I have often accused the local climate change denial group of shonky science in their treatment of data for their report “Are we feeling warmer yet?“ (see for example New Zealand’s denier-gate). There is the clear issue of their presenting temperature data which had not been corrected for changes in station location, etc. (And of course their unwarranted accusation that our climate scientists were guilty of fraud in using the necessary adjustments). And some of the data they used did not appear to correspond to that on the NIWA database.
Richard Treadgold (the only publicly acknowledged author of the report) consistently refused to clarify any issue I raised with him on the data. He also refused to make his data or methods available. (Although he assured me that his report was backed by his own “science team which wished to remain anonymous”). Read the emails for a summary of his attempts to avoid revealing his data and methods.
However, Treadgold seems to have inadvertently let some of his data slip by providing a link to a spreadsheet (Summary AWFWY RTreadgold.xls which is in a directory for his blog). This provides an opportunity to check in detail the level of scientific competence in this group.
Handling missing data
The spreadsheet is basically a list of temperature anomalies for the 7 stations used in the NIWA material they were critiquing. (The anomalies were presumably calculated by subtracting the average temperature for the period 1971-2000 from the actual temperate for each year. However, we don’t know that for sure unless Treadgold releases all his data and methods). Here is a screen shot for part of the spreadsheet. A notable feature is the large amount of missing data – especially in early times. Even in later years there are data gaps.
When is an average not an average?
Notice how Treadgold has calculated the average anomaly value? Simply by taking the average of the anomalies all 7 stations! Even when some data is missing. Even when he has values for only 1 station!
This completely invalidates Treadgold’s analysis.
How did NIWA handle the problem of missing values? In their original presentation of this data (the one attacked by Treadgold in his report) they did not make this mistake. Instead they used a “7-station composite” – effectively a reconstruction based on estimating missing data. In their most recent presentation (see Painted into a corner?) they removed the early data (where a lot of values are missing) because it’s reliability was questionable. They also did not have the problem of missing data in more recent times which Treadgold had.
So how might this influence the conclusions drawn by Treadgold’s report – irrespective of his big (intentional) error in refusing to adjust data for site changes?
The first graph below is the one Treadgold obtained and included in his report.
He concluded “The unadjusted trend is level—statistically insignificant at 0.06°C per century since 1850.”
But that conclusion is shonky. It includes data which are not true average anomalies.
One way of overcoming the problem is to remove the “average” anomaly for all years where there is missing data. I have done this in the figure below.
So, without the faulty data (“averages” calculated incorrectly) we get an unadjusted trend of 0.23 °C per century (0.00 – 0.56 °C per century at the 95% confidence level).
Even when Treadgold refuses to apply the necessary adjustments he can get his required conclusion only by including data which were not calculated correctly. Data he should have removed.
In his report Treadgold claimed that NZ scientists “created a warming effect where none existed.” That “the shocking truth is that the oldest readings were cranked way down and later readings artificially lifted to give a false impression of warming.” And “we have discovered that the warming in New Zealand over the past 156 years was indeed man-made, but it had nothing to do with emission of CO2 – it was created by man-made adjustments of the temperature. It’s a disgrace.”
Serious charges – but completely unwarranted. And he supported them with shonky science.
With data comes responsibility
Society has quite reasonably been demanding more openness from science – especially in important areas like climate science. Consequently much of the data scientists use has been freely available for critics to use and check. More will become available in the future.
But this example shows a problem with publicly available data. Political motivated people and organisations can make use of it to justify their own predetermined conclusions. By intentionally or unintentionally (through lack of expertise) distorting the data.
The science community has ways of eliminating, or at least reducing data distortion and subjective conclusions. This is by peer review. Not just the formal publication review but the informal checking of calculations, methods and conclusions, by colleagues.
When scientific data and conclusions are publicly discussed, in the way that NIWA’s data has been, there is surely a moral responsibility on everyo0ne involved to make their data, calculations and methods available for critique. I discussed this in my post Freedom of information an d responsibility.
The fact that Richard Treadgold has refused to do this (and only made this spreadsheet available by accident) fails that moral test.
To borrow a sentence from his infamous report – It’s a disgrace.