Climate Change

Published on June 4th, 2014 | by Christopher DeMorro


White Roads Could Help Reduce Urban Temperatures

June 4th, 2014 by  

Long Road

There is no doubt that the coming decades will present a multitude of climate-related issues humanity has to figure out, including how to grapple with rising temperatures. The growing multitude of mega-cities will lead to even higher temperatures in densely-populated areas, though white roads could lead to much cooler temps.

That’s the concept behind the Cool Change Cities Project, which has begun testing a lighter-pigment road surface in Sydney, Australia. This whiter road could drop temperatures in packed urban areas by 7°C, or about 44°F, a tremendous drop in places like Sydney that are experiencing record high summer temperatures.

By creating a paler surface than the blacktop asphalt we’re all used to, project designer Michael Mobbs says that much of the overnight heat that seems to linger will dissipate thanks to his “cool roads” idea. By mixing in rocks, concrete, or other pigment-altering substances, roads can be made to look more white than black.

Traditional blacktop roads are increasingly seen as problematic as they absorb daytime heat and slowly release it overnight, keeping temperatures artificially high. Mobb’s “cool roads” wouldn’t absorb nearly as much sun, as their pale complexion would reflect much of the sunlight right back into space.

This solution can be applied to more than just roads though; many homes and buildings still use black shingles on their roofs, and in heat-struck Australia, this no longer makes much sense. White roofs have already been tested with great success in places like New York City, and Mobb thinks he could lower the average temperature of all of Australia ( or at least the populated parts) cooler by 2°C. An ambitious goal for such a simple solution, but it certainly sounds plausible. Thoughts?

Source: Renew Economy

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About the Author

A writer and gearhead who loves all things automotive, from hybrids to HEMIs, can be found wrenching or writing- or else, he's running, because he's one of those crazy people who gets enjoyment from running insane distances.

  • Something obvious that they seem to be overlooking – car tyres are black, and they quickly make roads that aren’t black, black through rubber transfer. There are areas of road with red and green bitumen here on the freeways and they have large areas of black on them, and that’s just freeways, where cars are not turning and scrubbing tyres due to direction change forces. White suburban roads would need regular cleaning, which would be impractical.

    Here in Oz, it would make a lot more sense to just stop the ignorants in the building industry from using dark coloured roofing materials, they do it all the time and the dopey general public don’t know any better so they don’t ask for lighter colours.

  • Bob_Wallace

    White roads might need some more study before we move to them. Looking at the results of a study of white roofs in urban areas –

    “Jacobson’s computer modeling concluded that white roofs did indeed cool urban surfaces. However, they caused a net global warming, largely because they reduced cloudiness slightly by increasing the stability of the air, thereby reducing the vertical transport of moisture and energy to clouds. In Jacobson’s modeling, the reduction in cloudiness allowed more sunlight to reach the surface.

    The increased sunlight reflected back into the atmosphere by white roofs in turn increased absorption of light by dark pollutants such as black carbon, which further increased heating of the atmosphere.”

    • Omega Centauri

      The main benefit is the urban microclimate, and reduced energy needs for cooling. Urban landscapes should also need a bit less water at lower temps. In some climates, such as California, you simply don’t get summer convective clouds, so Jacobson’s efect would never come into play.

    • Benjamin Nead

      Well. yeah, I just clicked the link and read that article, Bob. I noted that the study didn’t take into account the reduced use of electricity (ie: air conditioning) that white roofs can have. Therefore, I think it’s a seriously flawed study.

      Also . . . white roofs are common in desert towns and have been so for decades. It really does keep structures cooler, allowing for less AC (both excessive alternating current and air conditioning.) Anyone who purposely chooses a dark roof around here is, well . . . kind of looney (I’ve also never understood the fascination some have with black painted cars down here. You instantly make your vehicle 5 to 10° hotter on the worst sort of summer days . . . running the air conditioning more and, as a result, burning more fuel.)

      And . . . the Jacobson study seems to fly in the face of almost every conclusion I’ve read regarding polar ice cap melting that exposes more dark ocean water and, thus, exacerbates the warming situation. Would Jacobson paint the polar ice cap black to bring on more clouds? It simply doesn’t make sense.

      White roads would certainly help with the urban heat island effect. But roads tend to get grimy and dark fairly quickly. Thus, any cooling effect that they might have when new would be quickly diminished. Roofs, on the other hand, stay whiter for far longer.

      • Bob_Wallace

        Just sayin’ that things are a bit more complicated than “white is good”.

        • Ronald Brakels

          Working out the exact effects is pretty complicated but there’s no doubt that a light roof is better than a dark roof, and that goes for roads too, for at least the bulk of humanity, especially in areas where temperatures get high enough to directly kill people, such as India, Australia, heck – even Russia at times these days. Now maybe there are strange and cold places where dark roofs and roads are better, but they would be far away from where I am currently.

          And of course solar PV is even better than white roof and white roofs can improve the output of rooftop solar by lowering the temperature of the system.

  • Omega Centauri

    What do drivers think of it? Does the extra glare matter to them?
    7C seems like a bit of a stretch to me, I would have expected maybe 2C locally, if its really 7 it is a big result. Wish my horribly hot town would do this.

  • Offgridmanpolktn

    Would seem to be common sense, but what are the costs of installation and extended maintenance, and has the use of the solar panel road tiles been considered /compared? Australia would seem to me to be a great place to use these because the snow melt heaters can be left out and the power fed into the grid.
    Would love to see a remake of the Mad Max movie with the gangs fighting for control of the stretches of highway to keep their electric hot rods and motorcycles moving. And the different light shows that could be accomplished with the incorporated LED’s would make for some wonderful cinema if handled by the right director.

    • Ronald Brakels

      We’re not likely to get solar roads in Australia for a couple of reasons. Since there is no snow to melt there is less advantage to having road surfaces connected to the grid. Also, road solar would provide utility scale solar which has a hard time competeing with point of use solar in Australia. But glasscrete road surface modules might be a great way to make lighter coloured roads at a reasonable cost if asphalt keeps going up in price and the full cost of carbon emitted from cement production and transport is added in.

      But converting Mad Max to solar could work. The line, “The juice, the precious juice…” could refer to current.

  • Cowboyleland

    Um . . 7 degrees C is 12.6 degrees F.

    • Omega Centauri

      Obviously the author just plugged in a C to F converter (or perhaps some automatic software did it automatically). I see this error all too frequently, a consequence of too much uncritical reliance on computers.

    • Manual Math

      Um, wrong: 7°C×9/5+32 = 44.6°F

      • Bob_Wallace

        The article is stating a 7°C increase in temperature.

        Not that the ambient temperature is 7°C.

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