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ACORN 2.1 influence on Northern Territory temperature trends

Australia New South Wales Queensland South Australia Tasmania Victoria Western Australia


In October 2020 the Bureau of Meteorology again rewrote Australia's temperature history with the release of ACORN 2.1, an update to its homogenised ACORN 2 dataset (Australian Climate Observations Reference Network - Surface Air Temperatures) released in late 2018 that significantly increased the rate of climate warming since 1910.

There are five ACORN stations in the Northern Territory. This page analyses the daily temperatures at all five weather stations and averages the three with a start year of 1910 to ensure a uniform timescale. The other two excluded stations have temperature recordings starting in years after 1910, the most recent being Rabbit Flat with a start year of 1970.

The three long-term weather stations analysed on this page (with a start year of 1910) had a 1910-1964 average maximum of 30.02C in ACORN 2 and a 1910-1964 average maximum of 30.05C in ACORN 2.1 - a 0.03C warming of historic maxima.

The three long-term weather stations had a 1910-1964 average minimum of 17.93C in ACORN 2 and a 1910-1964 average minimum of 18.03C in ACORN 2.1 - a 0.10C warming of historic minima.

Daily temperatures in ACORN 2.1 and RAW have been annualised, and below are charts showing the difference between the ACORN 2.1 homogenised dataset when compared to original raw annual temperatures. This analysis only allows the inclusion of years within which there were no months with less than 15 days of recorded temperatures, as is the ACORN protocol.

Three Northern Territory stations begin in 1910 and end in 2019 in ACORN 2.1 and RAW - Alice Springs, Darwin and Tennant Creek. The first charts below show maximum and minimum temperature trends at these three stations with associated data.

Excel files at the bottom of each station chart and data summary can be downloaded to compare how the ACORN 2.1 algorithms influence daily, monthly and annual temperatures at all five sites since 1910.

acorn 2.1 northern territory maximum temperatures

1910-1964 - ACORN 2.1 30.05C / raw 30.83C

1965-2019 - ACORN 2.1 31.07C / raw 31.09C

ACORN 2.1 warmed 1.02C / raw warmed 0.26C

Average change per decade : ACORN 2.1 0.21C / raw 0.08C

Northern Territory 2000-2019 - ACORN 2.1 31.42C / raw 31.41C

The first decade, 1910-1919, averaged 29.60C in ACORN 2.1 and 30.84C in raw

The final decade, 2010-2019, averaged 31.56C in ACORN 2.1 and 31.56C in raw

1961-90 - ACORN 2.1 - 30.72C / raw 30.82C

Download Excel spreadsheet for three NT weather stations in ACORN 1, ACORN 2.1 and RAW

acorn 2.1 northern territory minimum temperatures

1910-1964 - ACORN 2.1 18.03C / raw 18.43C

1965-2019 - ACORN 2.1 18.52C / raw 18.75C

ACORN 2.1 warmed 0.49C / raw warmed 0.32C

Average change per decade : ACORN 2.1 0.09C / raw 0.03C

Northern Territory 2000-2019 - ACORN 2.1 18.71C / raw 18.77C

The first decade, 1910-1919, averaged 17.90C in ACORN 2.1 and 18.45C in raw

The final decade, 2010-2019, averaged 18.80C in ACORN 2.1 and 18.78C in raw

1961-90 - ACORN 2.1 - 18.24C / raw 18.61C

Download Excel spreadsheet for three NT weather stations in ACORN 1 and ACORN 2.1 and RAW

Station menu

Alice Springs, Darwin, Rabbit Flat, Tennant Creek, Victoria River Downs

Alice Springs

acorn 2 alice springs maximum temperatures

1910-1964 - ACORN 2.1 28.11C / raw 28.29C

1965-2019 - ACORN 2.1 29.31C / raw 29.07C

ACORN 2.1 warmed 1.20C / raw warmed 0.78C

Average change per decade : ACORN 2.1 0.22C / raw 0.11C

Alice Springs 2000-2019 - ACORN 2.1 29.60C / raw 29.60C

1961-90 - ACORN 2.1 28.98C / raw 28.59C

Pre 1972 .0 F rounding ACORN 2.1 - 16.98% / raw - 50.52%

Post 1972 .0 C rounding ACORN 2.1 - 10.06% / raw - 11.32%

The first decade, 1910-1919, averaged 27.45C in ACORN 2.1 and 28.52C in raw

The final decade, 2010-2019, averaged 29.65C in ACORN 2.1 and 29.65C in raw

Alice Springs 15540 has annual max temps back to 1879: 1879-1889 + 1891 +1893-1909 = 28.85C

