BoM claims record Perth heatwaves – numbers suggest not so simple

IMHO the BoM in Perth is gung-ho when it comes to claiming any records to do with warming. So I have taken a few hours to compare this summer to March heatwaves with those from 1977/78 – in each case comparing the Perth station with, sites at Perth Airport, Pearce RAAF, York and Merredin.
Taking the BoM definition of a Perth heatwave as 3 days over 35C.
I assembled daily max T for the months Dec to Mar incl for 1977/78 and 2011/12 – for the above sites. Note in 1977/78 Perth data was recorded at “9034 Perth Regional Office”, York was “10144 York Post Office” – the others were “9021 Perth Airport”, “9053 Pearce RAAF” and “10092 Merredin”.
In 2001/12 Perth data was recorded at “9225 Perth Metro”, Perth airport, Pearce and Merredin were unchanged and York was at “10311 York”.
I condensed my data down to only those days included in the “official” Perth heatwaves for the two periods and there are 27 Perth heatwaves days in both 1977/78 and 2011/12 Dec to 11 March so far – note Pearce RAAF had missed readings on days in 1977/78 and Merredin had 2 missing. In 2011/12 Pearce had 1 missing day.
Next I averaged the temperatures for these various places for the 27 day period of the Perth heatwaves.
Note in the ABC article linked above; how the BoM make big of the fact that in 2011/12 Perth has 8 heatwaves while only 7 were recorded in 1977/78.
In fact in 1977/78 there were only four 3 day events but there were two 4 day events and a seven day event.
While in 2011/12 so far we have had six 3 day events and one each of 4 and 5 days. So heatwaves tended to be longer in 1977/78 – a point the BoM did not tell the pliant ABC.

The other interesting point that emerged was that while Perth Regional Office was slightly cooler in 1977/78 than Perth Metro was in 2011/12. All the other sites were warmer in 1977/78 compared to 2011/12.
This supports my contention that the BoM is not correct in assuming that Perth Metro is equivalent to Perth Regional Office. The BoM is also not correct in always ignoring the fact that Perth has a growing urban heat island (UHI).
The BoM should take far more care reporting pro-IPCC conclusions hastily drawn from their imperfect data.

10 thoughts on “BoM claims record Perth heatwaves – numbers suggest not so simple”

  1. No mention of the unusually cool summer in nearby Meekatharra.

    Just 5 x 40 degree days this year (2012)

    Only 1933 , 1955 and 2000 are similar.

    Added by Ed: You are correct Ripper – vast areas of WA have been anomalously cool for all of summer – Dec to Feb see the huge areas of green on these maps on right hand panel.
    Note the miniscule areas of actual warmth clinging to the coast compared to the much larger areas the BoM predicted warm. The BoM are shameless pro-warming, unbalanced propagandists.

  2. Warwick thank you for this timely post
    already Ch 10 is trumpeting record for Perth

    I don’t know if you’ve heard about what has happened to Jennifer Mahorasy
    full story here

    MEDIA Watch contacted me on Friday with a barrage of questions concerning my work on the need to restore the Murray River’s estuary. Their line of questioning suggested that I was misleading the Australian public on the important issue of water reform in the Murray Darling. Indeed, the implication was that I am but a stooge for vested interests.

    It appears Media Watch is contemplating asserting or implying that my professional judgement and integrity as a scientist has been influenced or corrupted by personal financial gain. Accordingly, I have sought legal advice on the matter, and include this in my full response that can be downloaded here:

    copy of my comment on Catallaxy

    Token; I agree the media watch focus on Jennifer Marohasy is an example of bias

    I don’t recall Flannery, Garnaut, the CSIRO or BOM being asked to answer questions

    And why not; Jennifer answered the questions very well; how well would Flannery, Garnaut, and the others do.

    for an example of the trumpeting by the media and BOM of ‘record Perth heatwaves’ see

    Will media watch now send questions to BOM; if not; why not?

    Added by Ed: It was pleasing indeed to see how the return broadsides by JM destroyed the Mediawatch case.
    What a bunch of biased Govt paid meddlers Mediawatch are.

