're sun bleached and worn, the heat isn't as much of a problem.
And I've never seen it on concrete roads.
I've wondered about roads and roofs being a contributing factor to global warming. There's a lot of square miles of roofs and roads that have increased relation to the population. It's always been notable that cities are hotter than the countryside surrounding them.
I've wondered about the heat put off by internal combustion engines. We're taking massive amounts of stored energy (oils, etc) and turning them into heat and motion. How many BTU per hour does an average car put off? In passenger vehicles, even in the winter, a small fraction of that heat is redirected into the passenger compartment, and can turn it into a freakin' oven. Look at the size of the heater core versus the radiator.
In the summer, that's increased, as the load on the cooling system is added onto by running the A/C in the car (more load on the engine). The amount of heat moved from the passenger compartment to the outside should be a wash, as should the heat transfer from a building.
Re:Pavement (Score:5, Informative)
During the winter when it reached -8 degrees outside, my flat without any heating was at 16 degrees. My neighbours have the same issue, we only have the one small flat below us so the heat isn't coming from downstairs.
I can think of several other new buildings which suffer from this problem. If your going to argue about the color of a building mandating improved heat conservation should remove most of the heating costs.
Re:Pavement (Score:4, Informative)
In physics, a black body is a perfect absorber of light, but by a rule derived by Einstein it is also, when heated, the best emitter. [wikipedia.org]
so if your house/car/etc is heated, then yes it emits more heat from the body if black. Thus it is a worse insulator and (as you observed) heats the snow on the outside of your car faster. So yes if your goal is to heat the outside of your car in winter, black is best. If keeping the stuff on the inside warmer than the outside, is your goal, it may not be best in black (definitely not assuming a lack of radiated light, like at night.)
Re:Huh? what are you talking about? (Score:3, Informative)
Re:Pavement (Score:5, Informative)
Not just quick dry... All cement is an exothermic reaction. And would people SERIOUSLY stop calling concrete cement. Roads are made of concrete, which is a mixture of cement, aggregate, and water. Cement is only the binder of the mix.
Re:Pavement (Score:3, Informative)
Re:Pavement (Score:1, Informative)
Actually the trick with asphalt is to take the black stuff out.
What is left behaves very similarly to paving grade asphalt, but it is a yellowish, translucent, highly viscous liquid at room temp. The process is enormously expensive though and could not produce a cost effective road.
TiO2 can be used to make asphalt white but by the time you get enough in there is stops acting like asphalt.
Re:Pavement (Score:3, Informative)
What do you mean they're not cheap? The corrugated steel roof has been the roof of choice for people who can't afford tarpaper for ages.
They're also one of the most common kinds of roof in Australian houses. Though it does tend to look a bit better [colorbond.com] than the kind you are referring to.
Re:Pavement (Score:4, Informative)
If all you are doing is laying down asphalt maybe it will go that quickly. After you have a few layers on a main road it takes longer because
1) you can't shut the road down completely
2) you can only work at night
3) you have to mill off the old layers first
4) you have to clean off the pavement right before laying asphalt
5) you have to put some sort of black goo down so the new asphalt sticks to the old
6) Whoever is doing the contracting seems to wait for random amounts of time between stages.
7) you do it in 5 mile chunks.
Near where I live there is a major interstate and it can take a month to re-pave, driving over the grooved pavement makes a lot of noise and the transitions from the grooved to old asphalt mean your car goes up a couple of inches.
I suspect 6 and 7 have more to do with bureaucracy/lowest bidder/political considerations than to technical reasons.
Re:Pavement (Score:2, Informative)
I don't believe most roads change color because of tire rubber- excepting a few high traffic areas. Most change color to match the aggregate (read: rock) that's in in the asphalt- usually some sort of plain greyish rock.
When I drove through AK/CD the roads are green or red or other colors that match the color of the local rock they used.
Perhaps all they need to do is use a bright white rock in the aggregate?
Mr Chu is a moron (Score:1, Informative)
Half of the energy from the sun is IR that we can't see anyway. There has been roofing materials on the market for several years which still look dark to us but don't absorb much energy because they reflect the IR radiation we can't see anyway.
Doing stupid things like expecting everyone to rush out and paint their roofs white is both moronic and unecessary.
Re:and make all (Score:2, Informative)
Re:Pavement (Score:3, Informative)
To put that into perspective: total length german Autobahn [wikipedia.org]: 12 200 km, US Interstate Highway System" [wikipedia.org] 75 440 km, that's about 6 times longer. Population 80 vs 300 (3.75 times) million, area 360 000 vs 9 900 000 km^2 (27.5 times)...
Autobahn is cement? I don't think so (Score:4, Informative)
Also, mean temperatures in Germany (13C) are much higher than in Canada (-8C).
If you want proof, take a look [almostsmart.com]:
1) It's asphalt.
2) The beer is not frozen.
Re:Autobahn is cement? I don't think so (Score:4, Informative)
Europe is more densely populated, and concrete roads just don't stand up to the traffic levels. The old Newark bypass on the A1 and the originally-concrete M11 in the UK are testament to that.