The Alligator Model

Guest Post by Willis Eschenbach

I wrote my first computer program in 1963. It was an implementation of the Sieve of Erastosthenes, used to find prime numbers. I haven’t stopped programming since then. So I am intimately acquainted with the innards of computers, computer programs, and computer models, both iterative and otherwise.

And those who read my writing know that I don’t have much use for the suite of IPCC computer climate models as a way to predict the future evolution of the global climate. I think they are Tinkertoy™ exercises in parameter tuning.

So it may come as a surprise that there is a model out there that I wouldn’t say I trusted, that would be far too strong. But I would say that it certainly bears watching, because it’s the best of the models. It bears scant similarity to any of the IPCC models. In its current incarnation, it has the lovely name of GATOR-GCMOM.

It came up recently in a Discover magazine article entitled “White Roofs May Actually Add to Global Warming”. Go figure, huh? Figure 1 shows what painting roofs white was supposed to do for the climate.

Figure 1. How it was supposed to work … but didn’t. Ah, well. So much for the White Roof Project.

When I read the Discover story, I wasn’t surprised to find that the model that produced such a counterintuitive result was the same GATOR-GCMOM, whose development I’ve been following and speaking favorably of for over a decade. It’s the work of a brilliant man named Mark Jacobson at Stanford University. It started small, as a local or regional model to trace the paths of pollutants around point sources. In its current form it includes literally dozens and dozens of chemical, atmospheric, and oceanic processes which are not represented in any other climate model on the planet. It uses a variety of ingenious ways to do things to reduce computational overhead. A full list of the differences from IPCC models and a discussion of the development of the GATOR model is here (PDF).

So why does the GATOR-GCMOM model say that painting the roofs white will heat the planet?

The Discover article says:

The model found that more white roofs means less surface heat in cities (which is obvious enough to anyone who’s sat in a car with a black interior in the sun). Lower local temperature means less water evaporates and rises up to eventually form clouds, says lead author and Stanford University researcher Mark Jacobson. The decrease in clouds allows more sunlight to reach the Earth’s surface, leading to higher temperatures overall.

So, clouds once again affect the climate in an unexpected way. I’m shocked. The article also states:

The model also predicts that much of the light reflected by rooftops will eventually be absorbed by dark carbon soot and particulates that are especially prevalent in the air above urban areas. This could limit local cooling and cause warming elsewhere as the particles drift away.

This shows an unexpected (but reasonable) interaction between two factors, reflected sunlight and black carbon particles in the air.

Why would I think that Jacobson’s model might be showing something near reality in this question, when I am generally scornful of the IPCC models? Several reasons:

1. The time frame of the analysis is short, he’s not futzing around with 100 year fantasy forecasts.

2. Both outcomes, once examined, make sense. Changes in clouds, and in atmospheric heating from sunlight hitting black carbon, certainly would affect the outcome, the physics is well established.

3. The GATOR model started small, modeling local conditions, many years ago and built gradually outwards from there. From the start, it was frequently compared to reality and tested and refined. It wasn’t conceived of as a global model like many climate models. So it was continually being tested on how accurately it could represent the temporal evolution a host of local conditions around cities and bays, studying pollution plumes and their changes over time, comparing them to observations … a host of real-world testing unlike anything that any of the IPCC models have undergone. Then, over about twenty years, it has been slowly expanded to be a global model.

4. I may be wrong, but I cannot find any indication of tunable parameters anywhere. Seems like there must be some somewhere, but for the most part it’s truly physics and chemistry based, unlike IPCC models.

5. It uses a nesting grid scheme which allows for a variety of grid-size resolutions as needed. This lets some areas be intensively sampled (say around a city) while a larger area of the ocean might need far fewer samples.

6. It handles chemistry at a very detailed level, involving hundreds of chemical compounds in both the ocean and the atmosphere. Other climate models don’t even touch chemistry except perhaps in the simplest ways.

7. The result was counterintuitive, but still demonstrable. A model that only shows us what we already know is not that useful. This one showed us something we didn’t know.

Anyhow, for me the takeaway message is CLIMATE ISN’T LINEAR. The IPCC paradigm is, change the forcing and the temperature has to change proportionally.

But in this case, not only is the temperature response not proportional. It’s not even in the right direction. Kinda deals the whole “temperature change equals forcing change times climate sensitivity” idea a body blow …

So that’s all the reasons why I find this result quite plausible. It’s the best model on the planet, and it is uniquely qualified to look at this particular question. If Jacobson were to start using the model for hundred year runs looking for trends, that would be a big question mark for me, I don’t think any model can do that.

But for this kind of analysis? It does what the best of models can do—it points at things in front of our eyes which we might not have noticed. Doesn’t prove anything, the output of a computer model is never evidence … but it certainly teaches us something, which is much more valuable. It teaches us that in a complex system like the climate, a simple, totally obvious cause and effect relationship may not work out anything like that. As in this case, where something that obviously, logically, and unquestionably will cool the earth … may just end up warming it.

Anyhow, that’s the latest news from the land of Settled Science, where all temperatures are unshakably tied to forcings …

Regards to everyone,

w.

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64 thoughts on “The Alligator Model

  1. Willis,
    If you keep coming to sensible conclusions and ideas such as this, you will become a target of displeasure to those on the AGW side, keep your a@se covered.

