By Bob Irvine -Re-Blogged From WUWT
Darwin Australia is one of only two temperature stations in an entire NASA grid and, therefore, has a disproportionate influence on the NASA-GISS global temperature reconstruction. The other station used by NASA in this grid is Gove (Stn. # 014508). Gove only goes back to 1985 which leaves Darwin as the only station in this grid that dates back to the early part of the 20th century.
Jennifer Marohasy has been an absolute warrior in pursuit of the Australian Bureau of Meteorology (BOM). She has doggedly confronted their bureaucratic maze and called out their consistent and brazen manipulation of Australian temperature data. Her blog post on the recent changes to historical Darwin temperatures is copied below.
I have used a couple of her plots and added a few of my own in this post.
Apart from the obvious mismatch with the early Post Office data, the period from about 1940 to the late 1070’s has also been lowered by about half a degree.
The difference between the raw Darwin temperatures and the official BOM temperature in Fig. 1 is quite stark and clearly needs to be looked at.
There are only three series that extend from 1910 to the present that are anywhere near Darwin.
They are Richmond which is about 1800km away. Marble Bar about 1800 km away and Alice Springs about 1400 km away. Minimally homogenized Darwin raw temperatures, that allow for the station move, have been overlaid on the raw Richmond series and this is followed by the other two series below.
Presumably these three series were used to homogenize Acorn-Sat version 2 (Darwin) to now show nearly 2.0C warming from 1910 to the present. They are the nearest series to Darwin that cover this period. It is simply inconceivable that Marble Bar and Richmond temperatures could have fallen slightly over this period while Darwin temperatures rose by an astounding 2.0C as BOM are now saying. This is especially true when we consider that Darwin raw temperatures also show a small decline in temperature over 100 years or more.
There are 62 Australian locations that have raw temperature data going back to or close to 1910. The station data can be found at; http://www.bom.gov.au/climate/data/
Most of these locations have continuous station numbers and should, therefore, be a valid record for the period and place specified. To quote the BOM;
“The Bureau of Meteorology station number uniquely specifies a station and is not intended to change over time, although on very rare occasions a station number may change or be deleted from the record (usually to correct an error). Generally, a new station number is established if an existing station changes in a way that would affect the climate data record for that site (measured in terms of air temperature and precipitation). Significant station moves are an example of this.”
1. Out of these 62 locations there are 25 locations that strictly cover the period 1910 to 2010.
a. Their station #s are; 015540/015590, 38003 R, 9510 R, 031010/031011, 9518 R, 90015 R, 048030/048027, 9534 R, 55023 R, 94029, 012039/012038, 10579 R, 10073, 86071, 076077/076031, 9581, 10111 R, 28004, 30045 R, 26026 R, 66062, 33047 R.
Their average Max. trend is 0.07C/Decade. Their average Min. trend is 0.09/Decade. Total average trend 0.08C/Decade.
2. A subgroup of these 25 stations are 11 rural stations. They are marked “R” above.
Their average Max. trend is 0.04C/Decade. Their average Min. trend is 0.09C/Decade. Total average trend 0.065/Decade.
In 2012 the BOM homogenised this data and added approximately 50 shorter more recent homogenised series to these to come up with an increase in the mean temperature for Australia since 1910 of 0.95°C or 0.095°C/Decade. This was calculated as the mean of the increase in maximum temperature of 0.8°C and the increase of 1.1°C in the minimum temperature. This homogenised data set is known as Acorn-Sat 1.
It can be seen that the BOM homogenisation process and the addition of the extra series has increased this raw trend.
When data that strictly covers 1910 to 2010 is used then this increase is from 0.8 to 0.95.
When rural data that does not include a UHI affect is used then this increase is from 0.65 to 0.95.
These figures from the raw data are very close to the global averages.
In January 2019 the BOM increased their increase from 1910 to 2018 for Australia from 0.95 to 1.23C. This is nearly double the rural raw data figure to 2010 above. This is an outlier when compared to global trends and is known as Acorn-Sat 2.
In June 2015 the Acorn-Sat Report of the Technical Advisory Forum explained these changes as follows;
The effect of homogenisation
The chart below (Fig 4.1) shows the difference in mean temperature anomalies between the homogenised ACORN-SAT and unadjusted AWAP datasets for Australia. Since 1960, there is a noticeable convergence between the raw and adjusted datasets, which most likely reflects the relative increase in the observing station network density over time.
The Forum considers that its own recommendations will deliver improvements to the management and communication of the ACORN-SAT dataset. There is a clear trend increase in both the raw and homogenised temperature data, and the temperature patterns exhibited in a variety of other datasets have a similar character. It is not currently possible to determine whether these improvements will be reflected in an increased or decreased warming trend that has been broadly observed across a range of different datasets.
Fig 4.1: Scatter plot of the difference between ACORN-SAT and AWAP mean temperature anomalies
Australian Climate Observations Network (Acorn-Sat)
Report of the Technical Advisory Forum. June 2015
It is clear from their Fig, 4.1 that they have artificially cooled temperatures significantly before 1960. This report was done in 2015 and comments on Acorn-Sat version 1 from 2012. Acorn-Sat 2 has doubled this artificial cooling of historical temperatures.
The “Forum” commentary does not attempt to discuss this artificial historical cooling and focuses entirely on the post 1960 period that matches reasonably well. This appears to be a little disingenuous. It is also clear that the measured temperature since 1980 has been artificially warmed slightly. The overall affect of these adjustments is exaggerated 20th century warming that suspiciously gives support to the global warming meme.
Fig. 4, Climategate email di2.nu/foia/1254108338.txt