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Whitewash and bias, Painting over the historical record


Chris Knight

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Posted
  • Location: Worthing West Sussex
  • Location: Worthing West Sussex

    Measurement of temperatures since the beginning of the 20th century have been extensively standardised, to reduce bias due to inadequately housed instrumentation and recording methods. The first consideration is the box that houses the instruments.

    1. The Stevenson Screen is a standard, so Stevenson Screens in the same location have remained unchanged in design over many years, right?

    Wrong, a Stevenson Screen is a general pattern for a ventilated wooden box, set at a standard height above the ground and protected from direct irradiation from the sun, in order to accurately measure the air temperature and humidity. A such it can house several other weather related instruments for ease of observation and recording from the same geographical location.

    Technologies change, even with regard to double louvred boxes. Different woods have different properties with regard to specific heat, response to humidity in regards to thermal and water absorbency and evaporation. At one time it was thought double layers of asbestos sheet would provide the best surface for the roof, with either a single slope or roof ridge. Later, asbestos containing materials were deemed hazardous and replaced with laminated wooden materials. Woods also age and rot and have to be replaced.

    In the original design, the wood was designed to be covered in whitewash, a porous lime containing coating that needed to be replaced annually or as required which also had the added benefit of preventing timber rotting, The lime hardens, with the addition of various natural additives to form a white calcium carbonate based coat which is essentially opaque to infrared radiation, absorbing it with the typical spectrum of calcite, and re-emitting longer wave radiation.

    As a porous coating, the timber beneath would become moist and dry out depending on the weather conditions, which must have led to some biassing of the temperatures within, as a damp structure in strong sunlight would reduce internal temperatures due to loss of heat through evaporation compared to actual exterior temperatures. In prolonged warm dry periods, internal conditions would become warmer than comparative damper periods where the actual temperature of the air was the same as measured inside. There would be corresponding biassing of relative humidity conditions. A ground frost, freezing the water in the roof of the structure may sufficiently cool the air inside to under-record the temperature as an air frost.

    Over time, the popularity of whitewash waned, in the general market, where white Lead pigmented oil based paints, Alkyd and other plastic containing alternatives were available at reasonable cost, with the benefit of their colour permanency, impermeability and durability. Later these were supeceded by Brilliant white paints, which replaced the toxic, grayish lead oxides with the whiter titanium oxides, and the improving durability of latex bases over oil and alkyd. Lately, there are some fluorescent additives to make the white look whiter, by absorbing UV wavelengths, and reradiating them at lower frequencies in the visible and infrared wavelengths. And the wood underneath stays dry, needs painting less often, and doesn't flake off, just gets dirty.

    Well they are white like the whitewash aren't they? Yes, in the visible spectrum, but apparently in the infrared, they are transparent. This means that the wood beneath heats up, and being dry and kept dry underneath an impermeable coat, continues to stay warm, radiating longer wavelength radiation in all directions, raising the temperature in the box.

    Over time, the boxes are overpainted, insulating further the underlying wood, and reducing the louvre aperture, increasing the potential for greater heat retention from direct radiation from the sun. This increases the potential for greater maxima of temperatures recorded at all times of the year. A heavy hoar frost on the surface of the roof may not lower the internal temperature sufficiently to record an air frost.

    So what would be the overview for say the same box in use for several decades, using Lime whitewash? It would underreport temperatures in damp weather and probably give fairly accurate temperatures during prolonged dry spells. As its coating deteriorated, it would start to overreport during sunny weather, as the exposed dry wood re-radiated daily heat.On re-whitewashing, it's response would return to a response similar to it's original installation.

    If it was repainted during a dry spell with a metal oxide oil based paint, the wood would heat up overreporting periods of high solar irradiation, but accurately reporting dull weather temperatures. As further episodes of repainting go on, the wood would stay warmer longer due to the insulating layer build-up of the paint. A brilliant white modern paint would also add energy from the UV spectrum to the system.

