Comparison Between Observational Data and Model Projections for Hot Days in Northern Australian Regions

Guest essay by Dr. B Basil Beamish

In a recent WUWT post I looked at the number of hot days (Tmax > 35 °C) projected by climate models for Cairns as published in a joint CSIRO and Bureau of Meteorology report (McInnes et al, 2015). Several replies to that post queried the reference base of the number of hot days used from the report and I thank those of you who took the time to raise that issue with me. As a result I revisited the original technical report (CSIRO and Bureau of Meteorology, 2015) and discovered that my assumption these values were based on a 30-year moving average climatology was incorrect. In fact the values for the different locations in Table 7.1.2 of the report on page 98 for scenario 2030 RCP4.5 are a 20-year average for the period 2020-2039 centred on 2030.

I have therefore amended my graph for Cairns and Figure 1 shows the 20-year centred averages from 1980 through to the end of 2015. The average for the period from 1996-2015 is centred on 2006. The warming trend projections required to reach the modelled outcomes for Cairns shown in Table 1 are drawn on the graph.


Figure 1. Trend in the number of hot days for Cairns showing trends required to achieve the model projections contained in the CSIRO/BOM report.

The larger set of hot day projections for Australian regions contained in the more comprehensive technical report (CSIRO and Bureau of Meteorology, 2015) provides an opportunity to take a look at a wider snapshot of hot days in Northern Australia. Projected hot day averages for Darwin and Broome are shown in Table 1. The corresponding trends in hot days for each of these locations from 1980 through to 2015 are shown in Figures 2 and 3 respectively.



Figure 2. Trend in the number of hot days for Darwin showing trends required to achieve the model projections contained in the CSIRO/BOM report.


Figure 3. Trend in the number of hot days for Broome showing trends required to achieve the model projections contained in the CSIRO/BOM report.

From the trend lines shown in each of the graphs for Cairns, Darwin and Broome it is possible to calculate the number of hot days required in successive five year periods to remain on trend. These values are contained in Table 2. For each five year period that the number of hot days falls below the average number required to reach the model projection value, the number required in subsequent years will increase.


This comparison between observational data and model projections provides us with an opportunity to track the progress of any climate change taking place in these Northern Australian regions. A copy of the spreadsheet for Broome is made available here for you to verify the analysis provided and it can also be used to add in data from successive years to track the validity of the model projections as the graph is automatically updated.

Again I would emphasise:

  • Any model projection needs to be validated against actual observations before any confidence can be placed in the model results.
  • Accountability of model projections should be mandatory and comparisons similar to this one should be performed on a five yearly basis, particularly if the models are continually adjusted.
  • As each five years of data becomes available it should become readily apparent whether the model projections are either validated or not.


CSIRO and Bureau of Meteorology, 2015. Climate Change in Australia Information for Australia’s Natural Resource Management Regions: Technical Report, CSIRO and Bureau of Meteorology, Australia, 216p.

McInnes, K et al, 2015. Wet Tropics Cluster Report, Climate Change in Australia Projections for Australia’s Natural Resource Management Regions: Cluster Reports, eds. Ekström, M et al, CSIRO and Bureau of Meteorology, Australia, 48p.

Data and Analysis Spreadsheet: broome-hot-days_wuwt (Excel .xlsx)


38 thoughts on “Comparison Between Observational Data and Model Projections for Hot Days in Northern Australian Regions

    • Robert try using the spreadsheet and see how it goes. For these particular sites both the ACORN-SAT data and the raw data are the same for the time period used in the analysis. It is what happens moving forward that counts. Any adjustments made to the data from this point will become very obvious.

      • Yea but the BM (Bureau of Meteorology) numbers have no credibility.

        With all due respect all you’re doing is performing accurate mathematical transformations (+, -, X, /, etc) on dirty data, and drawing some multi-colored graphs…which came from dirty data published by a bunch of government hacks, so it has no credibility or explanatory power.

        Depending on your point of view, that’s either a problem or a waste of time.

      • And people like you and me are forced to check, and will check their honesty since they have PROVEN incapable of being honest on their own. NASA should take heed much to my chagrin!