  2. Heh. Interfere with the H2O cycles at your peril! Evaporation and recondensation are the big dogs; they bite hard.

  3. Lower local temperature means less water evaporates and rises up to eventually form clouds
    This may be true in some locations, but urban evaporation (from rainfall) is low anyway (storm drains).
    But I am sure its not true in other locations such as mediterranean climates where a cloud free sky is the norm during the summer.
    Then there is the Urban Irrigation Effect, which significantly raises near ground humidity during the summer in places like Perth. Where most people run sprinklers several times a week to water their gardens.
    This near ground humidity rarely results in clouds. It seems you need quite a deep column of humid air to create convection clouds.
    While the model sounds interesting, I’m somewhat sceptical of the quoted conclusion above.

  4. “But in this case, not only is the temperature response not proportional. It’s not even in the right direction.”
    Balderdash! I have actual experimental results refuting this so-called model (and just in time for the next climate conference!). I’m still writing the press release for my not-yet-peer-reviewed not-yet-written paper, so I can’t reveal the details yet, but I will say that my experimental method involves two glass cookie jars…please keep this info confidential.

  5. Hmm, if we wanted to increase global temperatures I wouldn’t suggest painting everything white.
    But I wouldn’t suggest pumping greenhouse gases either.
    I would suggest putting soot in glaciers and ice in general.
    And I would suggest way of absorbing more solar energy- since we don’t want to absorb energy on roofs reflecting the energy or painting white would be fine- not the issue.
    Probably simplest way would put salt lakes on the Sahara desert such bodies of water would absorb a lot of energy and evaporation carry the energy elsewhere. And to be useful mine the salt [let a few lakes dry up and rotate to different lakes] and also plant crops in area also.

  6. I wonder if he explicitly models CO2. Might an increase in atmospheric CO2 concentration speed warming and evaporation in the am and then increase cloud cover and/or precipitation in the pm, for a net reduction in earth surface temperature?

  7. The major effect of white roofs is to reduce demand for air-conditioning and so reducing power demand. The direct effect on climate will be small.
    The feedbacks you get so excited about here are the sort you would dismiss as third order effects if they were in the other direction.
    If there was enough aerosol in the atmosphere to absorb “much” of reflected sunlight, there would be enough to absorb “much” of the incoming sunlight. Certainly this effect is real, and slightly reduces the efficiency of white roofs, but probably by no more than a little dirt on the roof reducing the albedo.
    The cloud argument is equally trivial. Cities only take up a small proportion of the earth’s surface – any change in albedo in cities can only have a minimal on the overall formation of clouds.
    Climate change is a long term phenomena – how are you going to predict how the climate will have changed in a hundred years without running the models for a hundred years. If you want to argue that that cannot be done, then you have to accept that uncertainly about the effects on climate are large. Doubt may be the product of the so-called sceptics, but uncertainly is not their friend.

  8. So what we wind up with after painting all the roofs is a broken thermostat™.
    Or maybe not. Because the reduction of clouds which inconveniently caused more warming, will eventually evaporate more water and create those clouds and cooling rain later, thereby kicking the thermostat on again. My mind is spinning.
    All in all, I would say that your famous thermostat hypothesis is perfectly safe and very hard to dispute. I’m not sure that any amount of tinkering can really break it’s functionality.
    But about those white roofs. It is not like the bulk of humanity and their humble abodes lie at low latitudes in deserts. The idea was hogwash all along because so many people do not want or need sunlight reflecting roofs. They might want them for 8 hours a day for 3 months of the year. Perhaps in the future they’ll have computerized auto-polarizing White in summer, Black in Winter. But that ratio in a year would still be like a minimum of 75% of the time black anyway. Does anyone even go outside anymore?
    Yep, pie-in-the-sky insanity. It is a lot like light bulbs. There is a definite place for both incandescents and the alternatives (or white and black roofs). Yet someone always has the chutzpah to attempt to make a blanket decision for *everyone*. The correct answer in both situations is to use the color roof (and type of light bulb) that bests suits your specific circumstance.
    And those politicians and scientists that attempt such single solution mandates must be scorned, fired and more.

  9. The idea of painting houses white also fails for anyone not in the tropics….
    If painting the roof while lowers the temperature of the house (ignoring for a moment what it does to the area), it will be a bit cooler in the summer, but also cooler in the winter…thus for many people who dont have a/c (ie most people outside of North America…), but do have heating (pretty much everyone), the net result will be more heating needed. Thus pumping more heat out in the winter, and requiring more of those evil CO2 producing power plants.
    For me, in the UK, we need the heating on from October to April. All the time.
    Whereas the number of days that A/C would be usful is maybe 2 weeks in the year

  10. Do cities produce more convective cloud than nearby areas? If observations show this then the model may have some relevance. Otherwise it is just more of the same modelling masturbation.

  11. richardjamestelford says: October 21, 2011 at 1:30 am re white paint reduces load on air conditioning.
    Must be 2 years ago I disagreed with the thesis that painting the town white would make it cooler. One main reason is that hot air reflected from a white roof top is the very air that gets sucked into the feed of the adjacent air conditioner, requiring a higher power input. Another factor is that the heat reflected by the white can still find its way between buildings and heat their sides instead of their tops.
    The main way a town gets cooler if painted with white roofs is by relocation of energy by some (unstated) mechanism away from the town for dissipation in to the air of less dense populations.
    As I’ve written n times, you can’t analyse effects like this with intuition and a simple static mind game. Gather all of the relevant numbers and crunch them in an interactive dynamic program for so long as they stay valid.