  3. I also notice that Perth Airport only had 7 heatwaves over the same period. Perth Metro records show a heatwave from 8th – 10th Feb whereas Perth Airport records 34.8C on the 8th so making a two-day +35C, not 3.
    Perth Metro has been only operational since 1994 so using this one station to compare with a long-running station such as Perth Airport is not quite kosher.
    Perth Airport has some 31 days of above 35C during Dec 1977 – Mar 1978 which is again different to the now-closed Regional Office. The station records 2×3 day, 1×4 day, 1×6 day, 1×7 day and 1×8 day event – only 6 heatwaves. This was because the 29th Jan was recorded at 35.2C (making a continuous heatwave from 25th Jan to 1st Feb) whereas Perth Regional recorded only 33.0C thus breaking it into 2 separate heatwaves.
    Maybe a heatwave should be 3 consecutive days over 35C and then start again. You could have the situation where in one month each day could be over 35C and this would only count as one heatwave.

  4. A recent BOM media release referring to a paper presented at the Australia – New Zealand Climate Forum in Hobart (October 14, 2010) admits it formulated its calculations incorrectly.

    BOM concedes that daytime temperatures in Aussie cities are warming more rapidly than those of the surrounding countryside and that this is due to the cities themselves. In effect, the admission undermines all prior claims that such warming is principally due to man-made emissions trumpeted in the similarly discredited “greenhouse gas theory.”

    Skeptical researchers have long argued that little or no weighting has properly been ascribed to the UHI phenomenon; this apparent U-turn may signal the demise of the now discredited official adjusted Australian temperature record.

    Bureau climate scientist, Belinda Campbell, admits “we’ve known for a while that city night time temperatures have been warmer because the heat’s retained after sunset just that much longer than the countryside, and that city daytime temperatures have been warming too. But what we didn’t know was whether city daytime temperatures were also warmer because of the urbanisation or whether it was due to the overall warming of the planet associated with the enhanced greenhouse effect. We can now confidently say that the reason our cities are warmer and warming faster than the surrounding countryside during the day is because of the urbanisation, the fact that all those offices, houses and factories absorb the heat and retain it a little bit longer.”

    See the full discussion on BOM’s belated discovery on the excellent WUWT blog.

    has this paper been peer reviewed yet?
    Note by Ed: I would bet Val that the Belinda Campbell effort is in no danger of disturbing the intray of the Editor of any Learned scientific journal.
    But I can be wrong.
    However the BoM has decades long history of sitting on findings that disturb the tranquility of BoM mythology.

  5. Hallelujah! Somebody with climate knowledge is seeking to set the record straight and counter the incompetence of the WA media.

    Perth’s monopoly weekday press, The West Australian, started this heatwave sensation (lead story ABC TV News last night) on March 3 with a story that Perth might actually have some more hot weather in early March (amazing!), reporting at that stage that maxima need to reach 35C for five consecutive days to be considered a heatwave.

    The BoM says there is no clear definition of “heatwave” but over the past week the media has been put straight with a definition that three consecutive days need to reach 35C. Debatable use of the word but if we’re talking about a “record” eight times since the Perth max hit 35C for three days since November, fair enough.

    However, sorting through the muddle of media reporting, yesterday’s story in the Sunday Times about Perth’s record current heatwave (?) had a BoM spokesman saying: “The all-time record is 10 heatwaves. That was recorded in February 1975 and 1988.”

    Say what? It’s hoped the BoM spokesman was referring to the two periods of 10 consecutive days in Feb 1975 and Feb 1988 with max above 35C … 35.5, 38.3, 39.6, 40.9, 39.7, 40.7, 35.5, 36.8, 36.4, 35.6 in 1975 and 35.9, 35.8, 36.5, 37.4, 37.6, 37.9, 38.1, 39, 38.9, 38.8 in 1988.

    What the BoM and media aren’t into reporting are irrelevant things such as the fact that last February the mean max at Perth Metro was 34.2C and this February it was 31.1C – which is .4C below the long-term Feb mean max of 31.5C (1961-1990 baseline mean). The mean monthly max for February 1975 was 34C and in 1988 it was 33.9C.

    Where’s that headline? “Perth enjoys below average February”

    Instead we have headlines such as “Endless Summer” a couple of weeks ago in the Sunday Times wherein the BoM declared Perth’s summer average max at 31.8C, “slightly less than the record 32C summer averages of 2010-11, 2009-10 and 1977-78.”

