Evidence for a strong urbanization signal; 0.3 degrees C per decade in Canberra Airport temperature data 1997-2009January 12th, 2010 by Warwick Hughes
Canberra/Queanbeyan is a sprawling collection of suburbs population 300,000 plus – which extends over 30km north south and nearly 20km east west. Canberra was selected as the Australian Federal Capital early last century and urbanisation would have started after the “old” Parliament House started operating in the late 1920′s. The post WWII boom in Australia plus increasing migration accelerated the addition of new suburbs to Canberra, a process which continues to this day.
There are monthly maximum and minimum temperature data from the Airport starting March 1939 running complete to the present time. During 1996 the ACT Govt in conjunction with the BoM (Bureau of Meteorology) installed an air-monitoring station at Tuggeranong in Canberra southern suburbs where there are air quality issues.
As part of this instrumentation, temperature is recorded and the BoM publishes monthly mean max and mean min at this website, look for Site name: TUGGERANONG (ISABELLA PLAINS) AWS Site number: 70339 and you can download the data for yourself. Canberra Airport data is Site name: CANBERRA AIRPORT Site number: 70014, and I understand the BoM instruments are on the Fairbairn RAAF Base side of the airport, that is several hundred metres across the runways, NE of the main passenger terminal . See GoogleEarth map thanks to MartinH of Canberra
The difference between Canberra Airport and Tuggeranong is 0.3 degrees C per decade – a very significant indication of urban effects in the Canberra data. Remember too that the Tuggeranong data will have some UHI contamination too, so the true UHI at Canberra Airport could be in excess of 0.3 degrees C per decade.
This site shows how even small urban areas can be significantly affected by the UHI effect.
Canberra Airport is included in the BoM Reference Climate Station Network – which are claimed to be high quality sites and as free as possible from non-climatic influences.
The ACT Govt has a Dept of Environment and a Commissioner for the Environment who every few years produces a “State of the Environment” report. I noticed in her 2007 report an interesting comment to the effect that the Canberra Airport temperature data could be affected by nearby construction.
For a Govt bureaucrat to raise such an issue counter to IPCC dogma – and “in public”, I found noteworthy. Anyway, this lead to a report from an ex BoM meteorologist at the Australian National University, The Fenner School of Environment and Society.
An update: “Clarification and context” statement was added to the Commissioners 2007 web report apparently by the BoM and Fenner – all copied below. You can read the pdf report, “Has Development around Canberra Airport affected its use as a Climate Reference Station?”.
I note that the author in the first paragraph describes the issue as stemming from the recent (2006) construction – and that the site has been relatively unchanged up to 2005. The report has a map showing the Airport and the Tuggeranong station “..about 15km to the SW..”, there are photos of the Airport site and some tables of statistics which I have to confess I am leaving for somebody else to comment on. This is because I was interested in the wider issue of urban warming in the Canberra Airport data – not just the issue of a possible change at 2005-2006.
This site describes the Melbourne urban heat island (UHI) and this illustration from a BoM report shows the extent to which urban areas can be warmer than their more rural surroundings, on say a night that is not very windy. I think these data were gathered by a Melbourne University team taking temperature sensors across Melbourne on a motor cycle some decades ago. This sort of mobile experiment could be carried out in Canberra if somebody had the tech skills to link a temperature sensor mounted on a vehicle to a laptop running data logging software – should be possible to incorporate GPS positioning and produce temperature profiles along driven traverses.
IMHO the urban contamination in Canberra Airport data is likely to arise for the following reasons.
 A steady increase in buildings, tarmac, energy use and activity at the airport over the decades – particularly post WWII.
 A steady increase in buildings, tarmac, energy use and activity over the decades – particularly post WWII, at suburbs within 5km of the instruments. These localities are (a) the nearby industrial suburb of Fyshwick 3 km SW. (b) The NSW City of Queanbeyan commences 5km SSE of Fairbairn. (c) Duntroon Military College is 3km west. (d) The Canberra CBD, termed Civic, is only 6.5km WNW of Fairbairn. (e) The Parliamentary suburbs are about 7km westerly from Fairbairn.
 A steady increase in buildings, tarmac, energy use and activity over the decades – particularly post WWII, at suburbs further away that form a large north south belt extending ~10km northerly, 13km north-westerly and 20km southerly, from Civic, see map for all these places. The black O on the map marks the approx location of the BoM weather station. Note that the grid squares on my map are 1km.
A north-south range of peaks lies west of the airport which would tend to channel air movements but we must remember that Australian heat-wave and dust storm affected air not infrequently makes its way for over 2400km across the Tasman Sea to register a signal in New Zealand weather data. So the concept of urban warmed air from a range of localities peripheral to Fairbairn being wafted to affect the BoM instruments, is hardly a radical one.
Text below copied from ACT Dept of Environment website linked above.
Measuring weather patterns in the ACT has traditionally been undertaken at the weather station at the Canberra International Airport. The expansion of the airport has affected the accuracy of measurements at the weather station. Carparks have now been built around the weather station significantly changing the micro-climate of the measurement area. This means that the data collected now cannot be effectively compared to previous data. This will affect the measurement of climate and weather trends in the ACT. With climate change and future weather changes becoming a significant issue, high quality long-term records are crucial for effective future planning and management. It is important that a new weather station in the ACT is established, with data adequately correlated with previous data from the airport weather station.
Update: Clarification and context for statement about the weather station at Canberra Airport
This update provides clarification and context for material in paragraph 4 of this page, that starts “Measuring weather” and concludes “…correlated with previous data from the airport weather station.” The information is provided by Associate Professor Janette Lindsay, Mr Clem Davis and Mr Stephen Lellyett (Bureau of Meteorology) 26 August 2008
Measuring weather and climate conditions in vicinity of Canberra in the ACT has been undertaken at the weather station at the Canberra International Airport, one of a limited set of designated Climate Reference Stations in Australia, since 1939. Based on limited data it appears that the expansion of built infrastructure at the airport has affected measurements at the weather station for temperatures and sunshine hours, and possibly for evaporation and humidity. Carparks have recently been built adjacent to the weather station significantly changing the micro-climate of the measurement area for maximum and minimum temperatures in some months. A multi-story building constructed east of the weather station now shades the sunshine recorder shortly after sunrise. This means that data collected since these developments potentially cannot be reliably compared to the previous long-term record at this site. This would affect the long-term record and ongoing monitoring of climate and weather trends in the ACT. With climate change and future weather changes becoming a significant issue, high quality long-term records are crucial for effective future planning and management.
Hence, it is important that a new weather station with long term tenure be established at an appropriate location in the ACT as soon as possible, with a sufficiently long overlap period of concurrent measurements to establish a robust statistical relationship between the two sites through adequate correlation of new and previous data from the existing airport weather station. To that end, the Bureau of Meteorology and Canberra International Airport have been actively working together to identify a site which would satisfy the requirements of a Climate Reference Station, aerodrome meteorological requirements, long term airport development plan, environmental protection, and property lease requirements. The new comparison site is expected to be operational by the end of September 2008.