UCAR: Roof white out helps UHI

I find it humorous thatUCAR had to resort to modeling to prove something that can be measured empirically. But then again this is UCAR, and they have a big computer at their NCAR office. Painting roofs white would probably help cool NOAA weather stations that are positioned on rooftops, like this one on the roof of the Santa Ana fire station in southern California, with surroundings that look a lot like the photo provided with the press release shown below. – Anthony


Santa Ana Station looking North.  Click for a larger image

Computer model demonstrates that white roofs may successfully cool cities

January 28, 2010

BOULDER—Painting the roofs of buildings white has the potential to significantly cool cities and mitigate some impacts of global warming, a new study indicates. The new NCAR-led research suggests there may be merit to an idea advanced by U.S. Energy Secretary Steven Chu that white roofs can be an important tool to help society adjust to climate change.

But the study team, led by scientists at the National Center for Atmospheric Research (NCAR), cautions that there are still many hurdles between the concept and actual use of white roofs to counteract rising temperatures.

painting white roofs

A construction crew works on a white roof in Washington, D.C. (©American Geophysical Union, photo by Maria-José Viñas. Reproduction permitted with credit.)

“Our research demonstrates that white roofs, at least in theory, can be an effective method for reducing urban heat,” says NCAR scientist Keith Oleson, the lead author of the study. “It remains to be seen if it’s actually feasible for cities to paint their roofs white, but the idea certainly warrants further investigation.”

The study is slated for publication later this winter in Geophysical Research Letters. It was funded by the National Science Foundation, NCAR’s sponsor.

Cities are particularly vulnerable to climate change because they are warmer than outlying rural areas. Asphalt roads, tar roofs, and other artificial surfaces absorb heat from the Sun, creating an urban heat island effect that can raise temperatures on average by 2-5 degrees Fahrenheit (about 1-3 degrees Celsius) or more compared to rural areas. White roofs would reflect some of that heat back into space and cool temperatures, much as wearing a white shirt on a sunny day can be cooler than wearing a dark shirt.

The study team used a newly developed computer model to simulate the amount of solar radiation that is absorbed or reflected by urban surfaces. The model simulations, which provide scientists with an idealized view of different types of cities around the world, indicate that, if every roof were entirely painted white, the urban heat island effect could be reduced by 33 percent. This would cool the world’s cities by an average of about 0.7 degrees F, with the cooling influence particularly pronounced during the day, especially in summer.

The authors emphasize that their research should be viewed as a hypothetical look at typical city landscapes rather than the actual rooftops of any one city. In the real world, the cooling impact might be somewhat less because dust and weathering would cause the white paint to darken over time and parts of roofs would remain unpainted because of openings such as heating and cooling vents.

Keith Oleson

Keith Oleson. (©UCAR, photo by David Hosansky.)

In addition, white roofs would have the effect of cooling temperatures within buildings. As a result, depending on the local climate, the amount of energy used for space heating and air conditioning could change, which could affect both outside air temperatures and the consumption of fossil fuels such as oil and coal that are associated with global warming. Depending on whether air conditioning or heating is affected more, this could either magnify or partially offset the impact of the roofs.

“It’s not as simple as just painting roofs white and cooling off a city,” Oleson says.

More cooling for certain cities

The research indicated that some cities would benefit more than others from white roofs, depending on such factors as:

  • Roof density. Cities where roofs make up more of the urban surface area would cool more.
  • Construction. Roofs that allow large amounts of heat from the Sun to penetrate the interior of a building (as can happen with metal roofs and little insulation) are less effective in cooling outside temperatures when painted white.
  • Location. White roofs tend to have a larger impact in relatively warm climates that receive strong, year-round sunlight.

While the model did not have enough detail to capture individual cities, it did show the change in temperatures in larger metropolitan regions. The New York area, for example, would cool in summer afternoons by almost 2 degrees Fahrenheit.

A new technique

The study team used a new computer model, developed by Oleson and colleagues, that is designed to assess the impacts of a changing climate on urban populations and explore options for countering rising temperatures. This urban canyon model simulates temperature changes in city landscapes, capturing such factors as the influence of roofs, walls, streets, and green spaces on local temperatures. Oleson has successfully linked it to a computer simulation of worldwide climate, the NCAR-based Community Climate System Model, thereby enabling researchers to study the interactions between global climate change and urban areas.

The new model does not yet have the power to replicate the architecture and design of specific cities. Instead, the research team created abstractions of cities in the model, using classes of population density, urban design, and building construction. Oleson and his colleagues plan to continue refining the model to provide more information for policymakers concerned about protecting urban populations from the risks associated with heat waves and other changes in climate.

“It’s critical to understand how climate change will affect vulnerable urban areas, which are home to most of the world’s population,” says NCAR scientist Gordon Bonan, a co-author of the study.

About the article

Title:
The Effects of White Roofs on Urban Temperature in a Global Climate Model

Authors:
Keith Olson, Gordon Bonan, Johannes Feddema

Publication:
Geophysical Research Letters

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130 thoughts on “UCAR: Roof white out helps UHI

  1. It will help global warming by reducing temperature by 0.0005C over a century whereas natural cooling cycles will do much more, as well as bring misery as cold always does.

  2. Being a former construction inspector I can tell you working on white roofs is difficult for the eyes. It’s like walking in a snowfield and the effect is blinding and extremely hot as the sun and roof reflection can make life miserable.

  3. Okay…I’ll state the obvious….what is a NOAA weather station doing on top of a black tar roof. And they wonder what is causing the global warming.

  4. It could probably be very helpful and cost-effective. So it probably will not be done.

    I am reminded of Civil Defence studies in the UK during the 1950s. If a nuclear bomb were to airburst directly over a point there isn’t much you can do for the people beneath. But many miles out the flash can set fire to combustible objects like curtains and furniture. Brick houses and tiles, as are common in the UK are quite resistant to this, but the windows will let the light and heat in.

