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White, reflective roofs

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Stephen Scholle

Oct 28, 2011
11:13

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As white snow cover disappears white roofs and reflective roadways and parking lots would help mitigate solar absorption. Has there been a quantitative study on the potential for that kind of conversion? What are the political and economic hurdles involved?

James Greyson

Oct 29, 2011
03:45

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Hi Stephen, white roofs is part of this proposal in the CoLab: Cycling Carbon by dennis https://www.climatecolab.org/web/guest/plans/-/plans/contestId/5/planId/15108 It suggests a potential equivalent to 57Gt C and includes links to further info. Snow cover offers 2 services for incoming solar energy, reflection and absorption (when melting). White roofs can of course replace only one of these. The melting process also includes permafrosts and methane clathrates (http://en.wikipedia.org/wiki/Methane_clathrate#Methane_clathrates_and_climate_change ) for which there isn't a suitable choice of colour paint to replace ;-) I'm amazed there is not more discussion about the loss of these climate buffers and the positive feedbacks being triggered. This would seem to be a good test for any proposed climate policy; whether it has the potential to quickly stop or reverse these melting (and runaway feedback) processes? James "White Roofs According to Energy Secretary Stephen Chu, if the 100 largest cities in the world converted to white roofs and lighter-colored pavement, it would offset 57 gigatons of carbon emissions. (Details) To motivate these actions, we should apply tax incentives, at the national level with income tax credits (much like solar incentives) or the local level by varying property tax rates. It may also be helpful to pass ordinances overruling homeowner's association rules. Many U.S. cities have been ahead of the federal government on climate change issues, so local action could happen more quickly. White Clouds A fleet of wind-powered ships, spraying small droplets of seawater into the air with technology similar to inkjet printers, could seed clouds and cool the globe dramatically at surprisingly low cost: about $10 billion to counter all current warming. Developing the program could take as little as five years. (A recent study is a bit less optimistic about countering all emissions, but still concluded that the method would work.) Oddly enough, while most people don't bat an eye at painting roofs white, many object to cloud seeding, calling it "geoengineering." But what's the difference? Both are localized actions at low altitudes, designed to reflect sunlight to space. Cloud seeding has the advantage of being more easily reversible. Stop doing it, and the clouds return to normal in a week or so. If for some reason you wanted to get rid of your white roofs, it would take a lot more effort. The U.S. has the world's largest navy and a large merchant fleet; if any nation can build and run a fleet like this, it's America. At a $10 billion pricetag, it's easily affordable."

Don Wilkins

Oct 30, 2011
08:55

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What about "green" roofs? If large roof areas were covered in plants using hydroponics, roofas would be cooled, pants would absorb CO2 and produce could be used year-round. I know in Chicago there was an effort to build a green roof but I have not heard anything about it recently. Are the costs of building and operating too high?

Brian Chow

Apr 16, 2012
07:57

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I tried to gain permission from my city to paint my roof white, but they would not let me. It has been documented that white roofs can lower the temperature on the roof by 40 to 50 degrees Fahrenheit. This has enormous implications, but I don't see why local decision-making authorities aren't buying it. The raw ingredient - titanium dioxide - is not very expensive at all. There's plenty of that to go around, but the politics needs to steer clear of excuses.

Mark Hurych

Jul 10, 2012
01:53

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Painting or misting seem to be narrowly focused on temperature only. Willie Smits managed to change the climate by reforestation. Fish farming in Veta La Palma Spain is cleaning the water while providing biodiversity resilience and good food. I think it's possible to save two birds by not throwing a stone. The current extinction episode and pitiful state of living for too many humans must be addressed together. Without better management of fresh water and ecosystem services we won't be much more comfortable and safe for the future, even with better climate. We have seen European companies reforesting Northern Africa and Permaculture concepts have flourished. These kinds of projects need to go viral and need to be scaled up. We are killing ocean biodiversity by dumping nitrates.

James Greyson

Jul 17, 2012
06:22

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Great to see the list of possible actions piling up! For roofs: white reflection, green living roof or energy harvesting (heat, PV or hydrogen http://cleantechnica.com/2012/06/09/titanium-dioxide-could-lead-to-low-cost-solar-and-fuel-cells/ ) For land around buildings: ecological recovery. Any other ideas?

John Dugger

Nov 23, 2012
05:48

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Requiring reforestation of parking lots would not only improve the looks of urbanization but also reduce the heat island of developments greatly.
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