    December 2011 – 30.5C, January 2012 – 33.5, February 2012 – 31.1 / Average = 31.7C, not 31.8C. Never let the facts get in the way of a good climate change.

    Mind you and as Warwick points out, Perth temperatures before 1994 were recorded several kilometres south in the central city close to the Swan River, and before 1967 they were recorded atop Mt Eliza (see, so when referencing the 9225 Mt Lawley site, Perth’s temperature history only really begins in 1994.

    It has been hot at Perth Metro since 2008 (see the 2009 BoM bug – and we’ve had well above average days over 35C, but a Jan-Feb-Dec annual look at the number of 35+ days during past years shows the record still stands in 1979:

    Mt Eliza

    1898 15
    1899 14
    1900 13
    1901 15
    1902 10
    1903 1
    1904 17
    1905 13
    1906 7
    1907 8
    1908 11
    1909 12
    1910 18
    1911 6
    1912 6
    1913 13
    1914 12
    1915 13
    1916 16
    1917 8
    1918 9
    1919 13
    1920 9
    1921 21
    1922 24
    1923 8
    1924 9
    1925 9
    1926 3
    1927 16
    1928 14
    1929 5
    1930 16
    1931 13
    1932 23
    1933 11
    1934 20
    1935 16
    1936 11
    1937 5
    1938 8
    1939 9
    1940 8
    1941 16
    1942 12
    1943 12
    1944 3
    1945 14
    1946 16
    1947 4
    1948 9
    1949 7
    1950 10
    1951 15
    1952 8
    1953 15
    1954 8
    1955 14
    1956 17
    1957 13
    1958 13
    1959 15
    1960 12
    1961 8
    1962 23
    1963 27
    1964 16
    1965 10
    1966 22

    Wellington St

    1967 13
    1968 15
    1969 15
    1970 10
    1971 17
    1972 11
    1973 28
    1974 12
    1975 24
    1976 25
    1977 20
    1978 20
    1979 30
    1980 18
    1981 13
    1982 10
    1983 14
    1984 11
    1985 16
    1986 20
    1987 17
    1988 10
    1989 20
    1990 18
    1991 13
    1992 19
    1993 16

    Mt Lawley

    1994 15
    1995 16
    1996 19
    1997 21
    1998 16
    1999 25
    2000 19
    2001 5
    2002 19
    2003 16
    2004 21
    2005 9
    2006 17
    2007 13
    2008 25
    2009 28
    2010 23
    2011 29

    Thanks to the media, most West Australians think we’ve just suffered through a scorching year as climate change encroaches. That’s possibly because no story yet published has informed them that across WA, the mean annual temp in 2011 was .1C below the historic normal.

    It was a below average year across WA, but not in the very warm parallel universe of the BoM and a clueless media.

  6. My physics tells me that it’s not the temperature at one single point on the map that counts but the total energy measured all over the country, and if one considers this, Australia is caught in deep freeze.

  7. here’s the Oz

    PERTH is sweltering through a record-breaking eighth heatwave.

    The Bureau of Meteorology defines a heatwave as three consecutive days at or above 35C.

    The record was reached during the weekend and today the temperature remained high, peaking at 40.6C.

    Maximum temperatures for the previous three days were 38.9C on Friday, 39.5C on Saturday and 41.4C yesterday.

    It is the third time that Perth has recorded four consecutive days above 38C in March, the bureau says.

    The other occasions were between March 12-15, 1922 and March 7-10, 2003.

    Only once before has Perth previously recorded two heatwaves in March and that was in 1988.

    The bureau says the previous record of seven heatwaves in the summer/autumn season happened in 1977/78.

    . .
    Perth has also experienced its hottest start to March on record.

    The mean daily maximum temperature for March 1-12, 2012 was 35.9C, breaking the previous record of 34.7C in 1979, the bureau says.

    Temperatures are expected to drop down to 30C by tomorrow and hover around that temperature for the rest of the week.

  8. 6. Chris Gillham Says: March 12th, 2012 at 5:24 pm

    “It was a below average year across WA, but not in the very warm parallel universe of the BoM and a clueless media.”

    The media isn’t clusless Chris, it is complicit.

  9. RAAF Pearce would have been missing most weekends in 1977/78. I was a meteorologist on base in 1972-1975 and AFAIK things didn’t change until a fair bit later. We used to work Monday to Friday except for the very odd occasion.

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