    Running studies and simulations (not computer – real!) it was discovered that the most practical and cost-effective civil defence action was to paint your windows white. Most Britons have an old pot of white paint in their sheds, so it would be effectively free, and this would save many thousands of deaths in house fires around the periphery of a nuclear attack. So that advice was put in 1950s civil defence pamphlets.

    CND joyfully made a major attack on the ‘stupidity’ of defending yourself against nuclear attack with a pot of white paint, and set the pamphlets up as a national joke. If I recall aright, they were withdrawn and never released.

    I was very young at the time, but wondered why people should actively reject advice which made a lot of sense to me. I was obviously too young to understand politics…

  5. What is wrong with these people they keep reinventing the wheel. It is well known fact that white or light coloured roofs prevent heat gain in buildings. Fine when its hot the building uses less air conditioning however in the winter the reflection of the heat will require more central heating.

  6. Have a look at pictures of Bermuda, most of our roofs are made of stone, we keep the roof’s clean and white washed as they are used to collect rainwater to store in tanks under our houses. The 12,000 gallon tank under our house is considered small!

  7. This is so sad. There are certain aspects of the natural world which cannot be readily measuded so we attempt to produce mathematical models to explore them hypothetically. However this would have to be one of the easiest things to set up and experiment to test but they haven’t yet gatherd ANY data. Must really like the inside of thier offices.

  8. Better “Hot tin roofs” (without the cat of “A cat on a hot tine roof”), they reflect more sun rays.
    Seriously, these global warming scientists have their heads too warm, they need high albedo hats.

  9. Now i understand climate science. It’s a sequel of Monthy Python’s flying circus. Our computer model shows that it could help. But we gotta do some more research to see whether it’s feasible. It’s not as simple as painting the roofs white. No, sure not, otherwise you wouldn’t need that honkin big computer, would ya? Oh, and you gotta do even more complicated models? My, my. Ministry Of Silly Walks.

  10. And what would the cost be? And how much CO2 would be produced in the manufacture and distribution of the paint? And how do you paint over asphalt and gravel roofs, etc., etc.?

    What is obvious is that there is far too much money going to research and these guys are just looking for ways to spend it. Time to cut back on research money and let the scientists fight it out by prioritizing their research.

  11. Sigh, will their drivel never cease? They used a computer model to come up with “white paint will have a cooling effect”?? Really? Wow!!! One has to wonder what they’ll come up with tomorrow. Maybe something along the lines of “Computer models show that it is typically cooler at night than during the day!!!!”

  12. It seems as though these folks are obsessed with cooling which only applies in some climates. Do they have a clue as to how much heating energy (fossil fuels) is saved during the winter in other climates when the sun beating on the structure reduces the load on the heating system?
    I agree that this may be effective in warm climates, but how about the rest of the planet. I realize the model is not so simple since the roof emmits energy to the atmosphere during the night that varies according to the color and texture of the roof.
    I have the best of both worlds with my house since it is virtually surrounded by trees. In the summer, the trees keep the house cool, in the winter the leaves are gone and the sun heats the house.
    Of course by studying this there is an admission that CO2 is not the only important factor. If this would get them off our back, I love the idea.

    Of course it is stupid to collect temperature data on a hot black roof anytime of the year.

  13. Does this mean that blondes are cooler than brunettes?

    At the end of WW2 my father had the job of painting coal with whitewash. Really! There was a logical reason – nothing to do with keeping it cool.
    See if you can guess what it was.

    Reply: Preventing the spread of coal dust? ~ ctm

  14. So it would be a Mirror’s Edge kind of world. I hope they paint some bits red so you know where you can duck/tumble/leap as you avoid the Green Police…

  15. Reflective metal surfaces are much better, both at keeping buildings cool (which is why they are very popular in Australia) and reflecting the sunlight back out to the upper atmosphere and space.

  16. Next, they will be painting the deserts white. How childish. haven’t they figure it out yet? Clouds are a much better alternative.

  17. summer white paint to cool the building by reflection, winter in black paint to warm the house, help paint industry, provide more jobs, win win situation !

    If steve chu is serious about the roof color, he just provided the half solution :-)

  18. To work, this requires a paint that (1) has low emissivity (2) is resistant to weathering and (3) can withstand the frequent cleaning necessary to maintain that low emissivity.

    Does NCAR recommend a coating to use?

  19. At least they actually admit UHI. But how much energy would it take to make the paint and apply it and how much pollution would be produced? I guess it would create some of those so called green jobs we keep hearing about.

  20. Climate Science:
    (1) Make a graph.
    (2) Connect the end points.
    (3) Is it very flat? Yes -> Go to (1)
    (4) The line is not too flat. Extend the line for 200 years.
    It goes way up or down, yes?
    (5) Publish.
    (6) News Release: Computer model predicts disaster within 200 years.
    (7) Threaten to smear businesses unless they show enlightened, unbiased support for your continued research.
    (8) Collect grant money for further studies.
    (9) Found a non-profit research institute for the good of mankind.
    (10) Pay yourself $150,000+ out of the non-profits.
    (11) Smile -> Go to (1)

  21. Need to balance the ‘benefits’, (debatable), against the additional drain on the rather limited known economic reserves of titanium dioxide (~130 yrs at current consumption?).

  22. You can also increase cooling by increasing the surface area.

    Billions of tetrahedrons, p’raps made from recycled car tyre rubber and painted white, dropped on onto roofs by helicopters.

    Science, it’s not difficult.

  23. Sorry to to OT. I just spent some time browsing Obama’s new climate site. If you don’t mind feeling extremely nauseous, take a look at it at http://www.climate.gov

    “WASHINGTON — US President Barack Obama’s administration announced plans Monday for a new office handling climate change, aiming to help businesses chart future plans as the nation shifts to a greener economy.