15540 overlap with 15590 1 November 1941 to 31 December 1953 : 15540 28.51C / 15590 28.13C

ACORN catalogue: The original site (015540) was at the Telegraph Station, 3 km north of the town. There is no known documentation of the screen type at the Telegraph Station but the observations are consistent with a Stevenson screen having been used there. The site was enclosed by a rock wall about 1 m high and painted white that would have interrupted wind flow and reflected heat. Observations moved to the Post Office on 23 January 1932. The Post Office site continued until 1953 but data after 1944 were not used in ACORN-SAT as there appear to have been changes at the Post Office site around the time that the airport site opened. Measurements have been taken at the airport (015590) since 1941. There was a site move (550 m east-northeast) in July 1974. An automatic weather station was installed on 21 March 1991 and became the primary instrument on 1 November 1996. The site moved a few metres west on 27 May 2002.

1986-1995 raw max averaged 28.95C and post AWS 1997-2006 averaged 29.48C

Alice Springs max Excel spreadsheets

acorn 2 alice springs minimum temperatures

1910-1964 ACORN 2.1 11.90C / raw 13.11C

1965-2019 ACORN 2.1 12.40C / raw 13.21C

ACORN 2.1 warmed 0.50C / raw warmed 0.10C

Average change per decade : ACORN 2.1 0.10C / raw -0.02C

Alice Springs 2000-2019 - ACORN 2.1 12.93C / raw 13.21C

1961-90 - ACORN 2.1 11.86C / raw 13.10C

Pre 1972 .0 F rounding ACORN 2.1 - 17.73% / raw - 55.40%

Post 1972 .0 C rounding ACORN 2.1 - 9.78% / raw - 11.49%

The first decade, 1910-1919, averaged 12.13C in ACORN 2.1 and 13.32C in raw

The final decade, 2010-2019, averaged 13.11C in ACORN 2.1 and 13.11C in raw

Alice Springs 15540 has annual min temps back to 1879: 1879-1902 + 1904-1909 = 12.83C

15540 overlap with 15590 1 November 1941 to 31 December 1953 : 15540 12.46C / 15590 12.86C

1986-1995 raw min averaged 13.68C and post AWS 1997-2006 averaged 13.24C

Alice Springs min Excel spreadsheets

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Darwin

acorn 2 darwin maximum temperatures

1910-1964 - ACORN 2.1 31.04C / raw 32.10C

1965-2019 - ACORN 2.1 32.12C / raw 32.22C

ACORN 2.1 warmed 1.08C / raw warmed 0.12C

Average change per decade : ACORN 2.1 0.18C / raw 0.03C

Darwin 2000-2019 - ACORN 2.1 32.47C / raw 32.47C

1961-90 - ACORN 2.1 31.74C / raw 32.02C

Pre 1972 .0 F rounding ACORN 2.1 - 18.07% / raw - 32.61%

Post 1972 .0 C rounding ACORN 2.1 - 9.72% / raw - 11.32%

The first decade, 1910-1919, averaged 30.83C in ACORN 2.1 and 32.38C in raw

The final decade, 2010-2019, averaged 32.63C in ACORN 2.1 and 32.63C in raw

Darwin 14016 has annual max temps back to 1885: 1885-1909 = 32.97C

14016 overlap with 14015 1 February 1941 to 31 January 1942 : 14016 31.42C / 14015 30.85C

ACORN catalogue: Earlier observations were made at the Post Office (014016), in the central city area. This is on a peninsula in Darwin Harbour which means that the prevailing dry-season southeasterlies have a trajectory over Darwin Harbour (whereas at the airport they are over land). The site deteriorated progressively from the mid-1930s, becoming overshadowed by trees, especially after 1937. The site (along with the remainder of the Post Office) was destroyed in the Japanese air raids of February 1942 and never rebuilt. The airport site (014015) has been operating since February 1941. An automatic weather station was installed on 1 October 1990 and became the primary instrument on 1 November 1996. The site moved about 900 m east (along the southern edge of the airport) on 7 August 2001, with observations at the original site continuing under the station number 014040 until June 2007.

