Resurfacing urban areas to offset 150 billion tons of carbon dioxide

Apr 12, 2012
Sun rays appear through the clouds. Scientists sketched a vision on Friday of converting the world's cities into giant sunlight reflectors to help fight global warming but met with scepticism from fellow academics.

Imagine a world where the rooftops and pavements of every urban area are resurfaced to increase the reflection of the Sun's light rays. Well, this is exactly what a group of Canadian researchers have done in an attempt to measure the potential effects against global warming.

In a study published today, 13 April, in IOP Publishing's journal Environmental Research Letters, researchers from Concordia University created this scenario to see what effect a global increase in surface reflectance would have on and our own (CO2) .

They estimate that increasing the reflectance – commonly known as albedo – of every urban area by 0.1 will give a CO2 offset between 130 and 150 billion tonnes. This is equivalent to taking every car in the world off the road for 50 years, assuming a single car gives off around 4 tonnes of carbon dioxide a year.

This could also provide huge financial gains: CO2 is currently traded at $25 a tonne meaning savings could be in the range of $3300 and $3800 billion dollars. Albedo is measured on a scale ranging from 0 for a non-reflecting, perfectly black surface to 1 for a perfectly white surface. The albedo of all roofs can be increased, on average, by 0.25 and all paved surfaces can be increased by about 0.15. The researchers believe this will increase a city's overall albedo by about 0.10.

Researchers have long proposed that changing the albedo of a surface could be an effective way of reducing CO2 emissions. A change could effectively cool buildings that would usually retain heat and therefore reduce the use of air-conditioning systems; it could also improve outdoor air quality and offset the warming that the world is currently experiencing.

In this new study, the researchers showed that increasing the albedo of a 1m2 surface by 0.01 would have the same effect on global temperature, over the next 80 years, as decreasing emissions by around 7kg of CO2.

The researchers used a dataset of all global urban areas, called the Global Rural and Urban Mapping Project (GRUMP), to give a realistic estimate of the effects of a global albedo change. In addition to the very large carbon dioxide offset, the researchers calculated a potential decrease in temperature of about 0.07°C

Completely changing the surfaces of all the world's roofs and pavements seems like a mammoth task; however, the researchers believe that it is possible if promoted in the right ways.

"Typically roofs are resurfaced (or changed) about every 20-30 years; paved surfaces are resurfaced about every ten years. When roofs or paved surfaces are installed, they can be changed to materials with high solar reflectance, typically at no incremental cost," the researchers write.

Lead author Professor Hashem Akbari said: "It is all based on planning, codes and policies. If we really put the nuts and bolts in place, we can get close to 100 per cent of urban areas increasing the albedo of surfaces."

Fast facts:

-- Over 50% of the world's population currently lives in urban areas. This is expected to increase to 70% by 2040.
-- and roofs comprise over 60% of urban surfaces (25% roof and 35% pavement).
-- According to the GRUMP model, the combined size of global is around 2 million km2.

Explore further: Tourists evacuated amid Iceland volcano concerns

More information: The long-term effect of increasing the albedo of urban areas, Hashem Akbari et al. 2012 Environ. Res. Lett. 7 024004. iopscience.iop.org/1748-9326/7/2/024004/article

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User comments : 23

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Deathclock
2 / 5 (11) Apr 12, 2012
How much CO2 would be released in the production, transportation, and installation of all of this new roofing material?
Telekinetic
2.7 / 5 (6) Apr 12, 2012
Chicago has already instituted a program to create green roofs on its city buildings since 2008. Vegetable gardens can be grown, people can be fed, and solar heat will be mitigated. It requires some engineering surveys in weight load capacity and water usage, but it is also a great educational tool for kids to get involved. They would be latter day urban "Victory Gardens" like this country had during WWII.
Deathclock
1.9 / 5 (8) Apr 12, 2012
Chicago has already instituted a program to create green roofs on its city buildings since 2008. Vegetable gardens can be grown, people can be fed, and solar heat will be mitigated. It requires some engineering surveys in weight load capacity and water usage, but it is also a great educational tool for kids to get involved. They would be latter day urban "Victory Gardens" like this country had during WWII.


This is not what the article is talking about, "green" roofs with gardens do not increase albedo
rKoso
4 / 5 (5) Apr 12, 2012
Deathclock, likely the same amount of CO2 as is currently released by the production, transportation, and installation of replacement roofing material. As they mention, most roofs are replaced every 20-30 years, so 3-5% are replaced every year.