    The first practical effect was the creation of a website, http://www.climate.gov, which came online Monday and brings together government resources on climate change for business, scholars and the general public.”

  24. In 1987, the company I worked for had a new roof put on. It had a “Hi Tec” rubber membrane in addition to the traditional tar. The final step was to apply a WHITE urethane foam coating to reduce heat absorption.

    There is nothing new under the Sun it seems.

  25. I can see the point if it saves on aircon bills, but not if it increases heating bills.

    But, the paper does not address this obvious question, as it is too diffuse and altogether at the wrong scale to be of any worth. If this computer modelling exercise was funded by the public, I’d say they have a case for a refund. Nothing personal you understand; it is just a quality thing.

  26. “I find it humorous thatUCAR had to resort to modeling to prove something that can be measured empirically. ”

    Without at least a little bit of modeling, would you have any idea how much effect it would have on a city? At some point, one has to do a few calculations.

    REPLY:
    Modeling with real world data after you’ve measured the effects on a few urban roofs would be the logical progression of events. There’s no mention of measurement of any kind. Measurement trumps modeling when seeking before and after effects. -A

  27. 1) “at least in theory, ”

    If my aunt had testicles, she’d be my uncle … at least in theory.

    2)“It remains to be seen if it’s actually feasible for cities to paint their roofs white, but the idea certainly warrants further investigation.

    Translation A: Give me more grant money.
    Translation B: I am retiring in 4 years. I may be able to carry this project through until 2014 after which I won’t care.

    Bah!

    Clive the Canuck Cynic

  28. And city roofs constitute what proportion of a city’s surface area?…………

    And what proportion of the earth’s surface?……………..

  29. I am a roof consultant and the subject of white roofs has been studied extensively for a number of years. California enacted Title 24 which requires new roofs have a surface with minimum reflectance and emittance values. Columbia University wrote an excellent paper for New York City on the subject. They calculated the cost of various actions including white roofs, more trees, vegetated roofs, etc. The paper is called Mitigating New York City’s Heat Island with Urban Forestry, Living Roofs, and Light Surfaces.

    Chicago tried to enact a law requiring white roofs, but they’ve had problems. Oak Ridge National Laboratory wrote a computer program that calculates energy savings under different scenarios. In northern cities like Chicago, the dark roof surfaces actually save money because of the heat gain during winter months.

  30. Off Topic: Guardian still letting its guard down – well just a little…
    Here anonymous IPCC wkg gp 1 writers complain about the invasion of social sciences method (of wkg gp 11) into their domain of hard science. And then we get this nice assessment of the situation:

    “This is a transient and manufactured crisis and will likely go away with time,” one IPCC author said. “What the science community needs is a few huge donors to throw millions of dollars behind PR campaigns to counter the propaganda out there. We are being attacked through baseless smear campaigns and we are not PR experts.”

  31. “RJ (13:58:28) :

    Sorry to to OT. I just spent some time browsing Obama’s new climate site. If you don’t mind feeling extremely nauseous, take a look at it at http://www.climate.gov

    Love it. Now all we have to do is find mistakes and ridicule them.

  32. Don’t know if anyone mentioned or asked this question, but the roofs of buildings is not the only part of the building warmed by the sun, is it?

    What if the entire building was painted white? How about the parking lots, sidewalks, and streets?

    Oh, and all vehicles should be white, too.

    And, people should all wear white clothes.

    And all the signs should be white.

    And …

  33. I recommend a trip to e.g. Spain, or Greece.

    They must have had some excellent ancient supercomputer there that with the help of new (old?), sophisticated, state-of-the-art modelling taught them to paint their houses white.

  34. A few groups are actually working on roofing materials that change from light to dark depending on the temperature, so it is more reflective in summer and less reflective in winter.

  35. KeithGuy (13:43:13)

    Painting coal…

    No need for a reason, standard Army rules before an inspection. If it moves oil it, if it doesn’t paint it.

    Also no signs of safety precautions for the people up on that white roof. Looks like a power cord dragged up the side of the building, tied round the vent and laid across the roof as a trip hazard. We try not to let the ‘elfin safety’ types bully us over here but they might have a point with that one.

  36. I’m so sick of money being wasted in climate science. If this was publicly funded, then I hope you are all disgusted by this egregious waste of tax dollars.

    Look at Michael Mann. Prior to his hockey stick, we all knew the Medieval Warm Period and Little Ice Age existed. We have a mountain of evidence across a dozen disciplines of science. But Mann had to “contain” it and get rid of it. In 1998 he published and apparently he believed that temperatures cooled for thousands of years and then shot up drastically. It took him until 2009 to “discover” the MWP.

    That is 11 years of time and millions and millions in tax dollars wasted on “discovering” something we already knew!

    Combine this with our current regime, err, government’s spending habits – ie, Pelosi spending hundreds of thousands on alcohol and food for entertainment – and it all starts to make sense. The government wastes our money, so they want these fraudster scientists to publish papers that make global warming look like a real threat. They can then use this fake data to get cap and trade passed which allows them to tax us more.

    So they are wasting our tax dollars to do science that lets them tax us more.

    [snip]

  37. “berniel (14:10:54) :
    […]
    “This is a transient and manufactured crisis and will likely go away with time,” one IPCC author said. “What the science community needs is a few huge donors to throw millions of dollars behind PR campaigns to counter the propaganda out there.”

    Yeah that’ll help. Look at the BBC science/enviro page today. They went into propaganda overdrive. 4 or 5 climate change articles up.

  38. @DirkH
    “Now i understand climate science. It’s a sequel of Monthy Python’s flying circus”

    Dirk – we think alike. Have a look at the Village Idiot sketch.

    Watch for the absolutely priceless lines at around 2:40

    “Mr Figgis is no ordinary idiot, he is a lecturer in idiocy at the University of East Anglia”

    They actually bestow mud on the new graduates!

