Drought Exceptional Circumstances

Ian Castles organized a review of the Drought Exceptional Circumstances Report by two Accredited Statisticians, who also review my first report on the skill of the climate models.

The statisticians find inadequate validation of the models of drought, as well as suboptimal regionalization in the DECR. They also find my analysis lacked force, and so I have done additional analysis in line with their suggestions.

The last few posts in the series have consisted of reviews of an unsuccessful submission to the Australian Meteorological Magazine (AMM), showing how contradictions between models and observations were suppressed from the conclusions of the DECR. These reviews cover similar ground from a different angle: the skill of the climate models in the DECR, failing to identify any real skill in the predictions of drought, and ways of showing variation between the model (increasing drought) and their real world observations (decreasing drought) at the climatic time scale.

Below are the abstracts:

Some comments on the Drought Exceptional Circumstances Report (DECR) and on Dr David Stockwell’s critique of it

K.R.W. Brewer1 and A.N. Other1
28 January, 2009

1. K.R.W. Brewer is an Accredited Statistician of the Statistical Society of Australia Inc. (SSAI) and a long term Visiting Fellow at the School of Finance and Applied Statistics within the College of Business and Economics at the Australian National University.
2. A.N. Other is a pseudonym for another Accredited Statistician of the SSAI who prefers to remain anonymous. Full responsibility for the content is taken by K.R.W. Brewer.

Abstract

The Drought Exceptional Circumstances Report (DECR) was authored by a team drawn from the CSIRO and Australia’s Bureau of Meteorology, and was publicly released in July 2008. Almost immediately it became a source of controversy. This evaluation, both of the Report itself and of the critique of it written by Dr David Stockwell, finds good mixed with less than good in both. The DECR itself is criticized for its poor delineation of Regions within Australia, for the choices made of statistics to be constructed, for the manners of their construction, and for not getting the best out of the relevant available data. Dr Stockwell is criticized for his inappropriate choices of methodology and of time periods for analysis, and also for misunderstanding some parts of what the DECR’s authors had chosen to do. Nevertheless, both the Report itself and Dr Stockwell’s critique of it are welcome stimuli to further investigate a serious issue within the climate change debate.

Validation of Climate Effect Models: Response to Brewer and Other

David R.B. Stockwell
February 4, 2009

Abstract

A review by independent Accredited Statisticians, Brewer and Other [KB09], suggested that some claims in the report “Tests of Regional Climate Model Validity in the Drought Exceptional Circumstances Report” [DS08] were premature. Additional tests suggested by KB09 support the claim made in the original report of “no credible basis for the claims of increasing frequency of Exceptional Circumstances declarations”. The contributions of KB09 and DS08 to the evaluation of skill of climate model simulations with, arguably, weakly validated idiosyncratic statistics are discussed. These include recommendations for greater rigor in evaluating the performance of climate effects simulations, such as those used in standardized forecasting practices [AG09].

One thing is clear, the climate models that all of these predictions rely on have not been validated to accepted standards. That is a major lapse on the part of the climatologists who nonetheless use the models to influence public opinion and action.

Contrast the quality and professionalism of the review by statisticians, with the error-ridden categorical reviews by climate scientists to the AMM article. The greater rigor of the statisticians is clearly evident.

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