    Eventually someone notices that the louvres are getting a bit painted up and they order a new box from one of the many scientific instrument supply companies, nice new wood, brilliant white painted louvres, and they do a changeover, and do they run the old system alongside the new one? No, they trust the calibration of their old thermometer, and their perception of the accuracy of their past readings continues with their pride in their new white box.

    When someone from a brand new satellite system wants to calibrate their land temperature readings, they calibrate them to this old established surface station.

    And so it goes around the world at thousands of well established, reliable stations.

    Why do the troposphere temperatures diverge from the surface readings? Why do tree ring temperature series increasingly diverge from the surface readings?

    Could it be that the surface temperature data is actually wrong and has been ever since we started to statistically correct data that "just couldn't be correct" in the wrong direction in the achievement of our daily means etc.?

    Does this mean that man-made global warming could be man-made temperature data error?

    Probably because the surface readings could have been wrong from the start and that the current standards are not stringent enough.

    The belief in infallibility of well tested systems over time is very strong.

    The suggestibility of people is strong. We are used to central heating and better insulated buildings in winter and air conditioning and better insulated buildings in summer. A hot summer day seems to be a very hot day, coming from our air con car into our chilled supemarket. We are told that the temperatures are in the upper twenties - hot. The converse on a cold winter's day. Minus 1 - very cold, windchill minus fifteen, arctic. Outside the accepted range for the UK -definitely not.

    Our Climate is supposed to be changing because in the 2000s we get hotter summers, milder winters; or as it was in the sixties, colder winters, cooler summers - our stance has changed 180 degrees in direction over 40 years. Outside the range of variation for our climate - definitely not.

    This has been exemplified in our average temperature, wet summer of 2007 - perceived as being a cool awful summer (for some people it was awful, no doubt), but outside the realms of our climate - definitely not.

    Our climate is not changing in any direction different from the last 8,000 years, anywhere on earth, even at the poles, which have just experienced vastly different conditions than previously reported (with the caveat that only 30 years of comprehensive data and 100 years of sketchy data is actually recorded in the north and much less at the south). Outside the potential variation for the regions - definitely not.

    The Antarctic loses most of its ice and recovers more than ever recorded in a single season, the Arctic reaches record minimal ice ever, at the same time.

    Has it the capacity to recover and more in a single season?

    Time will tell, and none of the experts are predicting, as the loss was not predicted by them. Perhaps we are not yet the experts we believe we are?

    Or are our premises based on inadequate data and not as strongly based in fact as we would like to believe?

    Perhaps, since the observations are moving further away from the predictions, at a faster rate than expected, we should reexamine our data, rather than change our models to fit what we observe.

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    Posted
  • Location: Swallownest, Sheffield 83m ASL
  • Location: Swallownest, Sheffield 83m ASL

    Chris.. I looked into this last night after your post.

    I think you may have a very very valid point here. Possibly one that has very much been overlooked.. White is not just white. It comes in various flavours.

    I remember at the back end of the 70's when I was doing the Duke of Edinburgh's award scheme, that whitewash was recommended for a screen. I duly did that as whitewash was readily available to me, as we looked after the church hall greenhouses.

    Very interesting post mate.. :rolleyes:

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    Posted
  • Location: Nr Appleby in Westmorland
  • Location: Nr Appleby in Westmorland

    My understanding is a Stevenson Screen merely protects the thermometer from the sun whilst allowing airflow to circulate. Airflow isn't going to be changed by the type of coating the screen has on its topmost layer. Surely on all but the calmest days, the amount of airflow over the thermometer would massively overcome any difference the themal properties different coatings might have?

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    Posted
  • Location: Swallownest, Sheffield 83m ASL
  • Location: Swallownest, Sheffield 83m ASL
    My understanding is a Stevenson Screen merely protects the thermometer from the sun whilst allowing airflow to circulate. Airflow isn't going to be changed by the type of coating the screen has on its topmost layer. Surely on all but the calmest days, the amount of airflow over the thermometer would massively overcome any difference the themal properties different coatings might have?