      • Dr. B I looked at your spreadsheet and found it interesting. If you change a couple of things in the formula that you are using in cells T41 – T64 you will get your intended output .
        You are using =IF(N51=””;#N/A,AVERAGE(N32:N51))) now
        change to =IF(N51=””;”#N/A”:AVERAGE(N32:N51))

    • The Bureau isn’t interested in showing any sort of cooling whatsoever. Dr. Beamish is drawing a line in the sand so we can hold their feet to the fire as time goes by.

      • You indeed correct. If we do not draw this line, in five years time the goal posts will be shifted with an updated model and everyone will lose track of what was projected previously.

      • Past data will be adjusted, excuses will be made, and the goalpost will still get moved. Models will be called new and improved.

  1. Someone please explain to me what CO2 has to do with record DAYTIME temperatures? Incoming radiation makes trapping outgoing radiation irrelevant. CO2 can’t warm anything, it can only slow cooling by trapping/ thermalization of existing energy. Daytime temps are due to incoming visible light, not outgoing IR.

    • CO2isLife September 8, 2016 at 3:26 pm

      Okay, its not the CO2 it self. Electromagnetic radiation, AKA sunlight ,TSI, is the culprit. Protons. Weird “particle” be yet not a particle. At rest it has no mass but in motion at “C” it does, thus it has energy and motion. CO2 as other GHGs interact with the proton’s motion. This interaction with GHGs is where the energy or heat comes from.

      someone will correct my poor explanation but the key fact is it is not the CO2 it self, but that there is slightly more of it for the protons to interact with; which keeps the protons active in the atmosphere slightly longer.

      And CO2isLife I agree with your handle it is life


      • Wait…wut? Protons are causing the warming now? I knew those hydrogen ions were up to something sneaky.

      • Try photons. CO2isLife, there are plenty of very simple explanations about this process on the internet. I guess you should have done a little more research before choosing your name.

      • tony mcleod September 8, 2016 at 6:17 pm
        When I was checking I found protons, I also have heard the term before in context. The Two “particles” seem similar both having no mass at rest.
        Thank you for pitching in.
        Not my area of expertise


      • “Bulldust September 8, 2016 at 5:41 pm

        Wait…wut? Protons are causing the warming now?”

        Protons are cars, didn’t you know?

  2. to do a real projection forward I need to have the data again going back to the beginning of the 20th century

    • Thanks Anthony. The more people who look at the data available for themselves the better. There are no black boxes here just basic maths and some graphing.

  3. So once again we see a model created by the people who believe in human-caused global warming (now called climate change, but still about human-caused global warming) proving itself to be off by a large percentage, and the prediction is not coming to fruition as they expected. When will we finally say their overall prediction ability is just wrong and get rid of these crap studies???

  4. The difference in long term average for Broome Airport since the 1940s as compared to the Post Office from the 1890s to the 1950s, is just 0.1C for the maximum and the minimum. No warming in more than 120 years!

  5. Any model whether it is financial, investment, risk or climate needs to be validated against actual data and differences explained. Because of the adjustments continually being made this is not always possible as the goal posts change so often. Thank you for your work

  6. Number of days above 35C is not a good indicator because in AUST major cities I have looked at there is seemingly no connection to GHG hypotheses. For Sydney Observatory and Melbourne Regional there is no significant change of this parameter from 1910 to present.
    See my new essay.
    And commentary “Press Release”

    A neat example of repetitive public widom not supported by observation over the last 100 years. Here the number of hot days each year has not been increasing. It looks like a random walk, that is not a good line to project forward as if there was a trend.

    • Geoff,

      Nice to hear from you. I like what you have linked to. The appeal to feeling hot is as you put it not very scientific and as you look more closely at the data there is nothing to support the proclaimed escalation in hot days other than a random walk as you put it.

      cheers, Basil

      • Of course everyone believes it is hotter. Weather reporters referred to very hot days but since most people work in air-conditioned offices or other work places these days when they emerge in the afternoon it does seem hotter despite being a normal summer day temperature. This lack of real awareness is occurring because of the use of air conditioning, not living in the real environment.

  7. I have a feeling the number of “hot” days per year in these tropical centres depends more on the amount of rainfall and humidity in the summer months compared to what the average global temperature is doing. Living an hour south of Cairns, I know the early 90s in Cairns were much drier than the late 90s as well as the summers of the early 2000s.