  39. White paints are made either from lime –water based, good for walls but not too good for roofs. Or made with titanium pigments, as in sun blocking creams. Both products come from mining and especially lime, those processes are big CO2 emmiters.

    It boils down that what you save on heat and fuel will be put again into the atmosphere by lime manufacturing and titanium mining.

    It is like swapping a $500.000 dog for two $250.000 kittens. But they will be creating “jobs” Ha!

  40. “Cities are particularly vulnerable to climate change because they are warmer than outlying rural areas.”

    Cities can have “climate change”, yet the MWP was “regional”????!!!

  41. “Andy Scrase (14:29:30) :
    […]
    “Mr Figgis is no ordinary idiot, he is a lecturer in idiocy at the University of East Anglia”

    Priceless. Begs the question: Was the UEA’s reputation already that bad back then?

  42. Agree that this is being done in a silly way by UCAR. Also second the questions about using solar panel arrays to intercept the light. Developing that point (and the changeable color idea, above), has any of these people ever used a tent fly? It would be interesting to try a white fly that is mounted over a black roof; the fly is used for hot months, then taken down in colder ones so the roof can soak up the energy. If you oriented the fly, you might even get some useful convection effects? Admittedly this is finicky, labor-intensive (although we might see some good innovation with self-furling sails etc.) and a fly might blow out or be baked to shreds in a few years. Still, I’m curious.

    And Cristo would have a ball with the aesthetic.

  43. “has the potential to significantly cool cities”
    A. still convinced it’s warming
    B. still convinced they can control it

    “there are still many hurdles between the concept and actual use”
    A. can’t find a scientist that can paint??
    B. need a grant to study it first

  44. “Painting roofs white would probably help cool NOAA weather stations that are positioned on rooftops,….”
    Anthony Watts
    ————————
    “Our research demonstrates that white roofs, at least in theory, can be an effective method for reducing urban heat,…”
    UCAR
    ———————
    Oh the irony and hypocracy! UHI effect, PRWE (painting roofs white effect), PWWE (painting walls white effect – well known in the tropics).

  45. Now let’s see. Lord Monkton assesses how much paint may be required and its costs. Most paints today are based on Acrylic resins. The resins are synthetic polymers derived from Acrylic acid, which in turn is derived from Propylene — a byproduct from oil refineries. How much extra petroleum needs to be refined to produce paint? But that means more CO2 in the atmosphere, doesn’t it?

  46. Isn’t that a York Air Conditioner condensing unit partly visible to the right of the thermometer on the roof of the Santa Ana fire station? And what are those vents on those units to the left?

  47. Maybe white roofs in Texas….and then gray up towards the North, and finally black in Canada. Would look nice from space!

    hehe.

  48. Off Topic (but hopefully interesting)

    Littlejohn at Desmogblog is making a huge song and dance about Deep Climate’s expose of M&M’s Hockey Stick demoltion.
    I have spent quite a lot of time trying to read through this and quite frankly, it seems to be absolute rubbish. I’m sure this guy has lost it big time, or am I missing something?
    Interestingly though, I left a very critical comment which has been posted, yet completely ignored by their little club.
    Perhaps they failed to understand it was critical.

  49. This is technology is at least a couple millenniums old. applied frequently on Mediterranean architecture, commonly used on Spain, Italy, Greece, Morocco etc.
    No paint is used, instead a mixture of sand, marble powder, quicklime (CaO) and water. This mixture produces a paint like product used to paint walls and roofs in white. The use of this product is not only for decoration purposes, but to reduce heat absorption also allows the walls transpiration, avoiding humidity to build up on them, which is very useful near the coast.
    http://www.graymont.com/applications_history_lime_mortar.shtml

  50. KeithGuy (13:43:13)

    Painting coal…

    OK, Keith, you’ve kept the turkeys in suspense long enough….

    REPLY: I think it was for dust reduction. The calcium carbonate would form a thin shell. Coal dust explosions can be a problem. There’s also a mention that is was used as a theft deterrent, much like odd color spare tires on rental vehicles. – Anthony

  51. someone mentioned putting a reflective metal on the roof, that would work, but.. i live under a major airlane, planes go over my house couple of times an hour, and quite low. could that have an effect in the atmosphere?

  52. We would need an international panel deciding the gray-scale based on lattitude …..hmmmmm

    International Paint Commission Conglomerate ?

  53. Stacey (13:32:00) : “Sorry the point is already made. I should have read more carefully.”

    The point was easily missed, since they seem to be underplaying the problem of lower solar heating in winter. I was looking for that specifically, and it still took a while to find.

    I studied this sort of thing about 50 years ago. You need a coating that is white in summer and black in winter. Any ideas?

  54. Please don’t scream.

    Al Gore Climategate Downfall

    [snip – we don’t post the Hitler parody videos here for the same reason we don’t like being associated with holocaust deniers]

  55. I don’t know how common it is, but many larger buildings in Boulder have the AC units on the roof. Having a surface that doesn’t get as hot before reflecting or emitting solar energy back in the summer would be a good thing on these buildings. Winter sun is not very high, I don’t believe roof color, on a typical commercial flat roof would have all that much effect on heat gain. Plus if the climate is cold enough for that to be an effect one would hope there is roof insulation that would cancel it out. I would expect that the greatest effect is seen in reducing the local heat island effect around big AC units. Its the kind of conservation principle I’d always favor.

    But studying things only with computer models? I believe that is how the idea of catastrophic warming cascades took hold and it is a generally dumb way to approach things. Models will always have simplifying assumptions and one needs to measure and test and retest as more measurements can be taken that the assumptions are valid.

  56. Well thank goodness for computer MODELS. Clearly it must be true then. I wonder if NCAR has considered telling the Mediterranean folk what their models have “discovered”.

  57. Jack Hughes (14:44:59) :

    “Can’t we just wear tin-foil hats again ?”

