Last night George Christensen MP gave a speech accusing the Bureau of Meteorology of “fudging figures”. He waved a 28 page of adjustments around, and called for a review. These adjustments can be found here. While I dont agree that adjusting to account for station moves can necessarily be regarded as fudging figures, I am finding issues with the ACORN-SAT data set.
The problem is that most of the adjustments are not supported by known station moves, and many may be wrong or exaggerated. It also means that if the adjustment decreases temperatures in the past, claims of current record temperatures become tenuous. A maximum daily temperature of 50C written in 1890 in black and white is higher than a temperature of 48C in 2014, regardless of any post-hoc statistical manipulation.
But I do take issue with a set of summaries being released as blatant “cherry-picking”.
Scroll down to the bottom of the BoM adjustment page. Listed are station summaries justifying the adjustments to Amberley, Deniliquin, Mackay, Orbost, Rutherglen and Thargomindah. The overlaps with the ones I have evaluated are Deniliquin, Rutherglen and Amberley (see previous posts). While the BoM finds the adjustments to these stations justified, my quality control check finds problems with the minimum temperature at Deniliquin and Rutherglen. I think the Amberly raw data may have needed adjusting.
WRT Rutherglen, BoM defends the adjustments with Chart 3 (my emphasis):
Chart 3 shows a comparison of the raw minimum temperatures at Rutherglen with the adjusted data from three other ACORN-SAT stations in the region. While the situation is complicated by the large amount of missing data at Rutherglen in the 1960s, it is clear that, relative to the other sites, Rutherglen’s raw minimum temperatures are very much cooler after 1974, whereas they were only slightly cooler before the 1960s.
WRT Deniliquin, BoM defends the adjustments on Chart 3 (my emphasis):
Chart 3 shows a comparison of minimum temperatures at Kerang (95 km west of Deniliquin) and Deniliquin in the years around 1971. Deniliquin is consistently warmer than Kerang prior to 1971, with similar or cooler temperatures after 1971. This, combined with similar results when Deniliquin’s data are compared with other sites in the region, provides a very clear demonstration of the need to adjust the temperature data.
My analysis is superior to flawed the BoMs analysis in 3 important ways:
1. I compare the trend in Rutherglen and Deniliquin with 23 and 27 stations respectively, not 3 and 1 neighbouring stations respectively (aka cherry-picking).
2. I also use a rigorous statistical panel test to show that the trend of the Rutherglen minimum exceeds the neighbouring group by O.1C per decade, which is outside the 95% confidence interval for Australian stations trends — not a visual assessment of a chart (aka eyeballing).
3. I use the trends of daily data and not annual aggregates, which are very sensitive to missing data.