Aerial thermal scans over Perth – 16 years after this technology was used in the USA to measure urban heat island (UHI) effects

Chris Gilham has posted an item from the West Australian newspaper reporting the results of aerial thermal scans over Perth by a commercial firm Scantherma.
Of course this imagery can be used to prove the existence of the urban heat island (UHI) which magically never finds its way into IPCC temperature trends.
It is good to see this airborne technology used in Australia but airborne and satellite imagery has been detecting the UHI for decades. Here are several examples.

Summer land surface temperature of cities in the Northeast (USA) were an average of 7 °C to 9 °C (13°F to 16 °F) warmer than surrounding rural areas over a three year period, the new research shows.
Hong Kong study says – Air temperature typically reaches 37°C on the hottest summer days, cooling to 29°C in urban, and 24°C in rural areas at night.
Springtime land surface temperatures in eastern North American cities were on average 2.3°C (4.1°F) warmer than surrounding rural areas
also – Significant effects were seen up to 10 kilometers (6 miles) from city lines. In other words, the impact of urban climates on ecosystems extended out 2.4 times the size of a city itself.
A spot check of day temperatures around the Mall (Huntsville Alabama) shows that in the middle of the parking lot temperatures reach about 48.8 °C . However, a “tree island”, a small planter containing a couple of trees in the parking lot is only 31.6 °C. So, even a small area of tree coverage surrounded by a very hot parking lot reduced temperatures by a significant 17.2 °C !!
Canadian cities examples
Old site Wisconsin University
Old site of mine showing examples of satellite imagery
Atlanta (Hotlanta) and Florida satellite imagery showing Miami UHI

14 thoughts on “Aerial thermal scans over Perth – 16 years after this technology was used in the USA to measure urban heat island (UHI) effects”

  1. I am sure that you appreciate the point Warwick, but it is the CHANGE in the UHI effect over time that impacts the temperature trends. Showing that UHI effects happen is not enough. Any of us with a thermometer in our car reading outside temperatures can observe UHI any time we traverse a city.
    Change in UHI (lets call it Delta UHI to make it clear) over time results (usually but not always) from population growth, and the changes to the local environment that causes. The challenge is finding records of UHI effects going back in time.
    The reason I raise this obvious point is that so often discussions on UHI confuse the existence of a UHI effect with the Delta UHI over time which is what we really should be concerned about.
    Editor notes: Of course I am well aware from 20 years of temperature research that it is Delta T that is the vital thing. But I am happy to see the UHI talked about, mentioned in the MSM, pictured, thermal imaged, discussed over Chardonnay or Starbucks, whatever. We must remember there has never been a satellite image of Australian UHI published yet – not that I have seen.

  2. discussions on UHI confuse the existence of a UHI effect with the Delta UHI over time which is what we really should be concerned about.

    Why should we be concerned about the delta, Mondo? The UHI exists, that is a fact, as urban areas grow, the UHI area grows with it. Even so, it is still localized. Drive out of the city, and the temperature drops.
    And Warwick, you know the reason this information never finds its way into the IPCC temperature trends is because it isn’t about temperature, it is about sowing fear in order to gain power and money, and nothing else. It is the means to an end and always has been. And unfortunately, the alarmists seem to be winning.
    Editor note: This thermal imaging of Perth just reminds us that when the BoM regularly yak on about some “heat wave record” for Perth – they never mention the 100+ year expansion of the UHI geophysical feature.

  3. Mondo, yes, it is the CHANGE over TIME that creates a TREND.

    Would you like to explain to us how you know when this MEASURED warming started and in what quantities so you can ADJUST the trend to take into account this artificial BIAS in the observations?!?!?!?!

    Didn’t think so. Yet you wish us to swallow you TREND that does NOT take into account this KNOWN perturbation. Your official records are useless. The models are continue to be proven useless. Yet you continue to try and force radical CHANGE that will destroy the world’s economy and make most people paupers and killing an unknown amount.

    The Heartland use of Mass Murderers to get their point across was quite appropriate apparently.

  4. UHI increases may be observed as steps in a temperature record. Such steps are over a short period; perhaps a year or two; coinciding with construction and initial use of the change in surroundings of the measuring station.

    It appears that step-change in minimum temperatures is more pronounced than maxima. This phenomenon may be useful in detecting a change in physical environment from the temperature record; inviting one to investigate what may have changed in the surroundings. (My suspicions were thus aroused when seeing the temperature reord of a nearby station. WUWT coincidentally features an article on the effect of change in land use.)

    One must rule out changes to the physical environment before a change in temperature can be attributed to “climate change”.

