i) Weather station quality and distribution
Queensland is the second largest state by area in Australia, but only the third largest by population. Given that the provision of weather station records around the world appears to broadly correlate with a combination of population and GDP, one would therefore expect Queensland to have more temperature records than smaller states such as Tasmania, South Australia and Northern Territory, but less than states with larger populations such as Victoria and New South Wales (NSW). This is broadly the case, although not in the case of Victoria.
Queensland has 112 stations with over 480 months of data (medium stations), of which 28 are long stations with more than 1200 months of data. This is not as extensive as NSW but more than Victoria. However, while Victoria has fewer stations in total, those long stations that it does have tend to have longer records. The major deficiency of the Queensland temperature records is that none pre-date 1887.
Fig. 24.1: The locations of long stations (large squares) and medium
stations (small diamonds) in Queensland. Those stations with a high warming trend
since 1887 are marked in red.
If we look at the distribution of weather stations in Queensland (see Fig. 24.1 above) we see that it is fairly even. There is a higher concentration around Brisbane and the Coral Sea coast compared to inland, but the coverage is generally fairly good, if a little sparse around the border with South Australia.
ii) The Berkeley Earth (BE) mean temperature trend
As the stations in Queensland are fairly evenly distributed (see Fig. 24.1 above), it means weighting coefficients based on the local station density are not necessary when combing stations into a regional average. This can be seen when averaging all the Berkeley Earth adjusted anomalies for each month. The resulting overall trend that is produced using a simple averaging process for that data (and plotted in Fig. 24.2) is very similar to that claimed by Berkeley Earth using their weighted averaging process (see Fig. 24.3).
Fig. 24.2: Temperature trend for all long and medium stations in Queensland
since 1887 derived using the Berkeley Earth adjusted data. The best fit
linear trend line (in red) is for the period 1951-2003 and has a
gradient of +1.74 ± 0.14 °C per century.
The Berkeley Earth trend in Fig. 24.2 above is my reconstruction of the Berkeley Earth adjusted trend. It was derived simply by averaging the adjusted anomalies for all long and medium stations. These adjusted anomalies were found in the data files for each station on the Berkeley Earth site. An example for Brisbane Regional Office Roof (Berkeley Earth ID: 152224) is found here. The adjusted anomaly data is in the 8th column. The raw temperature data is in the 3rd column.
The temperature trend in Fig. 24.2 clearly exhibits a period of stability from 1880 up to 1950, followed by a much stronger warming phase. This is replicated in the official Berkeley Earth version shown in Fig. 24.3 below, the original online version of which can be found here.
It is apparent that most of the prominent features (i.e. major peaks and troughs) displayed by both the 12-month moving average and the 10-year moving average for my reconstruction from the Berkeley Earth adjusted anomalies (shown in Fig. 24.2 above) correspond to similar features at almost identical times in the official Berkeley Earth trend shown below in Fig. 24.3. This implies that only a simple average of the data from Queensland is necessary in order to determine the overall trend for the region, and no station weighting (either based on their area of coverage or statistical significance) is needed.
Fig. 24.3: Temperature trend for Queensland since 1840 according to Berkeley Earth.
The degree of agreement between the data in Fig. 24.2 and Fig. 24.3 also suggests that the trend of the warming period in Fig. 24.2 above, which is approximately 1.74 ± 0.14 °C per century and denoted by the red line, will also correspond to the warming trend post-1920 in Fig. 24.3. This warming trend equates to a total warming since 1951 of about 1.0 °C. If we look at the raw temperature data though (rather than the Berkeley Earth adjusted data), we get a slightly different picture.
iii) Temperature trend based on long and medium station records
In this section I have applied the same simple averaging process to the raw temperature anomalies as was deployed in the last section for the Berkeley Earth adjusted anomalies. The raw anomalies for each dataset were derived by subtracting the monthly reference temperature (MRT) for that dataset from each monthly reading in that dataset. The 12 different MRTs were derived by averaging the temperature for each month in the dataset over the period 1961-1990. Then the mean anomaly for each month was determined by averaging all the values for that month from the different station datasets. The result is the regional monthly average shown in Fig. 24.4 below.
Fig. 24.4: Temperature trend for long and medium stations in Queensland
since 1887. The best fit linear trend line (in red) is for the period 1901-2004 and has a gradient of 0.74 ± 0.08 °C per century.
The temperature trend in Fig. 24.4 is clearly positive over the entire time-frame, although the upward trend is more pronounced after 1950. This is different from the trend for all the other states in Australia, most of which exhibited a clear downward temperature trend before 1940. This difference may be due to the lack of data in Queensland before 1890, or it may be the result of regional variation. It should also be noted though that the trend for Queensland in Fig. 24.4 is very similar to that found for South Australia from 1900 onwards (see Fig. 21.5 here). Overall, the trend in Fig. 24.4 amounts to a total temperature rise since 1890 of 0.89 °C. This is slightly less than that seen for the Berkeley Earth adjusted data in Fig. 24.2.
iv) Breakpoints and other adjustments
Subtracting the mean temperature anomaly shown in Fig. 24.4 from the Berkeley Earth version derived using adjusted anomalies yields the data in Fig. 24.5 below.
Fig. 24.5: The difference between the raw anomaly data in Fig. 23.4 and Berkeley Earth adjusted anomaly data,
together with a linear best fit for the period 1901-2010 (red line).
The gradient of the best fit line is +0.02 ± 0.04 °C per century. The
yellow curve represents the contribution made to the difference data by breakpoint adjustments.
The data in Fig. 24.5 appears to indicate that the Berkeley Earth adjustments are more or less neutral. This is not true, for while the overall contribution to the trend curve is minimal, there are within this two separate contributions which are not.
The first is for the period 1887-1950. Here the adjustments raise the temperatures before 1990, thereby flattening the curve. Then after 1951 the contribution is to increase the slope. The slope of the adjustments after 1951 is +0.15 ± 0.09 °C per century, while before 1951 it is -0.42 ± 0.09 °C.
Fig. 24.6: The contribution of Berkeley Earth adjustments to the anomaly data after smoothing with a 12-month moving average. The linear best fit to the data is for the period 1901-2010 (red line) and the gradient is +0.02 ± 0.04 °C per century. The orange curve represents the contribution made to the adjustment curve by breakpoint adjustments only.
The significant feature of the total adjustment data in Fig. 24.5 (the blue curve with black markers) is the amount of noise it contains, amounting to fluctuations of up to ±0.5 °C. Remarkably, a 12-month moving average completely removes this noise. This implies that the fluctuations are not random, but are periodic, with a period of 12 months. The obvious source of these fluctuations is the difference in the MRT between the values I have derived in my calculation of the temperature anomaly, and the homogenized values used by Berkeley Earth that also rely on data from neighbouring station records.
v) Conclusions
1) Queensland is the only state in Australia that exhibits a significant warming trend.
2) It is also the only state with no evidence of warming before 1890. That is because it is the only state with no significant data before 1890 (other than ACT).
3) The total temperature rise since 1890 is less than 0.9 °C.
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