Ken Stewart, July 2010
The last State to look at is Australia’s first State, New South Wales. NSW is the oldest, most populous, and richest in the Commonwealth. Although their State of Origin record is pretty dismal of late, they outclass Queensland in one field- adjustments to their temperature record.
The Australian Bureau of Meteorology (BOM) develops its climate Trend Maps and Time Series graphs form 100 sites nationwide, comprising the High Quality Australian Site Network. 17 of these are in New South Wales.
As you can see, BOM declares a warming trend of 0.08C per decade, or 0.8 degrees C for the last 100 years.
I have now completed (almost) the first independent study of the High Quality Australian Site Network, and as part of that project have analysed the data from the New South Wales sites. I averaged maxima and minima for all stations at each site, then compared with the High Quality means. Please note: at this stage I have only looked at the non-urban sites, as BOM says the Urban sites are excluded. BOM has adjusted the raw data to clean up errors and discontinuities, by a method described in Part 1: Queensland. A spokesperson for BOM has asserted that:
“On the issue of adjustments you find that these have a near zero impact on the all Australian temperature because these tend to be equally positive and negative across the network (as would be expected given they are adjustments for random station changes).”
Based on an average of trends at these sites, there is a 36% warming bias!
Once again you will notice that there are 4 stations whose trends have been reduced, 3 which are essentially unchanged, and 10 warmed.
You will also notice that the State trend (0.8) is obviously not the same as the above calculation. It must be derived by averaging all the data and then finding the linear trend. Here is a graph of the raw and HQ record for all 17 non-urban stations and the resulting trend:
This shows the raw trend at 0.5 degrees C per 100 years, and the High Quality trend at 0.75 degrees. BOM rounds this to 0.8. That’s a warming bias of 60%!
This study is only looking at the 100 stations that BOM uses for the official climate record, that is, the non- urban sites. BOM does not use urban sites, and until now I have assumed this is because they want the High Quality record to be free from contamination by such things as Urban Heat Island effect. Never assume. It is easy to compare the average trend of NSW as a whole (0.8 C) with that of the Urban sites. The average of the Urban stations is less than 0.6 degrees C per 100 years! In other words, they are warming less rapidly than the non- urban sites. Interesting- I wonder why? That will be the subject of another study.
But there is another peculiarity about NSW. Many of the High Quality data records have the final few years missing. Have a look at this plot of the number of stations with raw and adjusted data available in each year:
The mid- century loss of raw data is plainly obvious- this occurs throughout Australia. But you also see that BOM has not continued the High Quality data to 2009 in many cases- indeed in 2007 a third of the HQ record is missing!
Let’s look at the individual stations.
BOM slightly cools this record. Note BOM also corrects the 1931 plunge.
But the HQ data has been simply combined and adjusted to show a warming of 0.7C! The raw data spliced in this way shows only 0.3C/ 100 years. I have gone with this even though I disagree, to compare the two.
But this time BOM has decreased the earlier data to match. As they didn’t do this at Bourke, to be consistent I have kept the raw data. What’s good for the goose as they say. Warming increased from 0.5 to 0.9C.
Tenterfield is near the Queensland border in high and cold country. It is the town where Sir Henry Parkes made a famous speech in favour of Federation, and the home of entertainer Peter Allen. The raw data has gaps, but is comparable with Wallangarra only 16km away on the border, and is flat- about 0.15C warming.
This is a rare example of a record being adjusted to correct UHI: from 1.15 to 0.5. Well done, BOM. But why the difference in temperatures?
I spliced Kooringal less 0.75 (the average difference) with the AMO to get a slope of 0.4C. BOM distrusts the AMO data from 1942 to 1969 and continues the slope backwards to 1910, to produce a warming of 1.3C / 100 years:
When all non-urban stations in the state are averaged, the raw trend is 0.5C/ 100 years, the High Quality trend is 0.75C, which gives a bias of 50%. BOM rounds the 0.75 to 0.8, which makes it even worse- 60%.
Strangely, the average of the HQ Time Series Graphs for the Urban sites show less than 0.6 C warming per 100 years .
Four stations are cooled, three are left almost as is, and the other 10 have been warmed.
The High Quality record leaves out many stations in the last decade- 2007 has one third missing.
“High Quality” is not an apt description for this record.
I have now completed this check of the High Quality sites which are used to produce the official Australian temperature record. There appears to be a nation-wide warming bias of 33%. “Near zero impact”? This will be the subject of the final post in this series, in about a week.
Many thanks to “janama” for his earlier work and encouragement, and Lance for assisting with downloads.