  5. Drive out of the city, and the temperature drops.

    Thats what you would expect if its a heat generation or heat storage phenomena, but studies show that UHI extends well beyond the urban area itself, into nearby forests and similar, in particular downwind.

    Which indicates there is more to UHI.

    This is an interesting UHI study, uncontaminated by CAGWism.

    hokulea.soest.hawaii.edu/ocn435/classes/papers-class12/Taha-10.pdf

  6. 5: Philip Bradley Says: “Thats what you would expect if its a heat generation or heat storage phenomena, but studies show that UHI extends well beyond the urban area itself, into nearby forests and similar, in particular downwind.”

    Well, it is mainly a heat storage issue from the sun heating up the urban mass. Any man-made heat generation is tiny in comparison. And what is different from my statement, Drive out of the city, and the temperature drops, and your UHI extends well beyond the urban area itself? Both are inexact statements open to interpretation as to how far out of the city you have to drive and what the distance of “well beyond” is. Either way, the effect is still local and temporary over distance.

    Thanks for the link. I will try and read it later.

  7. Kuhnkat: You say “Would you like to explain to us how you know when this MEASURED warming started and in what quantities so you can ADJUST the trend to take into account this artificial BIAS in the observations?!?!?!?!”

    I think that you must have misunderstood my point. If we look at the “measured” temperature record (before unexplained adjustments) we need to recognise that many of the temperature stations are affected by UHI effects that exaggerate the warming. My point is that if UHI effects have not changed over time, then there will be no impact on the temperature record. If they have changed over time, for example by local population growing over time, then they will impact the temperature record, exaggerating it. I agree that we actually know very little about how UHI has changed over time. Thus, we know that UHI effects are exaggerating the observed warming, but we don’t know by how much.

    There are studies on the UHI effect, but I think that it is accepted by most sceptics that they don’t really address the issue.

    And I agree with Warwick that more information about the UHI effect is valuable. And should be examined and addressed.

  8. Mondo,

    I DO understand what you are saying. You need to explain the mechanism where these cities impossibly jumped from background temp to their current temp with no period of increase. THAT is what a step change is and the only way UHI won’t affect the TREND.

    You apparently haven’t thought through UHI. It is due to the change in materials and to a much smaller extent waste heat. If you build a block of buildings in a short period of time with assorted streets etc. there would be a step change. If you are continuing to build buildings, streets, sidewalks, parking lots… then you will not have sharp step changes except possibly with station moves or the changes close to the station. The overall change can be rather smooth for continuous growth. Of course, this is not neat and there may be multiple step changes due to local development and station moves and even due to plateaus in development and then another growth burst.

    One of the reasons I SPECULATE for the current plateau in temps is that many urban areas have maxed out their possible UHI based on materials and local circulation. This is partly due to economic attenuation, partly due to conscious restrictions on development, and partly due to physical limitations on how much heat can be captured and retained in the area.
    Editors note: Remember too that Delta T is most significant in very small urban areas. Exactly where it is most difficult to detect in data – exactly where data itself can be more gappy compared to a metro station.

  9. The take away from the study above is that cities generally have a higher albedo than surrounding areas (a problem for the surface heat retention hypothesis), and lack of vegetation and evapotranspiration appears to be more important in UHI than surface heat retention.

    Cities are also generally cloudier than surrounding areas with less solar insolation.

    All in all, UHI is due to a number of factors that vary by latitude, climate, season and between the developing and developed world.

    I’ll note that here in Perth, we see evidence of the Oasis Effect (cooler urban areas from increased evapotranspiration) when the Perth official station was moved from next to an irrigated park to an unirrigated field minimum temperatures rose 1.5C.

    Everyone irrigates their garden here.

  10. The heat generated in the city by waste heat does not make a significant contribution to UHI. Heat retention by paving and roofs will influence the minimum night time temperatures. The cause of elevated daytime temperatures and thus stored heat that needs to be dissipated at night is the lack of evapotranspiration. In rural areas and in suburban areas where sufficient green space is provided, a large amount of solar energy is used to evaporate water and not to raise the temperature.

  11. Strategies for minimising UHI have been discussed in the past, with ideas such as painting our roofs and paved surfaces white, and planting trees, etc.

    And quite amazingly, those who claim we must spend half a trillion dollars to reduce our emmissions of CO2 by a few percent and achieve no result, also forget to mention that we could spend a fraction of that amount to reduce UHI almost completely and actually make a large measureable difference.

    Funny that 😉
    Editors not; Good points John M – I have wondered for years too in view of the fact that most of the global population lives within the geophysical feature we can call the UHI – why have we not got university depts that study the thing. Bring all the science strands together.

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