  12. I live in a rural area, and have noticed that over the winter, there do tend to be clouds over the two nearby “cities”, such as they are, when the sky is otherwise clear. Never thought about it much though, except that I thought they were more proof of UHI as these clouds often show convection when there is very little convection, if any, anywhere else in the winter months.
    Funny too that in the summer months, you may see large flocks of buzzards circling lazily on “thermals” to gain altitude over airports and mall parking lots. I wonder where these are in the models?

  13. “For me, in the UK we need the heating on from October to April. ”
    As general rule maybe have white roof if average temperature is 15 C.
    So southern Spain or similar warm climate. Or say, if get average solar energy more than 5 kW/h per square meter.
    So places like UK, Germany, most of France, Seattle, or New York it doesn’t make much sense for thermal reasons.

  14. …much of the light reflected by rooftops will eventually be absorbed by dark carbon soot and particulates that are especially prevalent in the air above urban areas.

    I’m dubious of that. When I look at a daytime sat image I can easily see the difference between lighter colored city areas and darker forest areas such as my back yard where the afternoon temperature can be 10F lower than Boston in the summer. On Santorini all the building are white and you can easily see them from space so ‘much’ does not appear to be absorbed.

  15. I’m not sure that I agree that painting a roof white will cause the world to warm, but there are several folks here who have argued that they need a black roof in the winter for warmth. You guys are forgetting that things radiate away energy at the same rate that they absorb energy. We paint wood stoves black for a reason. A black roof that is hotter than its surroundings will radiate energy away, just as a black roof will absorb energy from direct sunlight. In the winter, there is less sunlight than there is darkness, so a black roof will tend to cool the home more than a white roof will.
    On the lines of “white roofs, less clouds” I’d like to add that the burning of fossil fuels has water as one of the emissions. All of the cars, all of the people breathing, all of the bath, shower, dishwashing, car washing, irrigation, etc. that goes on in a city, as well as the extra soot that darkens the streets, walls, and air around a city will make the effects of the roofs smaller. I believe there is enough hot water vapor in inhabited areas that we will still have plenty of clouds.
    The advantage of a lighter colored roof, that occurs to me, is lower energy bills. There’s no reason for us to decide that better, more efficient use of energy is a bad thing, regardless of it’s use to combat CO2 caused Global Warming. For the record, I don’t think CO2 is warming the planet. In fact, I think we’re just rebounding from the LIA, right before our plunge into the next glaciation period, but what do I know?

  16. This could limit local cooling and cause warming elsewhere as the particles drift away.
    … but this doesn’t change the aggregate total global energy; it merely reduces a local “hot spot.”

  17. Good thing the California Air Resources board decided that mandating reflective paints in cars was not cost effective (“banning” black cars was the common theme when it was proposed). Too bad they don’t apply the same cost/benefit analysis to their cap and trade.

  18. Willis, I’m a bit jealous. You probably got to use old Eratosthenes’ old computer after he was done with it. I started in 1966 myself.
    Your reasons for liking some features of this model smell good to me as well.

  19. I dropped my subscription to Discover a few years ago after they featured an article by Laurie David. Prior to that, I would have characterized the content of the magazine as “Lukewarm,” meaning while they supported the belief that AGW was real, they weren’t alarmist or strident about it.

  20. Willis,
    Does the GATOR model calculate an estimate of climate sensitivity (ie. degrees K warming per doubling of CO2 concentrations)?
    If so, I’d be curious to know how their estimate compares to others?

  21. Dave:

    In the winter, there is less sunlight than there is darkness, so a black roof will tend to cool the home more than a white roof will.

    Take two identical houses of identical roof temperatures in the dark but with one black and one white then yes I agree that the black one would cool the house quicker. But that is an over-simplified initial condition that won’t occur on a sunny winter day. The black roof collects heat during the day and the white one collects none. Ignoring the fact that the warmer black roof is also conducting heat to the air in my attic thus reducing delta T across the insulation below it, when the sun goes down my black roof is warmer than your white roof. The black one is radiating both ways part of which is warming me and my house below for part of the day and then into the night. The white roof stored no heat so it just stays bone cold day and night. At some point in the middle of the night the white roof would eventually be retaining more heat but I think testing is the only way to determine which color roof actually offers a net heat advantage over 24 hours.
    (Now you have me thinking about snow and ice damning, thanks a bunch!)