  8. What does all of this work and effort accomplish?

    Yes, I understand that one can track the temperatures… whoopee.

    The BOM and Acorn have been under fire for a number of years for willfully modifying temperatures.
    “Scandal: BoM thermometer records adjusted “by month”
    “Vanishing hot days of December 1931”
    “A mess of adjustments in Australian capital cities”
    “Australian BOM “neutral” adjustments increase minima trends up 50%”
    “The Australian Temperature Record Revisited: A Question of Balance”
    “ACORN-SAT: A Preliminary Assessment”

    Which makes it odd to have a “fill in” spreadsheet tracking BOM/Acorn temperatures to see if they calculate a trend between 10%-90% boundaries?

    About those 10%-90% boundaries?
    What if the future trend hugs the 10 percentile line?
    From the existing trend lines alone, a 10th percentile could very well be a normal trend. Considering these locations, previous heat waves could very well make a 20% trend line normal.
    Nor is the 10 percentile line proof positive for global warming.

    There appears to be a curious assumption that CO2 emissions are cause for future trends. Have all other influences been identified and accounted for? e.g. UHI?

    It is curious that the tracked temperatures all begin in 1980, yet each of these stations have long records.
    Long records with substantial ranges of variability.

    No matter what someone’s idea of tracking a twenty year trend, temperatures that fall into natural variability ranges may be solidly natural, no matter how frequently those temperatures occur for short periods.

    My apologies Dr. Beamish, you have spent quite a bit of time and work on this article.

    Let’s ask a slightly different question.
    There have been many wild predictions regarding temperatures and trends since the beginning of the CO2 debacle?
    What is the point of tracking future temperature records when none of the predictions over the twenty five years have come true? Nor have these prediction failures dinged the plans or actions of the climate unhinged.
    Mankind has not deciphered all climate components, let alone tracked enough honest history to understand Earth’s cycles beyond a few months.

    Our hopes are pinned to Earth’s recovery and warming since the ‘little ice age’. Even a short relapse into colder temperatures would be disastrous; yet the CO2-loons clutch our hair shirts and shriek CAGW disasters over very ordinary weather and temperatures.

    Let us hope the warming continues.

  9. I’m sceptical of projections of higher maximum temperatures by the BoM in the monsoonal areas of Australia (Darwin, Broome) for the simple reason that in a warming world the monsoon will get stronger and longer, and maximum temperatures are lower during the monsoon.

    The highest monthly average max temps in Darwin occur in October and November (the equivalent of April and May in the NH) because of the monsoon after those months.

    I’d conclude that a model projecting lower temperatures wouldn’t send the ‘right message’. Thus necessitating a model that projects warmer temperatures despite the physical reality.

  10. Like many, I like to have a look at the data or base article referred to if time permits, but often time does not permit.

    In an article such as this which is looking at a projection based upon “2030 Medium emission scenario” it would be useful and good practice to detail what that emission scenario is. What does it claim about CO2 emissions?

    One needs this explanation since one needs to consider how realistic the projection is, and if observational data proves the projection wrong is this explained by the fact that the 2030 Medium emission scenario did not pan out?

    What if the 2030 Medium emission scenario underestimates CO2 emissions, and yet when the observational data is in (2030/31) the number of hot days is well below projection? That would demonstrate that the models are even more worthless.

  11. Why chose 35C (95F) as “hot”? Living in Denver, we regularly see temps in the mid and sometimes upper 30C (95F to 100F) range. While it’s no picnic, it can be a lot worse!
    I’ve been in Phoenix when they closed the airport because the planes aren’t certified to fly in roughly 52C (125F). That was hot!

  12. Basil,

    “As each five years of data becomes available it should become readily apparent whether the model projections are either validated or not.”

    It seems to me (nobody special), that this is more appropriate/logically sound;

    *As each five years of data becomes available it should become readily apparent whether the model projections are either invalidated or not.*

    Validation is more demanding than a five year correlation with observations, no?

