Save the climate, raise our albedo

Written By: - Date published: 11:06 am, August 10th, 2009 - 16 comments
Categories: activism, climate change - Tags:

Dark material gets warmer in sunlight than light-coloured or white material. Heat energy enters our atmosphere after light strikes the surface of the Earth, is partially converted into heat, which then radiates into the air. White stuff reflects the sun’s energy straight back into space without converting as much of it into heat.

Because of this, melting ice sheets isn’t only a result of climate change, it causes more. Shiny white ice is replaced by darker ground or ocean, meaning more heat entering the climate system. Cities too, with their dark roads, create ‘heat islands’ that contribute to warming the atmosphere.

But what if we made the Earth more reflective? Less heat entering the system, counteracting the heat trapping effect of greenhouse gases, reduced climate change.

It’s actually not that hard.

Just painting the dark roof of a 100m2 house white offsets 10 tons of carbon emissions – over half of average annual emissions per person. So there’s something each person can do at a personal level that makes a real difference.

According to a study, making the roofs and paved areas of the 100 largest cities in the world whiter would have the same effect as the whole world not emitting greenhouse gases for a year – or, put another way, would offset 11 years of emissions growth. Secretary of Energy Steven Chu talks about the concept with Jon Stewart here:

The great thing about this as part of tackling climate change is its simplicity. Every individual can choose to play their part for no extra cost when repainting, repainting, or installing a roof ( more than that, white roofs save money on cooling in summer but don’t increase heating costs in winter). The government can provide leadership very easily just by lightening the colour of asphalt used in state highways. One step further would be providing small subsidies to lighter coloured house paints etc.

Of course, this is just a part of the complete programme we need, NOW, to confront climate change but I think it’s awesome that this shows we can make a difference with simple, clever actions.

16 comments on “Save the climate, raise our albedo”

  1. So Bored 1

    Not so boring at all. Really appreciate the simple little things we can do to offset carbon emmissions whilst the polluters cry foul. Would like to see a local study for NZ houses and conditions, we might need the roof warms to heat our little boxes.

    If it works good….we have just subsidised insulation, How about roof painting? Creates employment, would gobble up some of the unemployed.

  2. Andrei 2

    Of course people in the Mediterranean whitewashed their houses for years now to keep them cool.

    Applying the same technique in New Zealand though would see greater energy consumption since the natural solar heating of our homes with their nice red roofs will be reduced and the shortfall replaced by other energy sources.

    Physics 101 I’d have thought still having boffins fly around the world promoting wacky ill thought through ideas is the way of the 21st century I guess.

    • So Bored 2.1

      You may be right about the other energy sources but you could ask how much roof heat gets into a house that has insulated ceilings?

      On the boffins flying around the world a well spotted trend, wonder how much CO2 goes on conference travel?

    • Andrei 2.2

      Well the fellow wants the roads to be white to.

      Ever had snow blindenss?

      Can you imagine driving on a white reflective road on a bright sunny day?

      • So Bored 2.2.1

        Extra dark sunnies and tinted windows…….gangsta rap gear.

      • Maynard J 2.2.2

        White is reflective of energy – it does not need to be *shiny* to reflect infra-red spectrum energy, only visible light. The two are not the same, nor are they interchangable .This article is talking about reflecting energy, not light. Is that not part of Physics 101?

        • Andrei

          This article is talking about reflecting energy, not light. Is that not part of Physics 101?

          Well no actually

          See if it is reflecting energy then the spectral distribution of the energy reflected will have the same spectral distribution as the incident energy – of course.

          If we are talking about emitting energy then of course it is a entirely different matter. Any body regardless of surface color that is in thermal equilibrium with its environment will be emitting energy in an amount exactly equal the incident energy falling upon it. In the real world any object will be reflecting portion of the incident energy and absorbing another portion. The absorbed portion will be re-emitted with a spectral distribution described by Max Plank’s Black body radiation formula which depends upon the temperature of the body in question but is “favors” if you will the longer wavelengths ie infra red.

          Now of course it is the shorter wavelengths which find it “easier” to escape the planet while the longer wavelengths are absorbed by the atmosphere warming it (the greenhouse effect).

          but the whole purpose of this exercise is to keep the planet cool by reflecting the suns incident energy back into space rather than have it absorbed and re-emitted in the longer wavelengths

          Here endith the physics lesson

      • Eddie 2.2.3

        it doesn’t have to be that bright

    • Eddie 2.3

      apparently, because the sun is low in the sky in winter, it makes little difference what colour your roof is little heat comes into the house from it anyway

  3. Mac1 3

    Interesting idea, Marty G. However, I have had installed a HVS, or home ventilation system, which works as a house warmer by transferring heat trapped in the roof cavity into the house as warm air. My house was a prime candidate as it has a black decromastic tile roof. The temperature of the roof cavity is at the moment 19 degrees and has warmed the house to 18 degrees at midday whereas the outside air temperature is about 16 degrees.
    Yesterday, the house temperature was raised to 22 degrees, purely by solar radiation and the use of a small amount of electricity to power the fan. The house is dryer and air-filtered as a further consequence.

    I wonder what difference that makes to the carbon footprint of this house and its inhabitants, by using the most efficient coloured roof (black) to trap heat than by using a white roof.

    Does that trade off the savings to the individual carbon emissions by painting the roof white, as your post suggests. I know that little heating (via a heat pump) is only required to keep the house warm.
    In summer of course, the roof cavity gets up to more than 50 degrees but insulation in the ceiling mitigates that. As the roof cavity cools after sundown, faster than does the house, cooler air is transferred into the house to force out hotter air. I do not know whether the colour of the roof has any effect on the radiation of heat away from the roof cavity.

    • So Bored 3.1

      Mac, where did you begin with this to get the basic info? I have a house to renovate, sounds like a clever way to do things.

  4. Mac1 4

    So Bored,
    the firm I dealt with is Snug Air Ltd- selling HRV (heat recovery ventilation)-they may be contacted 03 5396124 (Nelson). Otherwise, google HRV and HVS. I first attended a home improvements trade display to alert myself to the system.
    Update- in an hour the house temperature is now 21 degrees, same as the roof cavity, outdoor air temperature is about 18. 🙂

  5. burt 5

    Mac1 & So Bored have just illustrated that one size won’t fit all. However if I paint my roof white would I be able to claim that as a credit against any other emission based taxes?

    However the next question, in modern global warming theories the effect of solar radiation variances due to sun spot cycles is considered inconsequential. CO2 ppm takes more focus for modern (settled…) global warming theories. So how is paining a roof white effecting CO2 production (clue; it is not) and why is this effect being compared with tons of CO2? Clearly the cooling effect from painting a roof white it is a result of reducing the absorption of solar radiation?

    So it’s not the cars eh, it’s the black roads and dark roofs we have been building like crazy for generations.

    • Marty G 5.1

      read the paper burt, it’s actually just a summary, nice easy to follow equations for you

    • burt 5.2

      I get it Marty G. It’s like a religious zealot saying “has science found God” but it is Greenhouse gas zealots saying has solar energy found CO2.

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