- JoNova - https://joannenova.com.au -

Sydney Observatory where warming is created by site moves, buildings, freeways

The iconic Sydney Observatory is Australia’s longest running weather station. But everything around the site has changed. Bill Johnston has spent months researching, photographing, and hunting through historic files to document those changes. He wasn’t paid for this work, but what he found was that the BOM has missed that the area around the thermometers has changed dramatically over the last century, so much so, that he claims it’s scientifically meaningless to try to construct climate trends from this data. Aerial photographs show exposure of the instruments changed in 1950, when Stevenson screens were moved, and after a brick wall was built metres from the screen in about 1972. It is suspicious that the changes are undocumented in Bureau reports, especially given they are responsible for much of the “unprecedented warming” in Sydney’s temperature data.  The BOM may counter that this site is not used to calculate warming trends across Australia, but as Bill points out, Sydney Observatory is used to homogenize other sites that are. So site changes and the urban heat island effect infects many country sites, and the traffic in Sydney “warms the nation”.  — Jo


Its fake news week!

Guest post by Dr. Bill Johnston[1].

While reporters are at the beach watching sea levels rise; Prime Ministers are having drinkies with mates in their harbourside mansions, while organizing group-hugs over the NBN for those at Hazelwood and Portland destined to loose their jobs in the new-year; and professors are off on jaunts and junkets; hardly any one is left looking-out for fake climate-news.

Sydneysiders are told incessantly they are experiencing a scorcher: “sizzling end to city’s hottest year on record” says Fairfax’s Peter Hannam; backed-up by Fairfax’s own Weatherzone meteorologist Joel Pippard who pipped-up that “without a doubt” the late December heat means Sydney would notch the city’s hottest year in records going back to 1858 … and already on the ABC, the Bureau reported it will be Australia’s fifth warmest year since 1910 ….

The trouble is, its bunkum – the climate-club is making it up as they go along!

Sydney Observatory data are affected by four influential site changes:

It is astonishing that the Bureau and all the professors, failed to correct for the move in 1949; and construction of the wall, probably in 1972. Together with opening of the Cahill Expressway, and replacing the large screen with a small one, changes modified the environment and created trends that have nothing to do with the climate.

Although Observatory data are used to create fake-news about Sydney’s climate, they are not used to calculate Australia’s warming. Nevertheless, despite that data are faulty, they homogenise ACORN sites at Cobar, Walgett, Gunnedah, Williamtown RAAF, Bathurst, Richmond RAAF, Nowra RAN and Moruya Heads Pilot Station. Those sites homogenise others: Moruya Heads Pilot Station is used for Sydney Observatory, Bathurst, Canberra and Dubbo; Williamtown RAAF for Coffs Harbour, Port Macquarie, Scone, Bathurst, Sydney Observatory and Moruya Heads Pilot Station; Canberra for Dubbo, Nowra, Moruya Heads Pilot Station and Bathurst; Gunnedah, for Moree, Inverell, Dubbo and Bourke; Dubbo is used for Tibooburra and so-on. Few ACORN datasets are independent and it’s easy to see how faults in Sydney data get propagated across the network by the homogenisation process. Homogenised ACORN data with their embedded faults are used to calculate Australia’s warming.

The details are below.


Fake temperature records at Sydney Observatory

For the last two decades Australia’s Bureau of Meteorology has engaged in a fake-news campaign to convince Australians that average temperatures are rising; extreme temperatures are more frequent, and that trends in extremes are increasing. Tracking back through standalone reports, low and mid -level scientific papers, published for example in the Australian Meteorological Magazine and the various publications of the Australian Meteorological and Oceanographic Society (AMOS) (the AMOS Bulletin and the Australian Meteorological and Oceanographic Journal (now the Journal of Southern Hemisphere Earth Systems Science)); as well as top-shelf journals; a handful of people, some at the University of NSW, Melbourne University, ANU and Monash, are stand out weather-fakers. The campaign is championed by the Bureau; whose many reports and opportunistic press releases are designed to stir alarm.

Much of what is claimed about the weather is based on inadequate analysis, data-picking and purposeful data manipulation in the name of homogenisation. Sydney Observatory is used here as an example.