    • Mike M says:
      October 21, 2011 at 7:45 am
      Dave:
      In the winter, there is less sunlight than there is darkness, so a black roof will tend to cool the home more than a white roof will.
      Take two identical houses of identical roof temperatures in the dark but with one black and one white then yes I agree that the black one would cool the house quicker. But that is an over-simplified initial condition that won’t occur on a sunny winter day. The black roof collects heat during the day and the white one collects none. Ignoring the fact that the warmer black roof is also conducting heat to the air in my attic thus reducing delta T across the insulation below it, when the sun goes down my black roof is warmer than your white roof.
      =======================
      Mike, I agree that during the hot daylight hours, the black roof will be warmer than the white roof. It will also cool off much faster. At the point where the roof cools past the temperature of the insulated interior, the heat transfer begins to the outside.
      If the temp outside is cooler than inside, the temperature flow will be outward, regardless of the color of the roof, right? Heat only flows in one direction; from hot to cold. So, even if the white roof does not warm as much as the black roof during the day, a warm attic will attempt to warm the cold air outside it, hampered only by the insolation and the speed of the heat transfer properties of the surface of the material. As I remember it, the heat transfer is governed by a) surface area, b) color (for radiation) and c) thermal conductivity for convection. The air touching the roof will cool it by convection, and the difference between the temperature of the roof and the sky will cool it by radiation. Surface area would remain the same between the roofs.
      Correct me if I’ve got these factors wrong. So, unless the sun warms your roof to hotter than the inside temperatures, deltaT is always going to be outward. I think most of the temperature is going to be transfered via convection. If the air is cooler than the interior, the warmer roof tiles will warm the air faster than it will the interior of the roof. Also, with longer cooling periods than warming periods, the roof will lose heat to convection AND radiation for something like 16 hours a day, and lose to convection but gain through radiation only half of that time. Depending on the strength of the solar radiation in your part of the world, the daylight hours will have a weaker or stronger effect on the temperature of the tiles and the heat transfer.
      I still maintain that a black roof will lose more energy during cold weather than a white roof.

  22. The model found that more white roofs means less surface heat in cities (which is obvious enough to anyone who’s sat in a car with a black interior in the sun). Lower local temperature means less water evaporates and rises up to eventually form clouds, says lead author and Stanford University researcher Mark Jacobson. The decrease in clouds allows more sunlight to reach the Earth’s surface, leading to higher temperatures overall.
    This seems really counter-intuitive. Looked at the other way around, the paved surfaces in cities that are currently absorbing sunlight should be raising the evaporation rates and creating more clouds. This would lead to a net COOLING according to this logic. So the “Urban Heat Island” effect would be a net COOLING of the rest of the world as much as it is a warming of the cities.

  23. 4. I may be wrong, but I cannot find any indication of tunable parameters anywhere. Seems like there must be some somewhere, but for the most part it’s truly physics and chemistry based, unlike IPCC models.
    The is the number one key factor in making a model that might actually produce meaningful results.
    Any model that has a “tunable parameter” is subject to the “experimenter expectancy effect” or “clever Hans effect” When the model doesn’t fit what the experimenter expects, they change the parameters so that the model fits their expectations.
    This has the effect of introducing errors into the model, because not all inputs to the model are 100% accurate. So, in effect by tuning the parameters, you are making it impossible to isolate input errors from model errors. Over time this allows errors to build up in the model, so that its value for accurate prediction is reduced. In effect the model ends up predicting exactly what the experimenter expects it to predict, not what the model’s internal physics says it should predict.
    Whether climate science recognizes the problem or not, parametrized models are machine learning programs. Their design is such that they are intended to learn and deliver more accurate results over time. Back-casting is a machine learning technique. You are training the machine using past experience in the hope that this will improve its future performance. As is done when training animals, humans and students. In the case of back-casting the effect can be even more subtle, as the computer typically adjusts its own parameters (weights) to improve the fit. Any errors in the inputs thus train the model to make errors in the outputs.
    As such, computer models suffer from much the same problem that occur in animal learning studies. Unless climate models are designed using double blind or similar techniques, they are unlikely to deliver meaningful results.
    Here is what Wikipedia has to say:
    ” Recognition of this striking phenomenon has had a large effect on experimental design and methodology for all experiments whatsoever involving sentient subjects (including humans).”
    http://en.wikipedia.org/wiki/Clever_Hans#The_Clever_Hans_effect
    http://en.wikipedia.org/wiki/Observer-expectancy_effect

  24. RE: richardjamestelford October 21, 2011 at 1:30 am
    I have to agree with you. I don’t know about the sky over Stanford, but most of the US cities I’ve visited are not so sooty that absorption of reflected sunlight could ever be a significant factor.
    Likewise, the difference in evaportation would have to hit just the right sweet spot to make a difference. It could be the case that there is enough evaporation to form clouds even if the roofs were white, so the white roofs would have no warming effect in this case. And if having dark roofs didn’t form a cloud then the additional water vapor as well as the additional IR emissions would increase local greenhouse warming, along with the heat directly transferred into the air from contact with the hotter roof.
    I’m a big fan of Willis’ writing, but think his trust in the GATOR-GCMOM model is misplaced, especially in light of this result.

  25. “an implementation of the Sieve of Erastosthenes”
    That’s always the first or one of the first programming assignments I give when teaching programming. A great way to see if their code is tight – or not.

  26. richardjamestelford says:
    October 21, 2011 at 1:30 am

    The major effect of white roofs is to reduce demand for air-conditioning and so reducing power demand. The direct effect on climate will be small.
    The feedbacks you get so excited about here are the sort you would dismiss as third order effects if they were in the other direction.

    Easy for you to say now. Where were you when the “White Roof Project” was getting all of the press? How come you didn’t let Secretary Chu know?
    If you can break out a statement of yours from before this study saying the same thing, that white roofs would not cool the earth but would warm it, that would be impressive.
    Right now, it just sounds like my kid saying “I knew that already, Dad” …
    w.