    I took mine off three years ago, and look at what’s happened! I’m with you.

    “Cities are particularly vulnerable to climate change because they are warmer than outlying rural areas. Asphalt roads, tar roofs, and other artificial surfaces absorb heat from the Sun, creating an urban heat island effect that can raise temperatures on average by 2-5 degrees Fahrenheit (about 1-3 degrees Celsius) or more compared to rural areas. White roofs would reflect some of that heat back into space and cool temperatures, much as wearing a white shirt on a sunny day can be cooler than wearing a dark shirt.”
    How does this square with the various adjustments made for UHI in surface temperature measurements?

  58. KeithGuy (13:43:13)

    Painting coal…

    The answer.

    You paint it to make sure that no one nick’s it. If you paint it white, and it is disturbed then there is this huge black hole, visible to all.
    They you check all the local coal holes for someone with white paint on their coal. then it is time for the plod.

  59. Charles Barnard (13:32:48) : collect rainwater to store in tanks

    Thief! That sort of anti-social eco-corrupting behavior can get you thrown in the dungeon in some of our states in the USA. Washington, Colorado, and Utah are examples. There may be others.
    —————————-
    On topic: On multi-story buildings the overall effect internally will be small and as roof tops are of little extent on Earth the world wide increase in albedo will be small. In most cities the area covered by streets and parking lots is large but the same issue as above applies. Regardless, this scheme, if paint is used, will have undesired side effects. Solar collecting paint or panels may find some use.
    My own suggestion is to spray the roof tops with ocean water and as the water evaporates it will take up energy and cool the surroundings. The collected minerals could be processed and used, especially the salt as it will be needed to clear the streets and highways of ice as the climate cools.

    Ocean Water and Its Wonderful Potential
    http://www.terrapub.co.jp/e-library/dow/pdf/chap2.pdf

  60. I seem to recall the Obamastration talk earlier about forcing white roofs.

    I doubt that they considered what that would do to snow loads and retarded melting time on our high altitude Colorado homes.

  61. jorgekafkazar (15:23:26) : wrote

    Stacey (13:32:00) : “Sorry the point is already made. I should have read more carefully.”

    The point was easily missed, since they seem to be underplaying the problem of lower solar heating in winter. I was looking for that specifically, and it still took a while to find.

    I studied this sort of thing about 50 years ago. You need a coating that is white in summer and black in winter. Any ideas?

    Brown roofs.

  62. The full article “The Effects of White Roofs on Urban Temperature in a Global Climate Model” is behind a paywall.

    The scientists involved are tooting their own horn in public, but are publishing in semi-private. So, I would have to pay to check if they have published their data, methods, and computer models. I don’t trust scientists who tout their results and claims, before a second and third group has given the paper a scientific review and it has been open to criticism for quite a while.

    Peer Review is not Scientific Review. Published suggestions and claims are common, and usually wrong, inconsequential, or impractical. Or all three.

  63. This proposition (without the reference to UHI effects — pertaining only to emissions) was the subject of a hilarious piece in the Winnipeg Free Press some time ago. My reply, at the top of the comments was mainly a link to some very well-formed rebuttals of the idea, my favourite being to member of an industrial company in whose economic interest it would have been to promote the roof-painting business, who points out that in a cool climate like Winnipeg’s, the proposition is nonsense, and would likely lead to greater emissions, not less. He said that this must be considered on a city-by-city basis as there are a number of factors to consider and the result is not at all clear. Any bets that this computer model neglects to take a majority of the relevant factors into account?

    In hot climates, cooling the city makes sense, but in cool climates, killing the UHI effect will simply increase the winter heating bill for everyone, and increase consumption of energy resources. UHI is not always a bad thing. One-size-fits-all solutions are sure to be the wrong solution some of the time.

    In any case if you just paint roofs and parking lots white around all Stevenson Screens in the world, we would see within a couple of years a sudden, pronounced, statistically significant cooling of the globe. But it would be as meaningless as the current data set that indicates warming, and for the essentially the same reasons.

  64. In the late 19th century the only rust preventative paint available was red lead, in South Africa this was widely used and the heat absorbtion made an alternative essential. The paint didn’t change, the Boers found the solution. It was a double roof.
    The house was given a roof as normal but a foot or so above that roof another roof was built. The eaves were sealed off to prevent the ingress of wild-life but wire-protected apertures were left to allow the air through. At the apex of the roof stood a louvered and roofed tower. When the air between the roofs heated it rose, and escaped via the vent on the top of the building. Cool air was drawn in from the verandah which surrounds all of the houses of that era.
    Result? The house stayed cool.
    White paint? Wrong choice.

  65. Hey! I’ve got it! Use a fleet of crop dusters to paint the entire city white! That’ll save lots of time. Dang, time to write to AlGore!

  66. “I studied this sort of thing about 50 years ago. You need a coating that is white in summer and black in winter. Any ideas?”

    Sounds like the perfect “shovel ready” green job program. During the spring, people dressed in white painters uniforms will be painting your roof white, then in fall people in black painters uniforms will be painting your roof black. Just hope they don’t run afoul of the “Green Police”.

  67. kwik (15:13:53) : the gray-scale based on lattitude

    I will suggest the cosine function. Send my consulting fee to . . .

  68. I would like to thank the SUN for doing a great job for me over the past 3 years.

    “Over longer periods of decades to centuries, solar activity waxes and wanes with a complex rhythm that researchers are still sorting out. The most famous “beat” is the 11-year sunspot cycle, described in many texts as a regular, clockwork process. In fact, it seems to have a mind of its own.

    “It’s not even 11 years,” says Guhathakurtha. “The cycle ranges in length from 9 to 12 years. Some cycles are intense, with many sunspots and solar flares; others are mild, with relatively little solar activity. In the 17th century, during a period called the ‘Maunder Minimum,’ the cycle appeared to stop altogether for about 70 years and no one knows why.”