  13. Frankly, I can’t see what the authors of the original paper were setting out to prove with their crappy models. If the central premise of a supposedly warming world is increasing entrapment of heat – on account of the deadly killer gas and well-known plant food – why are they only focusing on temperature? The heat content of air is measured by its enthalpy, which includes the sensible and latent heat components of the water vapour element.

    Given that the enthalpy of air at 30C and 60% relative humidity is nearly the same as air at 35C and 40% humidity (70.50 kJ/kg vs 70.94kJ/kg respectively), a temperature reading alone tells only half the story.

    I’ve looked through the last year’s BOM daily measurements for Darwin, and the hottest days (35+) are almost all associated with lower humidity, and the coolest days (27-29) with high humidity. Measuring the temperature therefore basically just tells you which way the wind is blowing. The same is true for most tropical locations, where despite receiving the most potential insolation, the humidity (ergo also clouds and thunderstorms) keeps max temperatures lower than in the subtropical arid zones, where deserts live.

    Is it just me, or do the disaster freaks overlook basic physics because they don’t understand it, or have they been instructed to forget about humidity because “it’s the same, on average”. It ain’t.

    • Bob Highland,

      Is it just me, or do the disaster freaks overlook basic physics because they don’t understand it, or have they been instructed to forget about humidity because “it’s the same, on average”. It ain’t.

      It’s just you; specific humidity is expected to continue increasing with warming. Sherwood and Huberb (2010) do you one better by remembering some human physiology, and discuss the implications of wet bulb temperatures exceeding 35 °C.

      Somehow I doubt you’ll be impressed by their findings:

      We conclude that a global-mean warming of roughly 7 °C would create small zones where metabolic heat dissipation would for the first time become impossible, calling into question their suitability for human habitation. A warming of 11–12 °C would expand these zones to encompass most of today’s human population. This likely overestimates what could practically be tolerated: Our limit applies to a person out of the sun, in gale-force winds, doused with water, wearing no clothing, and not working. A global-mean warming of only 3–4 °C would in some locations halve the margin of safety (difference between TW max and 35 °C) that now leaves room for additional burdens or limitations to cooling. Considering the impacts of heat stress that occur already, this would certainly be unpleasant and costly if not debilitating. More detailed heat stress studies incorporating physiological response characteristics and adaptations would be necessary to investigate this.

      If warmings of 10 °C were really to occur in next three centuries, the area of land likely rendered uninhabitable by heat stress would dwarf that affected by rising sea level. Heat stress thus deserves more attention as a climate-change impact.

      The onset of TW max > 35 °C represents a well-defined reference point where devastating impacts on society seem assured even with adaptation efforts. This reference point contrasts with assumptions now used in integrated assessment models. Warmings of 10 °C and above already occur in these models for some realizations of the future (33). The damages caused by 10 °C of warming are typically reckoned at 10–30% of world GDP (33, 34), roughly equivalent to a recession to economic conditions of roughly two decades earlier in time. While undesirable, this is hardly on par with a likely near-halving of habitable land, indicating that current assessments are underestimating the seriousness of climate change.

  14. An interesting time period that has been selected for Cairns – as someone who moved to Cairns in 1984 whilst working in the Airline industry, I can’t imagine a more propitious time for people of the Global Warming persuasion! In February, when I began work there we handled four domestic flights daily (Ansett) and one small international jet flight per week, to Timika for a mining company. The Stephenson’s screen measuring temperature was situated just behind my building, under a large palm tree and adjacent to the control tower.

    Later that year the new airport was opened and Cairns literally exploded as a tourist destination, the growth was phenomenal, to the point where my facility was handling twelve domestic flights daily and sixty international weekly. The projections for growth meant that the airport building meant to handle traffic for the next twenty years had to be revised and and a new international terminal, together with associated runways, roads, parking areas etc., all were added. Increasing the areas of concrete and tarmac exponentially.

    It’s my understanding that the instrumentation for measuring temperature were also moved from it’s previously shaded position to a far more exposed area on the opposite side of the runway where all the new buildings, car parks and aircraft were situated.

    We have read much about the BOM and it’s propensity to “homogenise” temperature records, it would be most interesting to know what allowances (if any) were made for these dramatic changes in potential for influence as a result of all this extra concrete, building and activity by extra jet engines post 1984.

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