Since Melbourne’s La Trobe Street site closed in January 2015, Sydney Observatory (66062) is Australia’s longest same-site weather station. Its temperature series is one of the longest in the southern hemisphere and data have been analysed, used or reported-on in publications by Australian and overseas authors; commentators; bloggists; climate-alarmist professors; The Conversation; Weatherzone and the press generally. According to the ACORN catalogue (Australian Climate Observations Reference Network – Surface Air Temperature (ACORN-SAT)):

Sydney (066062)

The current site is located on Observatory Hill, in a small, grassed enclosure (about 10 by 10 m) about 100 m south of the main Sydney Observatory complex. There is a freeway immediately east of the site but it is in a deep cutting at this point.


Originally the site was in the main Observatory grounds. It moved about 100 m south to its current location in 1917. The earlier site was a more exposed location on a hilltop and had lower maximum and higher minimum temperatures than the current location. An automatic weather station was installed at the current site on 8 August 1990. The area is heavily built-up and has been since at least the late 19th century. An analysis of minimum temperature trends in the ACORNSAT data showed no evidence of an abnormal warming trend relative to non-urban sites in the region, indicating that any urban influence on the data was already fully developed by the time ACORN-SAT begins in 1910.

Little of the ACORN narrative is true.

At the previous observatory site, thermometers moved from a Glaisher stand to an airy thermometer house beside a rose garden in front of the west-wing of the Observatory in 1865 (Figure 1). Nighttime exposure changed and minimum temperature (Tmin) stepped-up. The garden is gone; however, the structure, which fell into decay is re-built in the same place. Although the thermometer house may have been used until 1916, a large standard Stevenson screen was operating before 1911 (Figure 1). An up-step in maximum temperature (Tmax) in 1908 is consistent with Tmax being measured in the screen from 1907.

That move from the thermometer house to the enclosed screen resulted in a Tmax up-step of 0.64oC, which was not due to “urban influence” or the climate. In contrast to Tmax, average Tmin remained the same after instruments were rehoused (i.e. nighttime exposure was not significantly affected). The move to another standard screen 100 m south at the cottage in 1917 had no impact on temperature. However, data are transiently disturbed from 1921 to about 1930 during construction of the Sydney Harbour Bridge, which opened in 1932; and possibly building of the Weather Bureau office, which opened in 1922 (Figure 2).

The Cahill Expressway ‘circular road’ was laid out in 1938 and by 1940 construction is well advanced (Figure 2).  As part of that work, most of the Fort Street School, then south of the cottage was demolished and replaced by a new school built north of the cottage, which opened in 1942. (Photographs in the City of Sydney Archives show the laneway being sealed in about 1940 and the Cahill Expressway under construction.)

Sydney Observatory, Historical photo. Thermometer, Urban Heath Island Effec t

Figure 1. The meteorological lawn said to be in 1864 but possibly later (a); and (b) with a Stevenson screen in 1911. Transpiration by vegetation in (a) is absent in (b), which may affect measurements. (Photos courtesy NSW State Library.)

Sydney Observatory, Historical photo. Thermometer, Urban Heath Island Effect, Bureau of Meteorology.

Figure 2. The building 100 m south of the Observatory occupied by the Weather Bureau in 1922 viewed from the north on 25th June 1932 (a). The upper level appears lived-in. The historic messenger’s cottage is on the left; another house is east of the cottage and behind (south) is the Fort Street School. The open foreground is grassy parkland and the path still leads to Kent Street via the Agar Steps.  (http://nla.gov.au/nla.obj-157852963 (accessed 24th April 2016; from a damaged glass-plate negative.) The building is surrounded by hoarding during construction of the Cahill Expressway (b). The photo is taken across where the new school opened in 1942 (City of Sydney Archives).

Sydney 1943 imaginary accessed on 15th December 2012 (http://maps.six.nsw.gov.au) shows two Stevenson screens at the end of a short concrete path adjacent to the lane in the northeast corner of the cottage yard (Figure 3). The area bounded by the open-cut (about 1.5 ha in total) is isolated from its surroundings. Stevenson screens would be shaded in the afternoon by the fig tree 15 m away across the laneway (which survived from before 1935), the new school building and from the west by the imposing Weather Bureau building, making it not an ideal site for weather observations.