    Solar Dynamics Observatory Set For Feb 9 Launch
    http://www.redorbit.com/news/space/1819249/solar_dynamics_observatory_set_for_feb_9_launch/

    There is no need to go so far back in time, however, to find an example of the cycle’s unpredictability. Right now the sun is climbing out of a century-class solar minimum that almost no one anticipated.”

  69. NOAA only wants to patch a faulty system by diverting to roof colour. On one hand they deny the UHI but say that cities have an impact on global warming. Sure it is hotter during day time but it’s only a heat capacitor that delays the discharge. It only delays the heat release but does not contribute to it. Also, as we said last week, the UHI is insignificant compared tot the rest of the land, water and snow/ice covered area.

    What? the city folks feel it’s too hot during night time? That’s what happens when you live in a chicken house, stacked on each other.

  70. I have a (nearly) white tin roof. I also have a weather station mounted 2 metres above the roof. I have another temperature monitoring point under the roof at the side of the house, which is next to a brick wall and above concrete.

    The one on top of the roof routinely measures 1-2 degrees cooler than the one in the shade. True story.

    I know somoene with a black tile roof. Their house is unbearably hot in summer.

  71. Why put a temperature measuring station in direct sunlight? No one who works outdoors, such as farmers, construction workers, you name it, would ask for a temperature reading in direct sunlight. In fact, they would consider you insane for giving a temperature reading from direct sunlight. Yes, I know the thermometer is in that little box. But that little box will heat up like the dickens. Well, that’s what you get when you leave temperature measurement to eggheads.

    The World needs an entirely new regime of temperature measurement created from scratch.

  72. John Luft (13:36:43) :

    …….What is obvious is that there is far too much money going to research and these guys are just looking for ways to spend it.

    This could not be more true. I’ve been listening to a radio ad for the last year, which plays several times each day. I was out very late one eve, and heard it at 2 am, admonishing citizens to plan for disasters. It is a government service announcement…. playing in the wee hours of the morning….. stimulating the economy….. because we’ve printed a trillion bucks and can’t think of enough ways to blow that much cash.

  73. I read Monktons justafiably sarcastic destruction of Chu, I notice an error (please correct me if I am wrong), in working out the surface area his maths assumed it to be flat (oh the irony), I do not know what conversion factor to apply in making a flat surface into the area swept by the suns rays but I would think that we can start by halving it as half is in the dark, then as we are discussing a sphere only the equator gets 100% one pole will get 0% so we can divide again, perhaps by 2/3 this time so we have to divide 0.2 F by half and by 2/3 my abacus gives me about 0.07F The really frightening thing is this was one of the saner ideas.

  74. John F. Hultquist (15:36:08) :

    Charles Barnard (13:32:48) : collect rainwater to store in tanks

    Thief! That sort of anti-social eco-corrupting behavior can get you thrown in the dungeon in some of our states in the USA. Washington, Colorado, and Utah are examples. There may be others.
    —————
    Reply:
    No cause for alarm; he’s just sequestering H2O, which is undoubtedly a much more effective GHG than CO2. He should get a medal, except for the fact that 70% of the earth’s surface is contributing that nasty H2O into the atmosphere. That rather overwhelms his efforts at being “green”.

    So drink more H2O, particularly that laced with CO2. But don’t you dare belch or pee.

  75. Why does UCAR get UHI mixed up with climate change? Assessment of climate change would have the UHI of city sites eliminated. They seem to think that UHI causes climate change – it does when it is left in the data and not properly adjusted DOWNWARD.

  76. oMan (14:47:14) :

    Agree that this is being done in a silly way by UCAR. Also second the questions about using solar panel arrays to intercept the light. Developing that point (and the changeable color idea, above), has any of these people ever used a tent fly? It would be interesting to try a white fly that is mounted over a black roof; the fly is used for hot months, then taken down in colder ones so the roof can soak up the energy. If you oriented the fly, you might even get some useful convection effects? Admittedly this is finicky, labor-intensive (although we might see some good innovation with self-furling sails etc.) and a fly might blow out or be baked to shreds in a few years. Still, I’m curious.

    And Cristo would have a ball with the aesthetic.

    The U. S. Navy has been doing this for decades (probably measured in fractional centuries). In the tropics, ships that are moored in port for extended periods, put up white canvas awnings to keep the tropical sun off the decks and bulk heads. With out the sun shade the metal superstructure gets so hot it will burn you during the heat of the day. They take the awnings down when they go to sea and there is air motion to cool things off.

    Radical concept — shade, and a reflective shade at that — just like the pull down window shades my grandmother used 50 years ago to keep the house cool during the summer. White washed buildings are also common in the Mediterranean, I wonder how the ancients did their computer model studies to come up with that idea to keep the buildings cool?

    These guys need to get out in the real world more, read a bit of history, and go find a sidewalk cafe and drink a beer and marvel at how cool it is under the collapsible umbrellas.

    The U.S. Navy also uses roof construction with double roofs in the tropics as described above in South Africa.

    Larry

  77. I live in an area where snow usually remains on the majority of rooftops all winter long. Interestingly, I still see UHI every day I go into town. Of course, it may be a bit less … or not.

  78. Sounds like a complete reversal of the paper they just wrote saying the UHI didn’t exist – this study says 5 -7* – I guess that means your right

  79. I have a dark brown Metal roof in NE Oregon-normally snowy. It doesn’t help much but the place is an oven without A/c-maybe there will be a Fed Grant…
    I am being cynical BTW..

  80. “Ed Reid (13:46:33) :

    It is refreshing to learn the UHI still exists; and, that its magnitude is still significant. Who knew!”

    Heresy! Phil Jones and some other guy proved UHI is minimal a decade ago using data they can’t find anymore (the very best sort of data I might add) . So the science is settled, OK…No more deviations. White roofs can make no difference to the settled science of there being no such thing as UHI.