1986-1995 raw max averaged 32.11C and post AWS 1997-2006 averaged 32.24C

Darwin max Excel spreadsheets

acorn 2 darwin minimum temperatures

1910-1964 - ACORN 2.1 22.69C / raw 23.39C

1965-2019 - ACORN 2.1 23.18C / raw 23.28C

ACORN 2.1 warmed 0.49C / raw cooled 0.11C

Average change per decade : ACORN 2.1 0.07C / raw -0.03C

Darwin 2000-2019 - ACORN 2.1 23.18C / raw 23.18C

1961-90 - ACORN 2.1 23.07C / raw 23.29C

Pre 1972 .0 F rounding ACORN 2.1 - 16.47% / raw - 33.85%

Post 1972 .0 C rounding ACORN 2.1 - 9.24% / raw - 11.93%

The first decade, 1910-1919, averaged 22.59C in ACORN 2.1 and 23.62C in raw

The final decade, 2010-2019, averaged 23.27C in ACORN 2.1 and 23.27C in raw

Darwin 14016 has annual min temps back to 1885: 1885-1909 = 23.56C

14016 overlap with 14015 1 February 1941 to 31 January 1942 : 14016 24.20C / 14015 22.67C

1986-1995 raw min averaged 23.60C and post AWS 1997-2006 averaged 23.13C

Darwin min Excel spreadsheets

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Rabbit Flat

acorn 2.1 rabbit flat maximum temperatures

1970-1994 - ACORN 2.1 33.79C / raw 33.46C

1995-2019 - ACORN 2.1 34.00C / raw 34.02C

ACORN 2.1 warmed 0.21C / raw warmed 0.56C

Average change per decade : ACORN 2.1 0.15C / raw 0.31C

Rabbit Flat 2000-2019 - ACORN 2.1 33.98C / raw 33.98C

Pre 1972 .0 F rounding ACORN 2.1 - 17.93% / raw - 22.42%

Post 1972 .0 C rounding ACORN 2.1 - 10.37% / raw - 12.73%

The first decade, 1970-1979, averaged 33.50C in ACORN 2.1 and 32.87C in raw

The final decade, 2010-2019, averaged 34.10C in ACORN 2.1 and 34.10C in raw

15548 overlap with 15666 15 November 1996 to 30 November 1998 : 15548 34.42C / 15666 34.10C

ACORN catalogue: The first site (015548) has no indication of any moves between 1969 and 1998 but did become rather overgrown over time. The automatic weather station was installed about 200 m to the west in 1996. The two sites operated in parallel from 1996 to 1998. There is no indication of any moves at the new site.

Assuming the AWS was operational from 1996, 1986-1995 raw max averaged 34.13C and post AWS 1997-2006 averaged 33.71C

Rabbit Flat max Excel spreadsheets

acorn 2.1 rabbit flat minimum temperatures

1970-1994 - ACORN 2.1 16.74C / raw 16.33C

1995-2019 - ACORN 2.1 16.73C / raw 16.64C

ACORN 2.1 cooled 0.01C / raw warmed 0.31C

Average change per decade : ACORN 2.1 0.17C / raw 0.09C

Rabbit Flat 2000-2019 - ACORN 2.1 16.55C / raw 16.55C

Pre 1972 .0 F rounding ACORN 2.1 - 19.03% / raw - 33.01%

Post 1972 .0 C rounding ACORN 2.1 - 10.49% / raw - 14.88%

The first decade, 1970-1979, averaged 15.94C in ACORN 2.1 and 16.25C in raw

The final decade, 2010-2019, averaged 16.62C in ACORN 2.1 and 16.62C in raw

15548 overlap with 15666 15 November 1996 to 30 November 1998 : 15548 17.47C / 15666 17.89C

Assuming the AWS was operational from 1996, 1986-1995 raw min averaged 16.37C and post AWS 1997-2006 averaged 16.72C

Rabbit Flat min Excel spreadsheets

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Tennant Creek

acorn 2 tennant creek maximum temperatures

1910-1964 - ACORN 2.1 31.01C / raw 32.18C

1965-2019 - ACORN 2.1 31.79C / raw 31.98C

ACORN 2.1 warmed 0.78C / raw cooled 0.20C

Average change per decade : ACORN 2.1 0.19C / raw 0.07C

Tennant Creek 2000-2019 - ACORN 2.1 32.20C / raw 32.16C

1961-90 - ACORN 2.1 31.46C / raw 31.87C

Pre 1972 .0 F rounding ACORN 2.1 - 19.33% / raw - 61.79%

Post 1972 .0 C rounding ACORN 2.1 - 9.12% / raw - 11.84%

The first decade, 1910-1919, averaged 30.60C in ACORN 2.1 and 31.73C in raw

The final decade, 2010-2019, averaged 32.41C in ACORN 2.1 and 32.40C in raw

15087 overlap with 15135 27 July 1969 to 31 October 1970 : 15087 32.36C / 15135 32.04C

