Bourke: How 1km of land clearing can warm a million square miles

Yet again, we have to ask: does the Bureau of Meteorology care about Australia’s long term climate trend? Are they even trying?

Bourke could be one of the top ten most influential temperature sites in the world, mostly by virtue of being miles from anywhere, and used to homogenize a large slab of the land mass of Australia. Bill Johnston documents how changes to the site create most of the temperature trend.

The Bureau of Meteorology’s fancy magical and secret homogenization protocol does not detect changes that obviously affect the temperature (like the clearing in the photo below). But sometimes the BoM make “corrections” because of site changes that don’t appear to have mattered. Is it conveniently selective or just inept?

The BoM don’t even document major site changes a lot of the time. Even iconic sites that affect huge areas are badly managed. Someone got the tractor and plough and cleared the vegetation. As usual, a citizen scientist, a volunteer, documents it (along with a suite of other site changes).

The town is the last outpost of civilization, so infamous it has it’s own cliche: “The back of Bourke”.  If there was a perfect thermometer in Australia, this place would vie for the top spot with records going back to 1871, on the crossroads to nowhere and one of the last almost untouched towns –historic, but not urbanized enmasse. And it is an official ACORN site, considered one of the best quality records in Australia. Bourke is at the crossroads to Australia’s outback  and is one of the last almost untouched towns –historic, but not urbanized enmasse.

But thanks to Bill Johnston, we now know that even out here the long hand of incompetence and bias has romped through the data. Again, Bill documents a site that has been watered,  moved, gone electronic, had a new screen, shifted to the airport, and then just in the last few peak years — as climate change became “life or death” — someone cleared the ground all around it and no one at the BOM noticed.

In a Bermuda-triangly type mystery, the station went “electric” but instead of getting better data, for a few years the temperature was only recorded in whole rounded integers. (So much for the tenth of a degree of accuracy, eh?) Plus two or three weeks of data went missing each year, and the site failed performance checks twice.

The wonderbar Technical Advisory Forum set up to boost confidence in the expertise of the BoM didn’t investigate this in 2015. Being consistently irrelevant, they also didn’t investigate in 2016 or 2017 either. What looks like a whitewash, smells like a whitewash…

Likewise, two-rounds of expert peer-review fail to address such obvious problems in the Bureau’s homogenisation methods?

Bourke is so hot it was the place they sent trains to in 1896 to rescue people from a monster heatwave.  Bourke is used to homogenise stations like Alice Springs which is 1,400km (860 miles) away. Does this little clearing “heat” a million square kilometers of records? It’s possible.

As usual, Johnston’s short post here is backed up by a longer PDF file which outlines his detailed years of research.

One Nation’s Senator Brian Burston is presenting this information and the paper to the Senate Estimates on Monday morning. Questions need to be answered.

— Jo

 

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Welcome to the back of Bourke where they make the weather warmer

A science post by Dr. Bill Johnston[1].

Main points

• The climate at Bourke and surrounding sites hasn’t changed. There is no temperature trend, no increased frequency of extremes and no trend in extremes.
• As no sites have stayed the same, Australia’s long-term weather records are not useful for tracking trends in the climate.
• Arbitrary homogenisation adjustments coerce data to agree with models. Comparative homogenisation is biased and should be abandoned.

Introduction

Bourke in northwestern New South Wales is synonymous with ‘the bush’; Clancy of the overflow; crows flying backwards to keep dust out of their eyes and mozzies big as chooks…. While caravans and mobile-vans roll-in during winter when its cool and dry they stay away in droves in summer. Rainfall is a low 336 mm/yr; the driest was 86 mm in 2002 and the wettest, 854 mm in 1950. Runs-of-months with zero rain are common and the drier it is the hotter it gets. Irrigation along the Darling River and dryland grazing of cattle, sheep and goats (and tourism) supports the town’s 2,000 people.

The history of the place

Starting in 1871 Bourke ranks with Sydney Observatory (from 1859), Melbourne (1856), Perth Observatory (1897), Hobart (1882) and some lighthouses (Cape Otway (1865), Yamba Pilot Station (1877) and Nobbys Head (1867)) as one of the longest continuous weather records in Australia and one of the longer datasets in the Southern Hemisphere. It is also one of 104 non-urban ACORN-SAT sites (Australian Climate Observations Reference Network – Surface Air Temperature) used to calculate Australia’s warming.

Site and instrument changes effect measurements. The environment surrounding the site has not remained consistent; the Stevenson screen has not stayed in the same place and equipment used to measure temperature has changed also.