    Increase the internal temperature and you'll get more air flowing through.. multi errors..

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    Posted
  • Location: Nr Appleby in Westmorland
  • Location: Nr Appleby in Westmorland

    No you won't! The airflow will depend on the wind speed. How can you increase the internal temperatures if the airflow through it is sufficient anyway? The air isn't hanging around long enough to get warmed.

    Am I missing something? I'm just applying simple logic I think.

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    Posted
  • Location: Worthing West Sussex
  • Location: Worthing West Sussex
    My understanding is a Stevenson Screen merely protects the thermometer from the sun whilst allowing airflow to circulate. Airflow isn't going to be changed by the type of coating the screen has on its topmost layer.

    But internal temperature may be affected by radiation within the enclosure and airflow depends on external airflow too, a still day is different from a windy day, hence the windchill factor. If the radiation on the enclosure causes the enclosure to radiate inside due to inadequate thermal protection, the internal temperature will be overreported. Conversely, an enclosure that is damp and evaporating will act like an unglazed pot wine cooler, keeping the inside cool, despite higher temperatures outside, underreporting the external temperature.

    Radiation affects the temperature reported by a thermometer, or else why do we screen them?

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    Posted
  • Location: Swallownest, Sheffield 83m ASL
  • Location: Swallownest, Sheffield 83m ASL

    What I'm thinking is that if this has been overlooked then someone needs to have their backsides kicked.. This is basic stuff.. :rolleyes:

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    Posted
  • Location: Worthing West Sussex
  • Location: Worthing West Sussex
    What I'm thinking is that if this has been overlooked then someone needs to have their backsides kicked.. This is basic stuff.. :rolleyes:

    I'd like to know what standards, BSI or otherwise the Metoffice requires for one of their accepted stations, and how the academics who have defined HADCRUT HADCET etc have carried out their QC on their raw data!

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    Posted
  • Location: Worthing West Sussex
  • Location: Worthing West Sussex
    Well QC is another question.. I don't think that data will be very forthcoming..

    Assuming the observations re. paint vs. whitewash that I made in the initial post, the timescale of the "hockeystick" global warming fits in quite nicely with the coating technology changes over the timescale, considering your earlier post, Pottyprof. Have any of the other professionals posting here got any anecdotal evidence I wonder, regarding their kit?

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    Posted
  • Location: Swallownest, Sheffield 83m ASL
  • Location: Swallownest, Sheffield 83m ASL
    Pottyprof. Have any of the other professionals posting here got any anecdotal evidence I wonder, regarding their kit?

    I'm sure more will come Chris..

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    Posted
  • Location: Steeton, W Yorks, 270m ASL
  • Location: Steeton, W Yorks, 270m ASL
    I'd like to know what standards, BSI or otherwise the Metoffice requires for one of their accepted stations, and how the academics who have defined HADCRUT HADCET etc have carried out their QC on their raw data!

    Let me explain how huge data sets are validated Chris - and the UKMO has HUGE data sets.

    Say I measure the temperature at two sites, A and B Over time I can see a pattern establish between the sites, such that one will tend to be warmer than another, let's say A is warmer. Suddenly, inexorably, the gap either grows or shrinks. Over three or four years I note that A, instead of averaging 1C above B suddenly becomes 1.5C warmer.

    Your logic had me chuckling by the way, I've seen some desperate arguments against warming, but this is by far one of the most ridiculous. Anyway, I digress.

    The UKMO do not simply take the data and do nothing with it. IN the same way that BP test the quality of their refined product rather than shipping it all to the pumps and hoping for the best, and Premier Foods produce test batches of Mr Kipling cakes - they don't just ship all the cakes out to supermarkets and hope there are no flaws - and the T&A press in Bradford check on copies of the Telegraph, or Independent, or whaterver else is running through the presses; so the UKMO test their data - they don't just produce the Hadley numbers and hope for the best.

