I tried twice yesterday to submit a message to the page http://jennifermarohasy.com/blog/2009/06/hot-city-or-global-warming/?
cp=all#comments

I tried again today but the site told me I’m trying to submit duplicate content. I’m not sure if the message has appeared on some other page or not at all.

Whichever, below is the message I’m trying to submit …

It’s interesting to see the min and max temps from different Victorian locations over the past 150 years but it should be noted that data before the Stevenson Screen (~1910) isn’t considered reliable for comparison with years hence. That’s the BOM’s position and, although it’s debatable whether the screen created a negative or positive min and/or max temp bias against the earlier records, I think the valid comparison is since the 1911-1940 bracket. If anything, that suggests a slight fall in temps across the five regional locations in Victoria.

For WA figures extracted from the BOM databases, see http://www.waclimate.net

WA in summary…

1876-1899 vs 1979-2008 from 13 locations – average min up .41 degrees and max up .34 degrees

1876-1899 vs 12 months to May 2009 from 13 locations – average min down
.51 degrees and max up .45 degrees

There are 20 WA locations that have both pre and post 1910 records.

~1900 vs 1979-2008 from 20 locations – average min up .44 degrees and max up .48 degrees

1910-1939 vs 1979-2008 from 20 locations – average min up .7 degrees and max up .5 degrees

There are 32 WA locations with consistent records from ~1900 to the present day

~1900 vs ~2000 from 32 locations – average min up .56 degrees and max up .52 degrees

~ 1900 vs 12 months to May 2009 – average min down .12 degrees and max up .75 degrees

The WA data suggests a rise in maxima and a drop in minima, particularly over the past decade and possibly reflecting the reduced rainfall cloud cover in the south of the state – albeit at odds with a huge increase in rainfall in the north.

Perth, which is by far the state’s biggest heat sink, had the highest averaged increase in mean maximum temperature among all 32 locations, including pre-1910 data, over the hundred years (1.7 degrees C).

A comparison of the five WA locations with a population above 20,000 and the remaining 27 locations below 20,000 suggests the heat sink adds between .5 and 1 degree C.

Cheers!
Chris Gillham

Average temperature trends across Western Australia http://www.waclimate.net

Scribeworks
http://www.scribeworks.com.au

From memory much the same as you are finding I can’t dig it up since it was all on a hard disk on a computer that found it’s way to the nature strip two cleanups ago. I’ve kept the disk so I may see if I can retrieve the data. My focus however was more on which stations were being kept for the statistics (GISS) and which dropped out over the years. IIRC more stations from aerodromes in rural areas were kept and others dropped out.

Michael,
Your results mirror my own jottings and so I presume you have used the BOM’s ‘Climate statistics for Australian locations’ data (30 year statistics). I just compared 1911-1940 temps to 1971-2000 temps for smaller country towns (to try to eliminate UHI).
To answer your question, max temps range from no change to 1.0C below over the past 90 years and minimums range from no change to 1.2 above. There are exceptions such as Griffith (0.1C max increase) with Balranald, Deniliquin and Murrurundi showing decreases in minimum temps but I am finding the majority of the 20 country towns I checked fit this profile (I haven’t check coastal towns as yet).
Jan,
What were your conclusions from your work you did 4 years ago?
I only began to take an interest recently when I read about all these records supposedly being broken, only to check back and find that far warmer periods existed in the past (BraveNewClimate is good at that).
The 1981-2010 averages will be interesting when they become available.

Yes, people keep rediscovering the facts. I think it is wonderful. And everyone comes from a slightly different perspective.

Michael,

I’ve emailed you with some suggested changes to the next piece. I am a bit short on pieces with some data at the moment, so am keen to post ASAP.

Indeed it has actually been more stable than we aim to get our industrial temperature controllers, which we generally do to the nearest degree c. Though I’m sure we could do better if we needed to.

You guys are finding much the same as I did 4 years ago. In a way it’s discouraging to have to go over the same ground over and over again.

Yamba

1881-1910 15.5—24.3—19.9
91-20 15.5—23.5—19.5
01-30 15.3—22.9—19.1
11-40 15.3—22.8—19.1
21-50 15.0—22.8—18.9
31-60 15.0—23.0—19
41-70 15.0—23.0—19
51-80 15.2—23.0—19.1
61-90 15.4—23.0—19.2
71-2000 15.5—23.2—19.4

certainly a dip mid century and a rise back up towards the temps at the start of the 20th century

Gabo island

1861-1890 11.6—19.4—15.5
71-00 11.5—19.2—15.4
81-10 11.4—118.4—14.9
91-20 11.8—17.7—14.8
01-30 12.2—17.4—14.8
11-40 12.3—17.5—14.9
21-50 12.2—17.4—14.8
31-60 12.2—17.2—14.7
41-70 12.3—17.2—14.8
51-80 12.5—17.4—15.0
61-90 12.5—17.7—15.1
71-2000 12.4—18.0—15.2

again a dip in the middle part of the century followed by a rise not quite back to the late 19th century

Broken Hill

1891-1920 11.7—24.6—18.2
01-30 11.8—24.3—18.1
11-40 11.7—24.3—18
21-50 11.7—24.3—18
31-60 11.5—24.0—17.8
41-70 11.8—23.8—17.8
51-80 11.9—23.7—17.8
61-90 12.2—23.8—18
7-2000 12.3—24.0—18.2

looks like a substantial rise late in the 20th century but in fact its the same pattern witha dip in the middle of the 20th century and a rise back up to in the case the saem as the start of the 20th century

I also have data for Parkes – shwos exactly the same thing and for Golburn which shows a dip the a rise toa bout 1960 and then another dip from 13.7 av in 1890 to a trough of 13.3 in the 20’s and 30’s then a peak of 14.3 in the 50’s and a drop to 13.9 in the 70’s.

I am getting tired of typing tables.
However what all these sites seen to me to show is a very stable temperature record moving around by a few tenths of a degree but with late 20th century temps very close to late 19th century temps. Hardly a monotonic trend and certainly not anywhere near 0.1C per decade (1C per century).

I still can’t reconcile this with the BOM digested results.

I can’t understand [or maybe I can] why a lot of the 19th century data was thrown out on the basis that the old thermometers were on verandahs and not housed in stevenson screens and therefore hot-biased.
Often those verandahs were where the old open topped canvas water bags and various other water wicking devices designed to cool everything possible, were kept. Some verandahs even had two layers of chicken wire with spinifex needles in between wicking up water from a trough around the bottom. The air passing through would cause evaporation and create a delightful microclimate. It was common to hear someone say, “it’s 112 in the bottom of the waterbag”.
I doubt that those old verandah readings would have been biased towards hot.