Sydney Observatory, Historical photo. Thermometer, Urban Heath Island Effect

Figure 3. The open-cut up-ramp for the Cahill Expressway laid out in 1938 (a) is well advanced by 1940 (b).


An aerial photograph in December 1949 (Figure 4) shows work associated with the Cahill Expressway is progressing and the Bradfield Highway being widened to accommodate an additional six tollgates (http://www.photosau.com.au/cosmaps/scripts/display Index.asp?Index=AO1). By then, hoarding is gone and the school building south of the cottage is demolished. Serviced by a concrete path, which was not there in 1943, Stevenson screens are relocated to the opposite (southeast) corner of the cottage yard. (An earlier 1947 photo (not shown here) shows the Stevenson screen with the school and laneway close in the background. Thus screens were moved after 1947 and before December 1949.

Sydney Observatory, Historical photo. Thermometer, Urban Heath Island Effect

Figure 4. An aerial-mosaic (http://maps.six.nsw.gov.au) of the Observatory weather station in 1943 shows the new school (A), the Weather Bureau building (B), the historic messengers cottage (C), two Stevenson screens in the northeast corner of the cottage yard at the end of a concrete path (D); hoarding isolates the work site (E) (note the access gate in Upper Fort Street); an old school building remains to be demolished (F).


The number of traffic lanes on the Harbour Bridge increased from four to six in 1950 and south of the cottage, a new school gymnasium opened in 1952. An oblique view in 1966 (Figure 5) shows the site is open to the south and that traffic passes about 35 m east of the relocated Stevenson screens.

Sydney Observatory, Historic Aerial Photo. Cahill Expressway constuction. Aerial photo. Thermometer, Climate Change, Station siting.

Figure 5. In 1949, A, is the former site at the Observatory; B, the new Fort Street Public School; C, the Weather Bureau building; D, is two Stevenson screens in the southeast corner of the cottage yard; E, the tunnel under the Bradfield Highway linking to the Cahill Expressway, and F, road widening for new tollgates commissioned in 1950. No brick wall or hoarding is evident along the southern boundary of the meteorological enclosure.


The laneway between the school and the cottage is an east-west breezeway. In the afternoon, westerly wind picks-up heat from often stalled traffic emerging from the tunnel under the Bradfield Highway and on the up-ramp; easterly sea breeze, picks-up heat from traffic on the approach to the Harbour Bridge tollgates. Tmin, which occurs under still-air conditions around dawn, is influenced mainly by nighttime emitted radiation and cool-air descending from up-slope. The screen was moved away from that influence in 1949, consequently there is an up-step in Tmin in 1950. Heat stored by buildings, concrete and bitumen; and traffic cause temperatures during the day to increase immediately the Cahill Expressway opens in 1957.

In 1970, there are still two Stevenson screens in the southeast corner of the cottage yard serviced by a concrete path, which originates from the end of the original path (Figure 6). Shadows are cast southwards; however, there is no indication of a wall between the screens and the school gymnasium. A traffic lane joining with Kent Street is cropped-off the photograph and no works associated with development of the first stage of the Western Distributor, which opened in 1972 are visible. In 1975, there is a brick wall between the meteorological enclosure and the school gymnasium (Figure 7). Later, a single large screen replaced the two that are there in 1975.

Cahill expressway tolls. Sydney.

Figure 6. Two Stevenson screens are visible in the southeast corner of the cottage yard in 1966 (A); no brick wall separates the enclosure from the school gymnasium (B), which opened in 1952. The Weather Bureau building (C) casts shadow over the meteorological enclosure; (D) is the Fort Street Public School. (Portion of “View from IBM; Max Dupain and Associates 1966”. State Library of NSW, Mitchell Library, courtesy of Hely, Bell & Horne.) The Observatory is in the background (E). Traffic is bank-up to pay tolls.


Sydney Observatory, Historical photo. Thermometer, Urban Heath Island Effect

Figure 7. A grainy 1970 aerial photograph (NSW Spatial Services) shows the concrete path and two Stevenson screens in the south-east corner of the cottage yard (A); lack of shadow confirms there is no brick wall enclosing the southern boundary of the site (B). The full image shows no connection with the Western Distributor, which opened to Day Street (west of Sydney Town Hall) in 1972. However, there is direct access to the Harbour Bridge from Kent Street (C), which is below the ridge on the left. (Whilst they are still there, northbound tollgates may not be operating – one-way tolling (north to south) is introduced in 1970.)


