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More Reflective Roofs and Pavements Could Help Offset Climate Emissions

Increasing the reflectivity or albedo of roofs and pavements in urban areas could offset greenhouse gas emissions by a significant amount, according to an open access paper published last month in the IOP journal Environmental Research Letters. The research performed by scientists at Lawrence Berkeley National Laboratory and NASA’s Goddard Space Flight Center shows that a 25% and 15% increase in the albedos of roofs and pavements, respectively, in urban areas, could lead to an offset of approximately 57 billion tonnes of carbon dioxide.

Surfaces with high albedo reflect more solar radiation, preventing the radiation from heating the surface and the atmosphere. Introducing “cool roofs” and more reflective paving materials could replace some of the albedo that has been lost through the melting of Arctic sea ice.

Based on the radiative forcing obtained in this study, the potential emitted CO2 offset for a 0.25 and 0.15 increase in albedos of roofs and pavements in urban areas is about 57 Gt of CO2. If the annual cycle was considered in this work, the offset may be lower. Both studies indicate a qualitatively similar response of a reduction in radiative forcing or an increase in total outgoing radiation for an increase in urban albedo and the values indicate an approximate range in potential emitted CO2 offset that may be expected if urban albedos were increased.

—Menon et al.

Increasing urban albedo is something that should be done now to buy time for implementing other near-term and long-term climate mitigation strategies. Although it does not solve the root of the climate change problem—substantial reductions in CO2 and other climate forcers are essential for that—urban albedo can delay the onset of more severe climate impacts, and reduce the risk of passing the thresholds for abrupt and irreversible climate changes.

—Durwood Zaelke, President of the Institute for Governance & Sustainable Development (IGSD)

In addition to increasing urban albedo, other fast mitigation measures that will result in significant near-term reductions to avoid passing the tipping points for abrupt climate change include reducing emissions of black carbon soot, methane, and tropospheric ozone, as well as using the Montreal Protocol ozone treaty to phase down hydrofluorocarbons, which could prevent the emissions of more than 100 billion tonnes of CO2-eq. by 2050.

Carbon-negative measures such as better forest management and production of biochar will also be necessary to bring atmospheric concentrations of CO2 back down to safe levels, according to IGSD.


  • Surabi Menon, Hashem Akbari, Sarith Mahanama, Igor Sednev and Ronnen Levinson (2010) Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets. Environ. Res. Lett. 5 014005 doi: 10.1088/1748-9326/5/1/01400



It sounds like an easy thing to do - but how would you get people to do it ?
Would it only apply to south facing roofs, or all roofs?
What would happen to people who refused to do it ?

I can see how people who have to use air conditioning using it to reduce their bills, but should everyone paint their roofs?

Right now, in Ireland, it is pretty cold (and has been for the last 2 months) and I cannot see too many people signing up to (apparently) make their houses colder (even though, they would probably make them warmer in winter due to less radiative losses.

It would seem to make a lot of sense in the Southern US where it is hot, sunny, and people can afford to use a lot of AC.

I am not sure about making pavements white - it might cause a lot of glare.


Recall that the standard architectural design of most arid and tropical environments is white buildings. White wash exterior walls is the norm in most of the Mediterranean. Taxing people who paint houses dark colors is one, approach. Outlawing dark tar and excessive roofs in warm climates another.

In NYC painting businesses have done well showing landlords how silver painted roofs save $$ in summer cooling costs.

White pavement wouldn't last long.


What about using roofs for micro-generation for solar and perhaps event wind? Ok this may only make a small dent in demand but then it would also help to reduce the need to rpovide additional energy generating capacity elsewhere.

Bearing in mind that solar and wind rely on fluctuating weather, surely this can be smoothed out by using excess power to generate hydrogen in-house for conversion back to electricity later, or perhaps used as gas for home heating.

Perhaps someday someone will come up with a solar / wind array that will also led to home fuel production through chemical conversion of hydrogen and CO2 etc - fancy filling your car up in your garage?