  27. Harold Ambler says:
    October 21, 2011 at 3:20 am

    Mark, with whom I went to high school, is 100-percent on the AGW bandwagon and — not infrequently — holding the reins. See his work on “CO2 domes” — http://pubs.acs.org/doi/full/10.1021/es903018m — in which he specifically indicates that CO2 is lethal (with some wiggle words, just in case).

    I know that … but damn, the boy can build a model. I don’t think it (or any) model can solve the basic questions about CO2 as people are always trying to do, using 100 year runs.
    I do think the model can be useful, though, for studies like this one.
    w.

  28. Russ R. says:
    October 21, 2011 at 7:23 am

    Willis,
    Does the GATOR model calculate an estimate of climate sensitivity (ie. degrees K warming per doubling of CO2 concentrations)?
    If so, I’d be curious to know how their estimate compares to others?

    I’ve never heard of it doing so, if it does.
    w.

  29. Great work, Willis. Your description of the model strikes just the right balance between its use as an Analytic Tool to reveal things that we do not yet know, the net warming effect of white roofs, and its incorporation of an unusually complete Description of the Natural Processes underlying the phenomena investigated. To be clear, the natural processes include the chemistry not found in other models. All of this is not yet science, as you recognize. The science comes in creating and testing physical hypotheses which provide a more complete and detailed description of the natural processes that make up climate. Limited parameters means limited rejiggering and limited fudging.
    Thanks for getting out the message about this model and its author.

  30. This whole thread is scientific navel gazing on a par with the worst of realcimate (and that for me is the benchmark).
    The science being discussed here is totally irrelevant to the problems that face the human race (the planet is fine by the way).
    The issue is about climate; is it changing, how is it changing and why is it changing? Any and all computer models including the gator variant are totally and utterly useless. Any and all currently understood science is totally and utterly useless.
    If you dont understand everything about how and why the climate of this planet changes then you dont know anything at all in terms of predicting the future.
    Scientists need to show a little humility and accept that.
    If you dont understand everything then controlling the climate is a pipe dream. It is quite possible that in a thousand years when (highly unlikely) we do understand absolutely everything, we will still not be able to control our climate.
    History is telling us a great deal about how climate changed in the past, highly intelligent and well educated humans should concentrate on making sure we can survive (as a society and as a species) the events of the past. That is the best we can do.
    The fact that some scientists and apparently all politicians are crippling the world economies, depriving their citizens of hard earned freedoms, comfort and in some cases lives in order to prevent one possible contributor to climate change is the most disgusting insanity I have ever witnessed.

  31. TomB says:
    October 21, 2011 at 8:12 am

    “an implementation of the Sieve of Erastosthenes”

    That’s always the first or one of the first programming assignments I give when teaching programming. A great way to see if their code is tight – or not.

    In 1963, nobody’s code was tight, not by modern standards. Plus we were using ALCOM (IIRC), an ugly inefficient language to start with.
    These days I program in R, and I can’t recommend it enough. Steve McIntyre was the one who got me into using it, and it has been much more than worth it.
    w.

  32. Quick hint for someone wanting to become the next Steve Jobs or Bill Gates. Develop a material which can be changed from black to white and back using a trickle of electricity (something like liquid crystals, but not necessarily the same). Then hook it up to a computer and computer program (say using panels one meter square as the unit). Feed the program the layout of the house, the Solar insolation, and the weather forecast. Let it determine which panels should be white and which black at a given time. Should reduce heating and air-conditioning costs much more than the cost to run the system. Caveats and details left as an exercise for the entrepreneur.

  33. This sounds like an unstable feedback effect. White roofs reflect sunlight from the surface causing the average surface temperature to be cooler so less clouds form allowing more sunlight to reach the surface and thus making the average surface temperature warmer than it would have been if the sunlight had not been reflected from the roofs in the first place.
    Perhaps there is just a simple negative feedback effect that results in about the same overall surface temperature no matter what color the roofs are.

  34. Spector [October 21, 2011 at 9:39 am] says:
    “Perhaps there is just a simple negative feedback effect that results in about the same overall surface temperature no matter what color the roofs are.”

    That’s what I was trying to say above. You are describing the Thermostat Hypothesis™ by Willis, in action.

    “So what we wind up with after painting all the roofs is a broken thermostat™.
    Or maybe not. Because the reduction of clouds which inconveniently caused more warming, will eventually evaporate more water and create those clouds and cooling rain later, thereby kicking the thermostat on again. My mind is spinning.
    All in all, I would say that your famous thermostat hypothesis is perfectly safe and very hard to dispute. I’m not sure that any amount of tinkering can really break it’s functionality.”

    It sounds intuitively correct to me, although I think Willis was describing the tropics in particular. It may be time for him to update this theory and expand it to elsewhere.

  35. Dave – heat flow is proportional to the DIFFERENCE in temperature between the warm and cold sides T1 & T2. If the black roof raises the temperature of the outside of the insulation by 2 degrees, (T1 is inside the house, T2 is inside the attic with the insulation being on the floor of the attic) – that’s a 2/R reduction of heat flow.

