Northern Territory has the lowest population and lowest population density of any state in Australia. It also has the lowest number of long and medium weather stations (other than ACT). In total only 20 temperature records contain more than 480 months of data, and only three of these have more than 1200 months of data.
Fig. 23.1: The locations of long stations (large squares) and medium
stations (small diamonds) in Northern Territory. Those stations with a high warming trend
since 1851 are marked in red.
The three long records are for Alice Springs Airport, Tennant Creek Post Office and Darwin Post Office. Of these, Alice Springs is the longest, while only Tennant Creek displays a strong warming trend (0.86 °C per century according to Berkeley Earth). The trend for Alice Springs is a modest 0.23°C per century, while for Darwin it is negative (-0.55°C per century).
Despite being low in number, the stations in Northern Territory are fairly evenly distributed (see Fig. 23.1 above). This means that when the average of all the Berkeley Earth adjusted anomalies are calculated for each month, the resulting overall trend that is produced using my simple averaging process for that data (and plotted in Fig. 23.2) is very similar to that claimed by Berkeley Earth using their weighted averaging process (see Fig. 23.3).
ii) The Berkeley Earth (BE) mean temperature trend
Fig. 23.2: Temperature trend for all long and medium stations in Northern Territory
since 1879 derived using the Berkeley Earth adjusted data. The best fit
linear trend line (in red) is for the period 1921-2003 and has a
gradient of +1.17 ± 0.06 °C/century.
The Berkeley Earth trends in Fig. 23.3 below clearly exhibit a slight cooling from 1880 up to 1920, followed by a much stronger warming. This is replicated in my reconstruction of those trends based on a simple average of the Berkeley Earth adjusted anomalies, as shown in Fig. 23.2 above.
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 correspond to similar features at almost identical times in the official Berkeley Earth trend shown below in Fig. 23.3 and published online here. This implies that only a simple average of the data from Northern Territory 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.
This also suggests that the trend of the warming period in Fig. 23.2 above, which is approximately 1.17 ± 0.06 °C per century and denoted by the red line, will also correspond to the warming trend post-1920 in Fig. 23.3 below. This warming trend equates to a total warming since 1920 of about 0.97 °C.
Fig. 23.3: Temperature trend for Northern Territory since 1840 according to Berkeley Earth.
There is, though, one slight problem with the above analysis: it doesn't correspond to reality. By reality I mean what the actual, original, raw data would indicate. For if we repeat the above analytical procedure, but use the original raw data instead of the Berkeley Earth adjusted data, then the picture is entirely different.
iii) Temperature trend based on long and medium station records
To do this we first must calculate the anomaly for each month of each temperature record using the monthly mean from 1961-1990 using only the data from that record. These 12 monthly mean values are what I term the monthly reference temperatures (MRTs) and the procedure used to determine them I described earlier in Post 5. This process does not use the homogenization that appears to occur in the Berkeley Earth process. In a future post I will show evidence of this automated homogenization, specifically in relation to some data I found from Zimbabwe that has been incorrectly attributed, and which thereby highlights the rationale at the heart of the Berkeley Earth process.
Next, the anomalies for each month are calculated by subtracting the MRTs from the raw data. Then the monthly anomalies from different records averaged. The result is shown in Fig. 23.4 below.
Fig. 23.4: Temperature trend for long and medium stations in Northern Territory
since 1879. The best fit linear trend line (in red) is for the period 1882-2007 and has a gradient of -0.13 ± 0.07 °C/century.
The data in Fig. 23.4 is pretty unambiguous. It shows that there has been no warming of the climate in Northern Territory over the last 140 years. In fact the mean temperature has declined by about 0.2 °C over that time. The principal reason for the discrepancy between this data and the Berkeley Earth adjusted data is down to the adjustments made by Berkeley Earth. These are due to our old friends homogenization and breakpoints (see Fig. 23.5 below).
iv) Breakpoints and other adjustments
Fig. 23.5: 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 1881-2010 (red line).
The gradient of the best fit line is +0.62 ± 0.03 °C per century. The
yellow curve represents the contribution made to the difference data by breakpoint adjustments.
The data in Fig. 23.5 highlights the impact of both homogenization and breakpoint adjustments. The data in Fig. 23.5 is derived by subtracting the mean temperature anomaly shown in Fig. 23.4 from the Berkeley Earth adjusted anomaly. The difference is the total adjustment made by Berkeley Earth to the data for each month.
It can be seen that in combination these adjustments could potentially add 0.62 °C per century to the overall temperature trend. Between 1881 and 2010 this amounts to a temperature rise of more than 0.8 °C. In other words, almost all the temperature rise reported by Berkeley Earth for Northern Territory data in Fig. 23.3 can be attributed (depending on your point of view on how the data should be analysed) to inputs made by Berkeley Earth through their adjustment processes.
If this all sounds a bit noncommittal and ambiguous on my part, it is because it highlights what is in my view the central crux of the whole global warming debate. This is that the data is not complete, definitive and unambiguous, and therefore that all forms of analysis of that data are subjective, even the ones I have outlined in this blog. That is why all possible interpretations and explanations for climate change phenomena need to be considered, not just the prevailing orthodoxy. The issue, therefore, is not that Berkeley Earth and other climate scientists are definitely wrong, but that they might be.
v) Conclusions
1) According to the raw data, there has been no warming of the climate in Northern Territory since 1880.
2) The mean temperature in Northern Territory has declined by about 0.18 °C since 1880.
3) Adjustment processes used by climate scientists to process and average the temperature data could be responsible for virtually all of the temperature rise they claim has occurred in Northern Territory since 1900.
No comments:
Post a Comment