Observations were first reported from the telegraph office and after it burnt down on 8 November 1874 the office moved to another building, which it shared with the post office. A new post office (with residence) was built in 1880 in Oxley Street several allotments east of the courthouse, which is on the Richards Street corner (Figure 1). The second storey was added in 1889 and modifications continued until telegraph and postal services merged to form the Post Master Generals Department in 1901.

The large 230-litre Stevenson screen installed in 1908 moved at least once in the post office yard and from the 1950s it was shaded and surrounded by watered lawns. It was replaced (and probably moved) in 1964 and due to continuing “vegetation problems” observations ceased there in August 1996.

Thermometers were observed in another 230-litre screen beside a dusty track at the second airport north of town in 1994. That site was superseded by an automatic weather station (AWS) 700 m away in 1999, which used a small 60-litre screen and which reported whole-degrees before 2002. The many temperature values that were culled shows the AWS was frequently over-range, probably because its rapid-sampling probe operating in the small screen recorded flurries of warm air that would not affect thermometers housed in large screens; or that due to calibration problems it was prone to spiking on warm days.

The AWS site was ploughed-around in 2013, which made it even hotter

Understanding data requires careful analyses and research. Step-changes detected using independent statistical tests are aligned with reports in newspapers and archives (National Archives and National Library of Australia); museums like the Airways Museum at Essendon and the RAAF Museum at Point Cook; and checked using historic aerial photographs and Google Earth Pro (Figure 2).

Bourke temperatures are hotter now than in the past because of site changes, not the climate.

Because sites change, data collected to describe the weather are often not useful for benchmarking trends in the climate. Shade, watering and the new building caused changes at the post office and the hotter it was the more watering was probably done to cool the place down. Daytime temperature is warmer at the airport especially in summer and Google Earth Pro satellite images show the current AWS site was ploughed around before 2013, which according to Blair Trewin[2] is “Australia’s hottest ever year”. The most recent ‘record’ temperature at Bourke (48.3^oC on 12 January 2013) is due to ploughing not the weather.

 

Its hot when it’s dry and cool when its not and careful analysis outlined in the attached Bulletin shows the climate of Bourke hasn’t changed. Temperature trends and frequency of upper-range extremes has not increased. The AWS-site is neglected; out-of-range values are selectively culled because electronic thermometers housed in dusty 60-litre Stevenson screens spike randomly on warm days.

Recent temperature records at Bourke are due to ploughing; those at Wanaaring are due to the small screen moving from behind the post office, where the lawn was watered, to beside the dusty track to the tip in 2003. Brewarrina’s data are warmed after 2002 by new hospital accommodation; while at Cobar data are affected by urban encroachment. Like ploughing, establishing AWS at the hottest sites imaginable (Figure 3) is just another trick. While the Bureau warms the data the climate hasn’t warmed or changed.

 

Homogenisation

ACORN-SAT is the sum of its parts and Bourke is just another example of where arbitrary changes create trends that don’t reflect local weather. Recent claims of record warming are not supported by individual site data. (Bourke homogenisation is outlined in Part B of the Bulletin.)

Across the network site-changes are not rigorously documented, some are ignored and some that make no difference are adjusted as though they did. Furthermore, selecting faulty (correlated) data to adjust ACORN-SAT datasets results in bias. The default position that unexplained data-changes are attributed to the climate allows climate-changes to be specified in advance and data to be homogenised accordingly.

Australia’s ACORN-SAT temperature datasets are riddled with problems. The process is opaque; lacks statistical control; synchronous inter-site changes such as replacing 230-litre screens with 60-litre ones and thermometers by AWS at infrequently serviced sites beside dusty tracks and in paddocks at airports, are propagated across the network by the process. Thus few ACORN-SAT datasets are independent of collective problems. Using comparator data that are not homogeneous to adjust faults in ACORN-SAT has no merit and should be abandoned.

Conclusions

• The Bureau’s ardent support of climate warming has overtaken its job of monitoring the weather. Replacing observers with AWS and 60-litre Stevenson screens beside dusty tracks, which are checked at most places less than once per year has warmed Australia’s climate.
• It’s always been hot at Bourke especially when it’s dry. The climate hasn’t changed; temperatures have not increased nor are extremes more frequent or increasingly severe.
• It is remarkable that homogenisation has gone-on for as long as it has. Changing data to agree with models is unscientific. For all its complexity the process is faulty and should be discontinued.

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