  36. With regard to cooling at night, I note that (having worked on selective surfaces in the 70s when this was a big flap) emissivity in the infrared can be can be quite different than in the visible. Thus dark-skinned people (cleverly) appear white in UV light and are less susceptible to skin damage near the equator. So to get a net solar gain in winter you need a paint black in visible light and white in the infrared. In summer you need the opposite to reduce AC load. Both are hard to get as the on and off work on selective surfaces continuing for some 40 years shows.

  37. But … but … but …
    Gavin has spent decades … decades … decades … refining his models …
    Surely anything else is inferior

  38. So what happens when we move away from coal fired electrical generation and to mainly electric or H2 cars. Will we get rid of enough atmospheric black carbon to reverse this effect?

  39. richardjamestelford: The feedbacks you get so excited about here are the sort you would dismiss as third order effects if they were in the other direction.
    That is correct. My question to Willis is, do you still believe that third-order effects are too small to care about?
    One way or another, doubling CO2 in the next 70 years will produce a third-order effect, but it probably makes a great difference to us whether the net effect is to raise or lower global mean surface temperature from what it is now, or have no effect at all.

  40. Two comments:
    First – I really wonder whether much vaunted Nobel Prize winner Sec.Steven Chu is going to be fired or admonished by Obama for peddling the “paint roofs white” concept to combat “global warming”. Solyndra then this added to much else – I don’t think we have ever had a worse science adviser for a President.
    Second – I looked twice at the PDF describing GATOR and could find no references to incoming solar radiation or other than ‘variation in earth-solar distance’ … Since it is completely clear to me that at least half (and likely more than 80%) of temperature change on Earth is due to variation in Sol, GATOR&MOM is incapable of being used to explain temperature changes here.
    If anyone here has noticed indication somewhere that GATOR actually does include solar variation/ irradiance variation/ comic ray, etc., in some sneaky less defined way, I would appreciate them flagging me as to the page of the PDF that is described.
    AFPhys

  41. blockquote>Gary Pearse says:
    So lets put water pools on our roofs and cool the planet down and maybe even get rain in Texas.
    I have a better way.
    First, you need nuclear power, and plenty of it.
    Yes, nuclear power, safe and cheap.
    Yes, that same nuclear power that the press is constantly saying is sooo dangerous.
    Yes, that same nuclear power that, despite being sooo dangerous, and despite being available in great quantities in Japan, where they had a huge earthquake and a tsunami, has still killed or even injured exactly zero people.
    Just keep telling yourself, number of people killed in Japan by radiation, still zero…
    You can ignore the recent newspaper article that spoke of radiation “hot spots” found in some Japanese city, since it admitted that the radiation was so small that it was harmless to anyone, which means that the spots were not “hot”, and which thus showed that the entire article was nothing more than a bald faced lie. I guess “cold spots” just doesn’t have the same punch to it.
    Now that you have all that safe, cheap power (also useful for air conditioners…), you can build a desalination plant or two or a dozen. Now that massive sucking sound you hear from the cities drinking up all the water the farmers need goes away. Now not only do you not need to ship water to the cities, which the farmers can use, you can even pipe the water to the farmers directly. And now all that water means the farmer farm, and all that electricity means the factories produce, and the local economy booms.
    To sum up:
    You live in Texas.
    Texas is a desert.
    Droughts are frequent in Texas.
    Texas is next to an ocean.
    Nuclear power and desalination plants exist.
    Nuclear power is cheap.
    Japan has shown that nuclear power, even from old power plants, is safe even under the most extreme conditions.
    Put the two together and your water problems go away.
    Conclusion, you need to take you local politicians, and your local mainstream press, and run them out of town on a rail. Make sure you bring plenty of tar and feathers.
    Uh, make them white feathers.

  42. About white roofs –
    Good in the summer to keep attic temperatures down.
    Good in the winter, too, as opposed to black roofs. Black is a good absorber of sunlight in the winter, but it is also a good radiator of heat for the great majority of the winter day when the sun isn’t up. White, on the other hand, impedes the radiative transfer of heat, summer and winter, definitely a color for all seasons.
    Painting roofs white would provide lots of green jobs, tho they would likely be taken by the illegals who are already doing most of the re-roofing work in America. It would likely also void the manufacturer’s warranty on your shingles.

  43. Septic Matthew says:
    October 21, 2011 at 12:11 pm

    richardjamestelford: The feedbacks you get so excited about here are the sort you would dismiss as third order effects if they were in the other direction.

    That is correct. My question to Willis is, do you still believe that third-order effects are too small to care about?
    One way or another, doubling CO2 in the next 70 years will produce a third-order effect, but it probably makes a great difference to us whether the net effect is to raise or lower global mean surface temperature from what it is now, or have no effect at all.

    The effects in the white roof case are enough to swing the effect of the white roofs from a strong net cooling (see what was expected in Figure 1) to a weak net warming. That is a very large swing.
    Richard and Matthew, how on earth you can mistake that for a third order effect is beyond me. It’s a large enough effect to put the White Roof Project entirely out of business … good luck convincing them it’s only a third order effect …
    Nobody, and I mean nobody, predicted this outcome or anything like it … and now you want to pooh-pooh it by calling it a third order effect?
    That spells A-G-E-N-D-A to me, it let’s me know you’ve got one.
    w.