What I'm confused/concerned about is that this seems like simply trying to force energy back at the sun to manipulate temperatures. CO2 emissions don't actually change. This quickly becomes a delicate balancing act. Global cooling doesn't sound much more pleasant than warming. And if we 'correct' with albedo changes, when emission controls continue to get implemented, do we intentionally pollute more? Or resurface again to try and reverse the effect?
bewertow
2.3 / 5 (6) Apr 12, 2012
Probably would be better to plant rooftop gardens.
Telekinetic
1.9 / 5 (8) Apr 12, 2012
Chicago has already instituted a program to create green roofs on its city buildings since 2008. Vegetable gardens can be grown, people can be fed, and solar heat will be mitigated. It requires some engineering surveys in weight load capacity and water usage, but it is also a great educational tool for kids to get involved. They would be latter day urban "Victory Gardens" like this country had during WWII.


This is not what the article is talking about, "green" roofs with gardens do not increase albedo

Rooftop gardens absolutely increase albedo, because plants and trees increase albedo. "Google" it while you kick yourself in the ass, dunce.
Peter_Y
1 / 5 (3) Apr 12, 2012
There are many areas of the world where people want to *retain heat in their buildings, not cool them! .. and other areas that want the heat in their winters, but want cooling in their hot summers.
Also, road markings use white paint. They would have to change to black road markings if the pavements are changed to white. And, changing to white pavements would be dangerous in areas that get snow and ice in the winter. Drivers would find it almost impossible to see a lot of the snow and ice.
Anyway those areas do have a high albedo in winter, so I guess they could be exempt from any changes.
Vendicar_Decarian
3.7 / 5 (3) Apr 12, 2012
Then they should construct their buildings so that they contain low E windows, and heavy insulation.

In a typical wood frame house, the cavity between the ceiling and the roof is called an attic, and in very cold climates it is recommended that the attic be open to the outside air - to combat condensation. The bottom of the attic should be well insulated with between 12 to 18 inches of insulation who's upper surface is necessarily exposed to the outside air.

Since the attic should be the temperature of the outside air, you can not rely on the roof above for winter heating.

"There are many areas of the world where people want to *retain heat in their buildings, not cool them!" - Peter_Y
Vendicar_Decarian
4.2 / 5 (5) Apr 12, 2012
That would depend wouldn't it?

My roof is white because I chose it as an appropriate "color" from a variety of alternatives - some of which were very dark brown.

The cost of the white roofing was identical to that of all other colors.

"How much CO2 would be released in the production, transportation, and installation of all of this new roofing material?" - DeathTard
Deathclock
1.9 / 5 (9) Apr 12, 2012
Rooftop gardens absolutely increase albedo, because plants and trees increase albedo. "Google" it while you kick yourself in the ass, dunce.


Increase relative to what? Mirror roofs or bright white roofs? Absolutely fucking not.
Telekinetic
1.6 / 5 (7) Apr 12, 2012
Just one of hundreds of scientific papers, dunce-
"It is shown that better results are obtained in calculating the surface albedo of a plant stand for near-infrared solar radiation using the modified two-stream approximation in favor of the Schwarzschild one. These evaluations of the plant stand surface albedo were obtained by assuming the values for scattering parameters of upward 0 and diffusive solar radiation in the plant stand, by applying the delta-Eddington approximation."
hamish_niven
3 / 5 (5) Apr 13, 2012

What is wrong with 10,000 acreas of trees, green tall trees, bushes and shrublands? they absorb so much more C02, the ground below also absorbs all the water that would otherwise flow off the urban sprawl of concrete and pavements.
Rain - all that water has to go somewhere, and roads, pavements etc simply cant cope with the smallest flash flood or bad winter storms.
Its a blinkered narrow minded and utterly contemptably feeble excuse to justify another mall, another development without a soul, the removal of playing grounds for kids, parks and water features for birds, fish and - oh yes its called life, peacefullness and nature,

The article may be perfectly correct, that concrete and repaving reflects the sun a little more than the same surface area of grass / trees etc, but at what price.
Nuclear energy is a fucking amazing, tell that to those who are dying from cancers from nuclear accidents.

is it worth it? all that cost, ugliness and waste?
plant a forest
antialias_physorg
3.5 / 5 (2) Apr 13, 2012
How much CO2 would be released in the production, transportation, and installation of all of this new roofing material?

If you just put it up where roofing material needs repalcement anyways (or on new buildings): none at all.