    So, Mr Senior Forecaster spots the change in pattern, or equilibrium, between the data sets, and sets off to investigate what's going on. He will do a few things. Most obviously he will check the sites to see whether there has been a change in environment, but the other thing he will do is look for ther corroborating data, perhaps from other nearby sites. If there is no other data he will set up a temporary site nearby, using lab calibrated kit, to check for accuracy.

    For the utterly ridiculous scenario you have suggested to have any plausibility whatsoever absolutely every screen in the country would have to be degrading at the same rate, being painted with the same paint, and even then - as OON has pointed out - require a distant stretch of probability to be introducing an unseen skew.

    Presumably, by the way, the same paint is mysterisoulsy causing the number of frosts to reduce, and snow to become increasingly scarce.

    I will never cease to be staggered by the ability of some of the margins of N-W to believe that they have somehow identified potential forcing mechanisms that have eluded far greater, far more alert, and far better equipped minds than any of us on here can come close to.

    Please tell me you're just trolling Chris.

    ... A ground frost, freezing the water in the roof of the structure may sufficiently cool the air inside to under-record the temperature as an air frost.

    ...

    Does this mean that man-made global warming could be man-made temperature data error?

    ...

    Our Climate is supposed to be changing because in the 2000s we get hotter summers, milder winters; or as it was in the sixties, colder winters, cooler summers - our stance has changed 180 degrees in direction over 40 years. Outside the range of variation for our climate - definitely not.

    ...

    The Antarctic loses most of its ice and recovers more than ever recorded in a single season, the Arctic reaches record minimal ice ever, at the same time.

    ...

    I'm sorry, but there really is some total and utter tosh in there Chris, and before you get upset I'm being polite to you.

    'Ground frost' on the top of a Stevenson screen...isn't that part of the reason why the height is set at 4' or so.

    Did the Antarctic lose most of its ice this year. Have you bothered to check any of the data.

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    Posted
  • Location: Near Newton Abbot or east Dartmoor, Devon
  • Location: Near Newton Abbot or east Dartmoor, Devon

    I've got a Stevenson Screen.

    In the winter when the sun is low, or whenever it's cloudy, it really matter not a jot if it's white or super white - the box will measure ambient temperature. Now, in the summer in the Sun quality of paintwork might matter. But my Stevenson Screen is old and the woodwork partly rotten. That rotten wood gets wet and when warmed the water will evaporate - that will COOL the Stevenson Screen.

    Surely this is also a major problem, a false cooling of the record. No?

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    I must say this is a truly ridiculous argument. Stratos did a good job. Other signs of warming aren't explained by this:

    How do you explain satellite measurements showing warming?

    How do you explain sea temperatures warming?

    How do you explain the Arctic melting at huge rates?

    How do you explain the decrease in snow cover?

    How do you explain increased minima? No sun at night.

    Could go on...

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    Posted
  • Location: Near Newton Abbot or east Dartmoor, Devon
  • Location: Near Newton Abbot or east Dartmoor, Devon
    I must say this is a truly ridiculous argument. Stratos did a good job. Other signs of warming aren't explained by this:

    How do you explain satellite measurements showing warming?

    How do you explain sea temperatures warming?

    How do you explain the Arctic melting at huge rates?

    How do you explain the decrease in snow cover?

    How do you explain increased minima? No sun at night.

    Could go on...

    It's obvious, they're all caused by paint :rofl:

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    There's any easy way to find out if this is true or not. Have two thermometers side by side, one protected with a stevenson screen with whitewash and another with ordinary white paint. Measure their readings over a day, and if there is a difference you may have a point. If there isn't, then the theory doesn't stand up.

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    Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

    Thank you Stratos, for adding some science to the argument...

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    Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield

    All I can say that the kit needs to be maintained properly. So you'll need to keep it painted as that will reflect the heat and also prevent the wood rotting. Comments have been about the airflow. There will be airflow through the screen but this will also depend on the amount of breeze outside the screen somewhat. A still day and a screen that's not been painted which is standing in the full hot sun would more likely than not give a slightly higher reading.