  44. AFPhys says:
    October 21, 2011 at 1:17 pm (Edit)

    … Second – I looked twice at the PDF describing GATOR and could find no references to incoming solar radiation or other than ‘variation in earth-solar distance’ … Since it is completely clear to me that at least half (and likely more than 80%) of temperature change on Earth is due to variation in Sol, GATOR&MOM is incapable of being used to explain temperature changes here.
    If anyone here has noticed indication somewhere that GATOR actually does include solar variation/ irradiance variation/ comic ray, etc., in some sneaky less defined way, I would appreciate them flagging me as to the page of the PDF that is described.
    AFPhys

    I doubt it. GATOR, as far as I know, is used for short-time analysis (some years or a decade) of problems like the one above. Since the future unraveling of the sun’s output is not known, it’s not possible to include it (other than in the most general way).
    So for the problems GATOR gets used for, I don’t think solar variations are meaningful, and for predictions of the future (that Mark Jacobson seems to steer away from) it can’t be predicted.
    w.

  45. Geof Sherrington,
    the air does not absorb much visible solar. The reflected energy from the white roof would NOT significantly warm the air. The decrease in IR from the roofs would more than balance the increase in visible radiation and cause a decrease in the air temp. Higher up where you have aerosols and clouds to absorb more of the reflected visible it may balance or be warmer. I’ll tentatively agree with the model this time!!

  46. The whole debate seems pointless. Guess what? many commercial roofs are already employ a reflective coating. Heat accelerates decay of the roofing material and reduces its service lifetime, increasing maintenance costs. Commercial roofs need to be re-coated every 15-20 years in any case. Residential roofs in the US typically employ shingles rated between 10 and 25 years; I suspect 15 years is probably about average (the 25 year shingles cost significantly more). We don’t need a Dept. of Energy initiative to paint roofs — they will all be redone sometime in the next 20 years anyway. And the people paying the bills will make decisions on material and color which are locally optimal (as best they can determine). If people believe lighter colored roofs will lower energy costs, they will use them (local homeowner associations permiting).
    Given time, roof color will converge toward the optimal balance of cost, esthetics, and function. Let’s see: if we assume that will take 20 years at 3mm sea level rise per year, that means the oceans will rise another 6 cm before we get this roof radiation thing under control. Which is, ummm, approximately exactly the same as it would rise if we spent however many Billion$ to paint all the roofs white this year.
    I don’t think in this matter we should pay any attention to what any model shows.

  47. ferd berple says: October 21, 2011 at 7:47 am
    The is the number one key factor in making a model that might actually produce meaningful results. …..

    fb – your explanation to Willis’ post was informative, thank you.
    And reitererated in another post above Stephen Brown @ 4.56pm provided a link to
    http://www.bishop-hill.net/blog/2011/10/20/best-paper-out.html#comments
    In climatology the standard progression is:
    1) Policy changes
    2) Publicity
    3) Scientific publication

    And possibly at a later date, if the computer is large enough, proof (though this step is optional)
    Oct 20, 2011 at 9:20 PM | ZT

    Perhaps ZT could have added to 1) establish regulatory and legislative change.
    dlb says: October 21, 2011 at 3:42 am
    Do cities produce more convective cloud than nearby areas?

    Given that the majority of cities are established on a coast (?) http://www.tyndall.ac.uk/cities-and-coasts-publications that is an interesting question I hope someone answers.
    Like Y2K, could it be like the lead (paint and then atmospheric) or asbestos debacles?
    For the home handy man (or woman) where the (25yr) warranty on roofing material has expired. Or not! http://www.heritage.nsw.gov.au/docs/maintenance4-1_corrugated.pdf and information on roof painting, including a reasonable overview of the variety of roofing material in NZ/Aus http://www.resene.co.nz/homeown/h2pyhome/Painting_Roofs.pdf
    Also publication ‘Walls and Roofs in South Africa’ (and 25 degrees in Africa) provide an overview of the town planning and architectural industry (and energy). http://www.mediainafrica.co.za/

  48. I notice that on high convective summer afternoons when we get the popcorn variety thunderstorms that they often spawn from whatever major roadways happen to be in a loosely parallel direction of low level wind, (also where you see some birds like hawks riding thermals right up to the base of rapidly forming clouds several thousands of feet up). But, just like a pot of water about to boil, even though the first bubble will generally start at the hottest spot, the whole pot is going to boil no matter where the first bubble formed.

  49. Of course we all know that painting the roofs is merely an academic discussion here, for two simple reasons:
    [1] :: Many roofs (speaking about asphalt tiles here, not clay, stone, wood) are NEITHER black nor white already. For the past 3 or 4 decades our roofs have always been what I would call gray with black speckling, which I see everywhere. So we kinda split the difference in this argument long ago. I have seen darker shades and lighter shades but the majority seems to be in between white and black already. So why did this nitwit Chu even bring this subject up?
    [2] :: Painting anything is a love-hate affair. This goes double for outdoor things. This goes quadruple (or probably octuple) for roofs and all items in direct sunshine, alternating between freezing and boiling, wet and dry. There is no place more extreme than a roof. Painting them is a losing proposition, there is no chance for success. But let’s say against all logic you do it anyway. Well the paint comes from somewhere, usually the lowest bidder. So a really great question is: how do Chinese paint particles running off into the groundwater factor into AGW eco-zealotry?

