Just as a quick look at the data provided from CSIRO for the Drought Exceptional Circumstances Report, I made density plots (frequency histograms) for the rainfall data over two periods, 1900-2010 and 2010-2040 for the South-west of Western Australia, the area with the highest drought predictions. The plot below is the result, with the past in blue and the future in red. You can see the extremely skewed distribution of the data, with a large number of zeros (no drought areas). The future data (red) has a bump at the right hand end of the plot indicating a higher frequency of 100% drought declared areas than the past data.
This started out as a request to CSIRO for data used in coming to conclusions in the Drought Exceptional Circumstances Report, which spawned a series of posts and some furore when the data were not forthcoming immediately. Kevin Hennessy of CSIRO informs me that the data are now available on the BoM website. Credit is due to Kevin for making this happen, as he had to get the permission of all parties to the report, the Dept of Agriculture, Fisheries and Forestry, Bureau of Meteorology and the CSIRO, before the data could be released. I will post the results when I have them. In the meantime, I was reflecting on reasons why people should share data:
David Evans , aka ‘rocket scientist‘, shared his progression from a believer in anthropogenic global warming (AGW) to skeptic in response to new evidence (longer article here). Bayesian updating is a way of modeling rational changes of mind. I want see if DE is a rational, thinking person. Dr. Jim Peacock, Chief Scientist of Australia, immediate past President of the Australian Academy of Science and a Fellow of the Royal Society of London thinks not. Using the evidence presented in his article, and a very simple Bayesian updating system, we can model the changing probabilities of AGW in DE’s mind. Bayesian updating can get very complicated, but I am going to show a very simple way of simulating it.
A superb opinion piece published recently in The Australian graphs one scientists conversion from AGW believer to skeptic after failing to find evidence. David Evans is the self-confessed rocket scientist who wrote the custom carbon accounting model (FullCAM) that measures Australia’s carbon credit in the land use change and forestry sector. In disagreeing with mainstream science as represented by the IPCC he is among those that Professor Garnaut indecorously refers to as ‘dissenters’ here or even ‘deniers’ here.
Attempts to get some summary data from the Drought Exceptional Circumstances report out of Australia’s scientific organization CSIRO, in order to check the statistical significance of the results, have been described as a saga. The way this has been picked up on various blogs and comments shows the depth of concern people have about data access for checking scientific work. Read the rest of this entry…
The Intellectual Property card was played today so I cannot verify the statistical significance (or otherwise) of the Drought Exceptional Circumstances Report. But I found out enough about the statistical tests (performed after publication of the report due to my promptings) to determine that autocorrelation in the temperature series was probably not taken into account. Read the rest of this entry…
Today I received a reply from CSIRO regarding the Drought Exceptional Circumstances Report. I was very pleased that Mr Hennessy expresses an interest in providing the data needed to check the results, and will refrain from further comment until I get the data and analyze it. Read the rest of this entry…
It was described by the ABC and Agriculture Minister Tony Burke as like “a disaster novel”, but a simple test shows the drought predictions are not statistically significant, apart for the SW of Western Australia. The conclusions should read: Read the rest of this entry…
The Drought Exceptional Circumstances report has been released (and reviewed here). The ABC described it thusly: “A new report is predicting a dramatic loss of soil moisture,
increased evaporation and reduced ground water levels across much of
Australia’s farming regions, as temperatures begin to rise
exponentially.” The Bureau of Meteorology and CSIRO report was described by Agriculture Minister Tony Burke as like “a disaster novel”. This just days after the far-reaching policy on an emissions trading scheme, the Garnaut Report. Read the rest of this entry…
The Draft Garnaut Report is to be commended for commissioning a study Global temperature trends – Breusch and Vahid (BV) by two prominent Australian National University (ANU) econometricians to examine global temperature series. The approach they take to modeling temperature has a long history. See for example at RealClimate, Rybski, and Koutsoyiannis. Their findings that the significance barely reaches the 95% level with these kinds of models is not inconsistent with any of them. Even if there are no new insights, independent statistical studies by experts outside the field help to build trust and confidence in a controversial issue.
However, the results of the study are no reason for ‘high fives’ among proponents of man-made global warming. Despite concluding that “the temperatures recorded in most of the last decade lie above the confidence level produced by any model that does not allow for a warming trend”, the study also reveals just how close the case for anthropogenic global warming is to a spurious regression on a random walk.
Below are some of the issues that have been raised about the paper on the various climate blogs.
The Garnaut report on regulating carbon emission is due to be made public today. According to The Australian, Professor Garnaut’s 600-page report will provide detailed analysis of how climate change will affect the Australian economy and what should be done to combat the issue. The article mentions emissions trading scheme, black-outs, bankruptcies and spiralling power bills.
Along with 4000 others, I made a submission on the Interim Report, argued the case for more involvement of statisticians, and supported with a summary of the sensitivity testing and conversations with Rahmstorf on this blog. The one page article published in Science, claimed to show that the climate was responding at a faster rate than the climate models predict. Ironically, the publication marked the start of over 12 months decline in global temperatures dubbed ‘Rahmstorf’s drop‘. I think it is supposed to be getting warmer, not colder.