    So there.

  81. Here’s a consideration.

    White things generally don’t absorb much energy, but neither do they radiate as much. Black absorbs a lot, and radiates a lot.

    A black roof in a northern climate will give you a warmer attic when the sun shines, but will cool more quickly when the sun is low, clouded over, or down at night, and up north you have less sun than the other conditions. So net, you are losing more than you gain. That makes white roofs preferable up north, too.

    Here in Houston, they’re pushing what they call radiant barriers for energy savings. Basically, they just paint the underside of the roof with aluminum paint, which doesn’t radiate as much heat down to the ceiling joists. In winter it reflects heat back down. White roofs would work here, too, but mildew would turn them black in a couple years.

  82. It brings in mind a question is the NCAR receiving a funding from the white paint producers or it does this so important research just due to mere incapacity of the supervisors to recognize this falsifies their no-UHI preaching.

  83. The Nobel Prizes (and the money) that they gave Obama, Pachman and Gore need to go to the folks who invent white tar and asphalt.

    If we put mirrors on everything would that help too?

  84. I thought the “official position” of the Eco-Chondriacs is that the UHI didn’t exist?

    (Or, at the very least, that it’s inconsequential.)

  85. A white roof would take care of the great horned owl problem I have. They sit on the roof of my house waiting for the bats to fly outa the attic. Which means I have white owl poop on my roof. My roof is black.

    On the up side, owl pellets are worth money! Specially the big ones. So I guess my spotted roof is worth it. Besides, the weath…I mean…climate cleans off my roof every rainy season.

  86. Andrew:
    A different version

    (1) Make up menacing climate stories running into thousands of pages
    (2) Go around saying – the science is settled
    (3) Get caught by bloggers
    (4) Admit sheepishly that errors were made
    (5) Ask for more grants to uncover the real science.
    (6) Smile

  87. I find it offensive that ordinary people hold down sometimes arduous, dangerous or boring jobs so that they pay taxes so that the likes of Keith Oleson can hold down cushy jobs (in air conditioned offices with nice government guaranteed pensions at the end of their careers) doing fatuous research that would be better contracted out to a local high school science class.

  88. I see you are all having fun with this proposal. So here is my contribution. The real purpose for this research is to justify hiring an army of people for the “green jobs corps” to paint roofs. Originally they probably considered using first sided mirrors on the roofs for high reflectivity but the computer simulation showed that the efficiency of creating IR was higher because emissivity of silver is higher than titanium oxide. Cost was not an issue. Also I heard there is rumor that the carbon traders are planning to sell coal dust to coat the snow in Washington so it will melt faster. But first they need a grant to prove that this idea will work!

  89. Oh, thank God they have a “newly developed computer model”!!!!!

    Gets back to the first question I posed 4-5 years ago when AGW hype grabbed us by the throat: HOW DO ‘THEY’ MEASURE THE EARTH’S TEMPERATURE?

    Next question, HOW DO ‘THEY’ ISOLATE CAUSE(S) OF CLIMATE CHANGE?

    Neither question answered!!! It’s hard to believe that every article still starts with the false assumption that CO2 OR SOMETHING is causing climate change, which omnipotent MAN must do something about.

    I’ve enjoyed SO much research published here and elsewhere in my search to understand. My conclusions: 1 – those who research the natural sciences should continue their pursuits to discover answers to endless questions about the natural world, and 2 – the AGW NONSENSE must stop.

  90. There are two separate issues here.

    First, the ‘Paint everything white’ recommendation does nothing for the property owner’s energy bill. You are just donating the paint to have a ‘nano’ effect on your community and an ‘atto’ effect on ‘the EARTH’.

    Second, regardless of the roof color, the insulation amount drives the reduction of heat transfer. Dark or light color has negligible effect in any warm or cold climate region.

  91. Wouldn’t it be much cheaper just to take thermometers from the roofs and site them properly?

    Temperatures down (about 1-3 degrees Celsius) – AGW problem solved.

  92. I have written in a previous article that whilst I don’t buy the co2 hypothesis man is undoubtedly having a localised effect on the climate. This was most notably in the form of UHI.

    This effect was noticed as far back as Ancient Rome and caused citizens to petition Emperor Nero to ‘make streets narrow and buildings high’ to help mitigate it. Pliny noted that Beech trees no longer grew in the city due to the additional heat. Rome had around one and a half million inhabitants and stretched for some 70 miles end to end.

    So UHI can be a problem in certain areas, but also arguably a boon in others. For example, in many Northern European latitudes, cities are overall a degree or two warmer due to UHI which helps plants to keep growing and generally makes the local environment more comfortable in winter.

    However, in more consistently hot countries the additional warmth is likely to be detrimental overall. The beneficial effects of painting buildings white in such environments was recognised centuries ago and can be seen in many towns and cities in such countries as Spain and Greece.

    So where UHI is a problem painting buildings white seems a reasonable solution to a local problem. Where UHI is a benefit it would be pointless.

    Tonyb

  93. This has been known for about 50 years that I know of…

    Results 1 – 10 of about 78,000 for silver roof coating

    and that was one of the SMALLER hits on google. Folks have been developing silver roof coatings for decades to keep buildings cool. Drive through any industrial park and look at all the silver roofs…

    Talk about trying to solve a solved problem…

  94. ” Oak Ridge National Laboratory wrote a computer program that calculates energy savings under different scenarios. In northern cities like Chicago, the dark roof surfaces actually save money because of the heat gain during winter ”

    Arnold:

    I hope this national lab roof color research opinion/conclusion reaches DOE Chief Dr. Steve Chu, it is embarrassing to hear roof white rational again from his mouth again in the public.