Stan Peterson

And you were wondering what the pollutant effect is from Solar PV cells? Now you know. They alter the planetary Albedo in the WRONG direction. They are the blackest of blacks, since they are active devices, and engineers strive to make them absorb as much of the solar incident energy as possible.

Solar cells reduce the Albedo to near ZERO over every square meter wherever they they are installed. So it is a cumulative effect, and it doesn't matter whether its from a million rooftops, or a few hundred enormous Solar energy farms.

The PV industry likes to advertise that they have created several thousand Square kilometers of such devices; so it is no longer insignificant. Plus the 10-12% efficiency means that they create lots of waste heat of about 88-90%, and so create 'Thermal Pollution' as well.

So the next time some green loon advises you that Solar is 'pollution free', tell him he doesn't know what he is talking about...


Hi Stan,
I was thinking the same myself - a 16% efficient solar cell sucks in 84% as heat.
Has anyone done a study of the relative merits of a white roof vs either solar water heaters or solar PV?
It strikes me that the key is whether you have AC or now - if you have AC, you might be better off painting the roof white - if you don't, it might be harder to call.
Solar water heating seems like a good idea generally.

On the other hand, there is something comforting about generating some of your own electricity, even if you buffer it with the grid.
+ PV seems so much "greener" than just painting the roof. It is a bit like the difference between a Prius and a bicycle.


Wouldn't it be easier to make reflective PV that would absorb 20%-25% of the sun energy (and transform it into electricity) and reflect the other 70%-75% much the same as white or silver roofs do?

A win-win-win condition is possible to make everybody happy.


Duh. Who'd a thought? asphalt pavement gets hot. Dark ashpalt shingle roofs get hot. Amazing.
Some of us are overlooking the fact that the headline says, "in urban areas".


According to the U.S. Department of Energy, in order to provide all of the electricity consumed in the United States, it would be necessary to cover 0.3% of the land with solar panels. This is equal to about one fourth of the amount of land currently covered by roadways. While this is a large undertaking, it is interesting to note that this is approximately the same amount of land currently used to supply fossil fuel and nuclear power to the U.S. when mining is included. The average homeowner only needs to put PV cells on 20-25% of his roof to power his house. However we wont even need this much, renewable power works best when it comes from a mix of sources; solar, wind, hydro, biogas, etc.

For grid stability the solar component would likely be no more than 20% - that's 20% of 25% of the roofs or roadways. You could cover only the area of roofs/roadways you needed for power with PV cells(about 5%), paint the rest white, replant the stripmines with forests and come out ahead.


Here's a question; which would be better - a reflective(re: white) roof, or a living(re: green) roof?



ai_vin has some interesting links. The German combi-power plant looks interesting but may be much too complex in practical application. I agree however that any successful renewable program will require combination of systems.

What should be encouraged is for different environments to design and build renewable systems unique to their needs. Obviously Denmark goes to wind because they lack the solar potential of the American SW or Spain. With the recent announcement from Bloom's SOFC boxes, and their implementation at Google's Mountain View HQ - we will get some real world data on combined renewables. Google has a huge solar array as well as the new SOFCs. They tell us the FC is a far better use of land/area per kWh produced.

We also have wildcards like LENR that demand entire physics re-think, waiting just offstage. The problem I see is the need to "make work" rather than eliminate it (unfortunately from the wizzy POV.) The truly innovative stuff disrupts world economic growth - which is needed.

Stan Peterson

Sorry Harvey. The Physics reality gets in the way of your religious desires. It is by making the PV cells as absorbent as possible that the PV engineers obtain the ridiculously poor 10-12% efficiency that they get. If they do as you suggest, their solar cells would be 1% efficient, as they originally were.

Wouldn't it be wonderful, if you could turn Gravity on or off? Then you could lift a weight high and then gather the "Energy" as it fell. Think of the Energy and perpetual motions machines you could build!

And it doesn't viiolate your religious ideas. Of course, the only reason we don't have that now, is the evil capitalist pigs of 'Big Oil'. They bought the patent and buried it alongside the plans for the 100 mpg carburetor.


CIGS thin film panels can be made on transparent material. The longer wave lengths pass through and are reflected back. There is no violation of physics there.

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