  50. Septic Matthew says:
    October 21, 2011 at 12:11 pm

    One way or another, doubling CO2 in the next 70 years will produce a third-order effect, but it probably makes a great difference to us whether the net effect is to raise or lower global mean surface temperature from what it is now, or have no effect at all.

    A Swedish scientist observed that the tragedy of climate science was that meteorology began during the coldest decades of the last 10,000 years. That implicit “normal” has biased everything.
    Global warming? I should bleedin’ hope so, and thank all the gods for it. It’s been a huge boon and relief from the horrors of the LIA. Long may it continue!
    [Changed “3” to “1”, which is what I think you intended. If not I’ll change it back. ~dbs, mod.]

  51. philip Bradley says:
    October 21, 2011 at 12:47 am

    Lower local temperature means less water evaporates and rises up to eventually form clouds
    This may be true in some locations, but urban evaporation (from rainfall) is low anyway (storm drains).
    But I am sure its not true in other locations such as mediterranean climates where a cloud free sky is the norm during the summer.
    Then there is the Urban Irrigation Effect, which significantly raises near ground humidity during the summer in places like Perth. Where most people run sprinklers several times a week to water their gardens.
    This near ground humidity rarely results in clouds. It seems you need quite a deep column of humid air to create convection clouds.
    While the model sounds interesting, I’m somewhat sceptical of the quoted conclusion above.

    It takes a pretty shallow thinker to accept this and other glib assumptions of Jacobson’s GATOR model. “Somewhat sceptical skeptical” (fixed that for ya) is a somewhat reasonable position to take. Exceedingly skeptical would be the most reasonable.
    As with all other climate models these are hypotheses stated in computer lanugages rather than human language. The translation to computer language does nothing to improve or test the hypotheses. All it does is grease the wheels that produce hypothetical predictions. Like any other hypotheses these predictions must be tested in some fashion. So one might reasonably ask how it is that Jacobson’s model predictions are tested?
    And just as a side note for Willis, it is NOT well established that black carbon in the atmosphere causes heating. You’re conflating that with black carbon on the ground, particularly on snow or ice. In the atmosphere it is generally believed the greater effect is surface cooling because it blocks sunlight from reaching the surface. The notion that it would “move” urban heat to other areas because the particles would heat up from sunlight reflected off white rooftops then drift elsewhere is asinine. The heat capacity of soot particles is essentially zero.

  52. Dave Springer says:
    October 23, 2011 at 12:01 am

    … And just as a side note for Willis, it is NOT well established that black carbon in the atmosphere causes heating. You’re conflating that with black carbon on the ground, particularly on snow or ice. In the atmosphere it is generally believed the greater effect is surface cooling because it blocks sunlight from reaching the surface. The notion that it would “move” urban heat to other areas because the particles would heat up from sunlight reflected off white rooftops then drift elsewhere is asinine. The heat capacity of soot particles is essentially zero.

    Two things, Dave.
    First, the heat capacity of a typical soot particle is undoubtedly greater than that of a molecule of carbon dioxide simply because it weighs more … perhaps you’d care to comment on that in light of your claim that the heat capacity of soot is zero.
    Second, you haven’t thought the carbon question all the way through. Black carbon in the air is warming with respect to reflected sunlight, you are conflating that with incoming sunlight. It is different from the case with incoming sunlight because if the reflected sunlight misses the black carbon, it most likely goes on to space. If it hits the black carbon, it stays in the system, which inevitably must lead to warming.
    w.

  53. Brian H says:
    October 22, 2011 at 6:01 pm

    There’s been a massive real-world experiment in reflective roofs, in a high-sunlight locale. In Spain, much of one province, Almeria, has been given over to greenhouses — and the glass and plastic etc. reflect brilliantly. Result: a drop of 0.3°C in average temperature per decade.
    http://geographyfieldwork.com/images/Climate/AlmeriaGreenhouses.jpg

    The Almeira temperature record is here. Please point to the “drop of 0.3C in average temperature per decade”.
    I ask because there’s not enough data there to say anything at all about the Almeira temperature, much less identify a 0.3°C change. Where did you get that number from?
    w.

  54. The fundamental problem with all computer models is that computers can not represent numbers exactly and they can not preform even basic arithmetic functions like additions and subtraction completely accurately because of how numbers are represented. Most of the time these minuscule inaccuracies can be ignored, but when you keep iterating these functions over the datum 10’s or 100’s of thousands of times on thousands of data points, there is no such thing as minuscule inaccuracies.

  55. Willis;
    I’m just parroting the article:
    http://geographyfieldwork.com/AlmeriaClimateChange.htm

    Since the 1980s, Almería in southern Spain has developed the largest concentration of greenhouses in the world, covering 26,000 hectares. The greenhouses reflect so much sunlight back into the atmosphere that they are actually cooling the province, Spanish researchers have found. While temperatures in the rest of Spain have climbed at rates above the world average, meteorological observatories located in the so-called sea of plastic have shown them moving in the opposite direction, with a decline of 0.3 degrees per decade. T

    So actually the total impact is greater, 0.3 + ~0.7 increase elsewhere, or 1.0°C/decade:

    The result was that temperatures in the region have fallen by an average of 0.9 degrees since 1980, when greenhouses expansion began, while in Malaga, Granada and Murcia-San Javier the increase has varied between 1 and 3 degrees. Thus there has been a difference of more than two degrees. There have been no significant changes in rainfall.

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