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    Posted
  • Location: Near Newton Abbot or east Dartmoor, Devon
  • Location: Near Newton Abbot or east Dartmoor, Devon
    All I can say that the kit needs to be maintained properly. So you'll need to keep it painted as that will reflect the heat and also prevent the wood rotting. Comments have been about the airflow. There will be airflow through the screen but this will also depend on the amount of breeze outside the screen somewhat. A still day and a screen that's not been painted which is standing in the full hot sun would more likely than not give a slightly higher reading.

    Right, on about 10 days a year? Ok, say it's thirty days (far higher than it is imo, but lets run with it) - 10% of days. So there is a tiny error on 10% of the days. How big an error is that in total? TINY!

    And, might not the cooling effect I mentioned be as significant cancelling out the problem (if there is one) of poor quality paint?

    If AGW scepticism has to run with this paint 'critique' it's in big trouble.

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    Posted
  • Location: .
  • Location: .
    How do you explain satellite measurements showing warming?

    How do you explain sea temperatures warming?

    How do you explain the Arctic melting at huge rates?

    How do you explain the decrease in snow cover?

    Looks simplistically good doesn't it? And then you stop and think, 'hmmmm .... don't think they had satellites in the C16th'. Satellites have only been measuring global temperatures in a matter of years. Sea temperatures have not been properly and systematically measured over sufficient time. Arctic ice has indeed hit a minimum this year, but antarctic ice which accounts for 90% on the planet hit a maximum this summer (albeit with the same caveats over measurement). Snow cover is untested as a theory of proof of GW, and is as patchy science as the alleged snow cover.

    The reason many of us use the CET as a benchmark is because it is long lived, but it's therefore entirely valid to raise issues about the measurements.

    The more you look at the so-called solid science, the more valid questions are raised.

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    Posted
  • Location: Nr Appleby in Westmorland
  • Location: Nr Appleby in Westmorland

    Ok Richard, so do you consider the chances of readings creeping having anything to do, even remotely, with the covering used on Stevenson Screens?

    With specific reference to the airflow, I'd say there's less than 1% of the time when my anemometer isn't turning round, and if it's turning round, then air will be flowing through any Stevenson Screen being used for official records.

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    Looks simplistically good doesn't it? And then you stop and think, 'hmmmm .... don't think they had satellites in the C16th'. Satellites have only been measuring global temperatures in a matter of years. Sea temperatures have not been properly and systematically measured over sufficient time. Arctic ice has indeed hit a minimum this year, but antarctic ice which accounts for 90% on the planet hit a maximum this summer (albeit with the same caveats over measurement). Snow cover is untested as a theory of proof of GW, and is as patchy science as the alleged snow cover.

    The reason many of us use the CET as a benchmark is because it is long lived, but it's therefore entirely valid to raise issues about the measurements.

    The more you look at the so-called solid science, the more valid questions are raised.

    You are even questioning we are warming at all?

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    Posted
  • Location: Worthing West Sussex
  • Location: Worthing West Sussex
    All I can say that the kit needs to be maintained properly. So you'll need to keep it painted as that will reflect the heat and also prevent the wood rotting. Comments have been about the airflow. There will be airflow through the screen but this will also depend on the amount of breeze outside the screen somewhat. A still day and a screen that's not been painted which is standing in the full hot sun would more likely than not give a slightly higher reading.

    Except that modern paint is transparent to infrared, due to the composition of oxides of titanium, whitewash is more opaque due to its composition of calcium carbonate. Not all "white" in the visible spectrum is white in the infrared, some is effectively "black". Radiation is what thermometers respond to, and

    What we need is a new design standard for all "Stevenson Screens" included in the data gathering stations across the globe, that have been designed to insulate the interior from the effects of radiation on the outside of the cabinet, whilst allowing air flow and thus temperatures to be accurately monitored. These should be run side by side for at least a year or so with the traditional cabinets so that any station bias may be eliminated, and the past data examined, and corrected to correlate with the new standard.

    Then maybe we can examine the facts rationally.

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