The next major change is installation of an automatic weather station (AWS) in situ on 8th August 1990 and replacement of the large screen with a small one on 20th January 2000. Manual observations apparently ceased when the AWS is installed. By  2016 the site appears settled (Figure 8), which belies its history. Close-up inspection of the wall shows some segments are re-pointed, probably because, due to lack of dampcourse, mortar has deteriorated. Stevenson screens open to the south and the “T” at the end of the concrete path is the location of the two previous screens with the path in between, whose northern louvers would have faced the camera.

Photo Sydney Observatory, Bureau of Meteorology, Climate Change. Thermometer siting.

Figure 8. A brick wall separates the meteorological enclosure from the school gymnasium in 1975 (A). The Kent Street connection with the Bridge is cut-off; new lanes connect with the first (Day Street) stage of the Western Distributor (B); further work is progressing, which eventually links to Kent and Clarence Streets (C). Close examination shows the two Stevenson screens are possibly moved (relative to the footpath), probably during construction of the wall. Shade cast south by the Weather Bureau building, indicates the photo is taken in winter. It is also not a busy-traffic day. (Note that the roadway is further widened to accommodate breakdown recovery vehicles (D).)

Bureau of Meteorology, Sydney, Observatory Hill, thermometer siting.

Figure 9. By 2016 in (a) the brick wall is weathered; the “T” at the end of the path is the former location of two large Stevenson screens; their single large replacement is superceeded in 2000 by the small one housing AWS sensors. In (b), the screen is confined by the cottage, the now derelict Weather Bureau building, school and Environmental Education Centre. A bitumen car park is beyond the wall and to the south is the city. (The historic messenger’s cottage is now refurbished as the school office.)


Effect of site/instrument changes on temperature

Step-changes in average Tmax and Tmin are aligned with known site changes in Figure 9. The sequential t-test used to detect step-changes is a whole-of-dataset procedure (i.e. it is not done piecewise) that detects (rejects) shifts in the mean with the same target probability level. It is applied iteratively to isolate permanent step-changes from those due to weather-changes caused by ElNiño cycling. The test is parametric, objective and P-levels are adjusted for autocorrelation. Importantly, changepoints can’t be specified in advance; so detected shifts are interpreted after analysis is complete.

Each step-change defines a data-segment whose regime-mean is different to adjacent segments (Figure 9). If an abrupt change in ambience occurs (for example, exposure of the screen changes), the effect is additive to day-to-day temperature variation. T shifts up (down) depending on if the effect is to increase (reduce) heat-load on the instruments; or something else happens such as if a screen is replaced or thermometer develops a constant off-set (a bubble in its mercury/alcohol column, for instance). (A range of statistical tests can be used to detect time-wise step-changes (and changes in the variability of data). Different methods applied to the same data mostly identify the same step-changes.)

To recap: Temperature time-series consist of two signals. Day-to-day temperature is measured relative to background ambience, which is the dataset average. Disturbances that permanently alter that baseline: for Tmax, moving instruments to the Stevenson screen in 1908; opening of the Cahill Expressway in 1958 and moving instruments to a small Stevenson screen in 2000 caused permanent up-steps in the data that had nothing to do with the climate. The minimum temperature baseline changed when the instruments moved from a Glaisher stand to the thermometer house in 1876; screens were moved away from the breeze-way in the north-eastern corner of the cottage yard to the south-eastern corner, probably in 1949; the wall is built nearby around 1972; and the screen size changed in 2000.


Graph, temperature changes Sydney, Urban Heat Island Effect, station siting.

Figure 9. Changes in the vicinity of the Sydney Observatory weather station and step-changes in Tmax and Tmin. Since records commenced in 1859, step-changes caused by site changes have caused 2.09oC of warming in Tmax data, which has nothing to do with the climate. Step-changes in Tmin have added 2.05oC of warming to the data.


[1] Former NSW natural resources research scientist. Bill is currently auditing many of the Bureau’s weather stations.

9.8 out of 10 based on 92 ratings