ACORN catalogue: The original site (015087) was based in the town. There was a major move (12 km south) in June 1935 and a smaller move of about 20 m in November 1963. This later site was quite close to a road. New screens were installed to replace damaged ones in May 1945 and November 1958. Observations ceased in 1970. This airport site has been operating since 1969. An automatic weather station was installed on 8 July 1990 and has been the primary instrument since 1 November 1996. There are no known substantial moves at this location.

1986-1995 raw max averaged 32.27C and post AWS 1997-2006 averaged 31.81C

Tennant Creek max Excel spreadsheets

acorn 2 tennant creek minimum temperatures

1910-1964 - ACORN 2.1 19.44C / raw 18.74C

1965-2019 - ACORN 2.1 19.96C / raw 19.75C

ACORN 2.1 warmed 0.52C / raw warmed 1.01C

Average change per decade : ACORN 2.1 0.09C / raw 0.14C

Tennant Creek 2000-2019 - ACORN 2.1 20.03C / raw 19.92C

1961-90 - ACORN 2.1 19.76C / raw 19.42C

Pre 1972 .0 F rounding ACORN 2.1 - 17.61% / raw - 64.64%

Post 1972 .0 C rounding ACORN 2.1 - 9.63% / raw - 11.87%

The first decade, 1910-1919, averaged 19.08C in ACORN 2.1 and 18.52C in raw

The final decade, 2010-2019, averaged 20.01C in ACORN 2.1 and 19.96C in raw

15087 overlap with 15135 25 July 1969 to 31 October 1970 : 15087 18.56C / 15135 18.91C

1986-1995 raw min averaged 20.43C and post AWS 1997-2006 averaged 19.90C

Tennant Creek min Excel spreadsheets

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Victoria River Downs

acorn 2.1 rabbit flat maximum temperatures

1965-1991 - ACORN 2.1 35.07C / raw 34.56C

1992-2019 - ACORN 2.1 34.95C / raw 34.55C

ACORN 2.1 cooled 0.12C / raw cooled 0.1C

Average change per decade : ACORN 2.1 0.05C / raw 0.08C

Victoria River Downs 2000-2019 - ACORN 2.1 34.90C / raw 34.64C

Pre 1972 .0 F rounding ACORN 2.1 - 21.65% / raw - 40.40%

Post 1972 .0 C rounding ACORN 2.1 - 10.81% / raw - 18.87%

The first decade, 1965-1974, averaged 34.91C in ACORN 2.1 and 34.76C in raw

The final decade, 2010-2019, averaged 35.12C in ACORN 2.1 and 35.12C in raw

ACORN catalogue: The site moved 250 m northwest in August 1987. An automatic weather station was installed on 9 May 1997. Station photos indicate that the grass was watered up until around 2007; data indicate a marked increase in maximum temperatures around this time, especially during the dry season.

1987-1996 raw max averaged 34.62C and post AWS 1998-2007 averaged 34.07C

Victoria River Downs max Excel spreadsheets

acorn 2.1 rabbit flat minimum temperatures

1965-1991 - ACORN 2.1 19.99C / raw 19.83C

1992-2019 - ACORN 2.1 19.61C / raw 19.44C

ACORN 2.1 cooled 0.38C / raw cooled 0.39C

Average change per decade : ACORN 2.1 0.03C / raw 0.01C

Victoria River Downs 2000-2019 - ACORN 2.1 19.38C / raw 19.38C

Pre 1972 .0 F rounding ACORN 2.1 - 18.80% / raw - 49.05%

Post 1972 .0 C rounding ACORN 2.1 - 10.89% / raw - 17.99%

The first decade, 1965-1974, averaged 19.46C in ACORN 2.1 and 19.55C in raw

The final decade, 2010-2019, averaged 19.58C in ACORN 2.1 and 19.58C in raw

1987-1996 raw min averaged 19.94C and post AWS 1998-2007 averaged 19.43C

Victoria River Downs min Excel spreadsheets

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