    And I totally understand now why he bought up AGW propaganda so faithfully, think of this as an experimental physicist with Nobel Prize Crown, he should have the most critical oppinion to any numerical modeling without experimental proof, however, as a director of LBNL, how could he say NO to one of his own department’s climate modeling work and not to fight research fund for them, it is just a matter of conflict of interest

  95. These are the mines, titanium and lime,
    That extracted the pigments
    To make the paint
    That went on the house that Jack built.
    These are the factories, emitting the fumes,
    That processed the pigments
    To make the paint
    That went on the house that Jack built.
    Here’s the albido the white roof creates
    To offset the warming
    From factories and mines
    To make the paint
    That went on the house that Jack built…..

  96. Can I have a nice new computer and some funding to research my theory that painting igloos black could save the Inuits some some heating costs and cut down on CO2 at the same time?

  97. I’d paint my roof white if it would save me a noticeable amount on my air conditioning costs. No government mandate necessary.

  98. That man Chu is a real genius.

    Who would have guessed that a little dab of white paint, could stop global warming in its tracks.

    Way back in 1977, I had a flat roof home, that was nice black tar paper; and being flat as well, it leaked like a sieve.

    So we added a partial second storey to the house, and then converted the remaining flat roof areas to a slight angle to get rid of the standing water, and get rid of the leaks.

    Just to be ornery, we also had the roof gooped white, and then spread a bunch of small white crushed rock, to break up water run-off, and increase the total surface area a bit, while making it white instead of black. The foam insulation under the tar paper, also helped, and the heating bills just vanished almost.

    I never imagined in 1977, that I was doing something of Nobel Prize Physics merit; I thought it was just common sense.

  99. Anybody want to hazard a guess as to why Shell Oil, is proudly announcing that they now have all three grades of “Nitrogen Enhanced” gasoline.

    Now I can sort of understand you can get some extra OOoomph from gasoline, by adding a shot of Nitro-Benzene; but I always thought that (a) Benzene rings are carcinogenic; and persona non-grata in Gasoline, and also that (b) Nitrogen in gasoline, would add to the burning of the nitrogen in the air, to make NOx; so how do they get away with this Nitrogen enhanced Gasoline ?

  100. “UCAR had to resort to modeling to prove something that can be measured empirically.”

    Yes, by painting every roof in a city white, they could have empirically measured the effect of painting every roof of a city white. To try and figure out the effect of something you CAN’T measure empirically, you need to do some kind of mathematical calculation. A… let’s see… a “model,” perhaps.

    I don’t think you do a great deal for your credibility by misreading an article and going haw-haw-haw.

  101. Common sense says that the heat bounced off the white roof bounces into the air inlets of nearby air conditioners, causing them to work harder and produce more GHG from more electricity. Or, it heats up the streets, so all it really does is redistribute the heat. OK if it’s redistributed to where you need it, not ok if it’s a heat pollution nuisance.

    There are so many variables in this model that it should be given to trainee GCM modellers learning tweaking, before they get the adult licence.

    If I may, on a related subject, can anyone tell me if the ground temperature lowers when clouds cover the sun? I know this is so in the tropics where I have mostly lived; but I have never measured near polar areas.

  102. Since 1989 our small Southern California company has “whitened” nearly 2,000,000 square feet of otherwise “dark” roofs. We participated in the regional Heat Island Studies and apparently, no matter how much fun is found in all of these comments (and one poem) – the building owners and building occupants DO benefit from and ARE PLEASED with their decision to graduate to a WHITE ROOF.

    White Roofs (we in the business of this call them COOL ROOFS) are, in fact, measurably COOLER – thus the process is known as “Cool Roof” or “Cool Roof Products.” IMHO, the major growth in White roof is very much analogous to voting in a political election where oftentimes voters vote with their Pocket Books.

    The cooler roof surface temperatures make for a longer-lasting roof. This is very important if it is YOU who has to write the check for a new roof every 7-9 years and by going White you can put off a $50,000 roof for a whole 20 years!

    If the extended Roof Life was news to the readers here, surely everyone instinct-fully KNOWS (common sense) that the cooler roof surface temperatures make for a cooler interior which requires less electricity to cool the interior. Come on! How many of us with a simple 5-ton home air conditioner weigh the cost of running the AC for all of July or August? We KNOW our electricity bill might go from $180 to $400 per month. How much more is the cost to a business with 30 5-ton AC units on their business? The pain of writing THAT check is no different…

    The interior temperatures of the Cool Roof properties we have transformed is absolutely measurably LOWER during our hot Southern California summers. Saving energy – saving MONEY makes the business owner / property owner a happy person! :0)

    In many of the simple concrete tilt-up industrial buildings where employees are working in a non-cooled, open door environment: manufacturer, warehouse, etc., we hear HOW MUCH COOLER the buildings’ interior is as soon as a non-white roof becomes a bright, white, reflective Cool Roof. We have 100’s of pictures of these common and typical industrial/commercial buildings on our residential website – just because so many people want to see them. (This is not a sales plug for us – we are not listing our commercial website here.) We are fans of reflective roofs: obviously…

    As most of the comments I have read suggest. White Roofs are just plain ‘ol common-sense. Much of the increase in White Roofs is a force unto itself. So called Greenies and Eco-Extremists aside, the growth of WHITE ROOFS is UP. I can speak to the fact that those building owners who don’t lose any sleep over “ECO” or “GREEN” are totally on-board the white roof movement because of finances. Even the most extreme, cut-and-dry capitalist wants a clean environment and healthy planet for their kids and grandkids – so the GREEN-factor that parallels graduating to white roofs is but rich, creamy icing on the cake for them. Which is good news for everyone.

    The GREEN that is moving the Installed Base of White Roofs into 30% of all new low-slope roofing is the GREEN left in the property owners’ wallet: roof life, roof replacement cost, energy cost of cooling.

    Thanks for your informative site Mr. Watt.

  103. Heat Painting roofs white would probably help cool NOAA weather stations that are positioned on rooftops, like this one on the roof of the Santa Ana fire station in southern California.

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