Chicago has already instituted a program to create green roofs on its city buildings since 2008. Vegetable gardens can be grown, people can be fed,

Any studies yet how healthy food is that is grown in polluted inner city atmospheric conditions?

And if we 'correct' with albedo changes, when emission controls continue to get implemented, do we intentionally pollute more? Or resurface again to try and reverse the effect?

Its not a question of either/or. We should do both. Using this method would just buy us some more time (read: mitigate catastrophic climate events until we have weaned ourselves off fossil fuels)
kaasinees
2 / 5 (5) Apr 13, 2012

Any studies yet how healthy food is that is grown in polluted inner city atmospheric conditions?

Lol, you breathe it in everyday which is more harmful than eating a plant that breathed it in.
antialias_physorg
3 / 5 (2) Apr 13, 2012
Lol, you breathe it in everyday which is more harmful than eating a plant that breathed it in.

That's not the same at all:

- Plants (and animals) tend to concentrate poisons in a different way than simply breathing the air does. Humans, for example, would be considered HazMat at the end of their lives due to al the mercury and whatnot that has accumulated in the liver. This is one reason why it's forbidden to dump the ashes of cremated humans just anywhere. If you were to apply strict substance limitations then you wouldn't even be allowed to dump them on a municipal grabage heap.

- Poisons are taken up differntly through the lungs and the instestinal tracts.

-Particulate matter get washed out of the air when it rains and land on farmland (but not inside your home).

- ...
Au-Pu
1.6 / 5 (7) Apr 13, 2012
Very interesting. But global warming is not a man made phenomena. It is part of a 3 billion year cycle of Glaciations and interglacial periods. Over this time they have developed an average of 41,000 years between glaciations. That does not mean that there is 41,000 years between them because they vary, but their average is 41,000 years.
When you consider that our last ice age was 12,000 to 13,000 years ago it tells you that we have roughly 7,000 to probably 9,000 years of continued warming to go before the Earth starts to cool towards the next Glaciation (Ice age).
So let us get real and hopefully the imbeciles will all crawl back under their rocks and stop bothering real people.
The questions are: Are we accelerating it? I think the answer to that is a resounding YES. Can we stop accelerating it? I feel absolutely certain that we can. Can we undo whatever acceleration we have added? I strongly suspect that the answer to that is NO.
Yellowdart
2.3 / 5 (3) Apr 13, 2012
New York is also going to white roofs I believe.

My question though is, how hard is it to see when these white/mirror roofs are reflecting sunlight back? Anyone have any experience with this? It seems like if every house had one you'd have to wear sunglasses everywhere inside the city. Same problem if your out on the snow for hours with no shades, the light it reflects can damage your eyes. That being said, I wouldn't mind a white roof at all. Not only would it reflect more sunlight, but that lowers your AC bill too!

Lurker2358
2.3 / 5 (3) Apr 13, 2012

What is wrong with 10,000 acreas of trees, green tall trees, bushes and shrublands?


10,000 acres of trees will only sequester a few 10s of millions tons of CO2 over their lifetime.

We are currently producing about 30 gigatons of CO2 per year excess. about 2/3s of this is ending up in the oceans as carbonic acid, and about 1/3rd is going into the atmosphere.
NotParker
1.7 / 5 (6) Apr 13, 2012
Wait!!!!!!!

The sun causes warming???????????

Who knew?
NotParker
1 / 5 (4) Apr 13, 2012

We are currently producing about 30 gigatons of CO2 per year excess.


Excess is an unproven assertion.

Since the warming is natural, some of the 38000 gigatons of carbon stored in the ocean is outgassed since warmer waterholds less CO2.
Straw_Cat
2 / 5 (1) Apr 14, 2012
Redoing the parking lots and driveways with permeable pavers like the ones shown in the link below would change the albedo and remove a lot of water from storm drain systems-- which can save a lot of money operating a sanitary system.
Grow a parking lot, etc, instead of paving it.

http://www.greeni...odwC9zhg
mosahlah
1 / 5 (2) Apr 15, 2012
If global warming is truly such a dire threat to humanity, and not a bandwagon for social engineering.. shouldn't we just scale this up and whitewash the Rockies?
BuddyEbsen
1 / 5 (2) May 01, 2012
This does sound like a low-cost, elegant solution, and please take note that they are talking about a 0.1 increase in albedo, not going to 1.0. They do not say what the current average number is, but I would guess its lower than 0.5 with all the paved roads.

That said, I do wonder if pilots will be blinded when flying over a bright white city on a sunny day.