Demetris Koutsoyannis was at two sessions of the 11th Meeting on Statistical Climatology in Edinburgh last week. The purpose of the meetings is:
The aim of IMSC is to promote good statistical practice in the atmospheric and climate sciences and to maintain and enhance the lines of communication between the atmospheric and statistical science communities.
Geoffrey Boulton’s associate, Gabrielle Hegerl, was an organizer. One of the important sessions was entitled “Reconstructing and understanding climate change over the Holocene”.
Demetris’ presentation is online here, poster here. I urge readers to look closely at his interesting example showing how very high autocorrelation can arise from a compound stochastic process consisting of:
(1) random changes of level persisting for exponentially distributed lengths;
(2) white noise.
It’s a different sort of stochastic process than the all-too-artificial ARMA processes that dominate present-day analyses and well worth paying attention to.
Demetris wrote me to say that he attended on Tuesday and Wednesday, including the session “Reconstructing and understanding climate over the Holocene” (see p. 18 in the “final program and logistics“, commending the first presentation by Heinz Wanner (Holocene climate change – facts and mysteries).
He said that Mann’s talk included an interesting cartoon with an ensemble of hockey sticks, one of which is being broken by an angry guy.
He reported that Climategate came up in a talk by Reinhard Böhm, who, according to Demetris, “promoted a thesis that it is dangerous to put raw data open on the internet because some they would misuse them.” Demetris said that, in his own talk the next day, he tried to respond to this (and “to comment on Mann’s cartoon with the ensemble of hockey sticks–but Mann wasn’t there”).
Demetris sends the following extended commentary on his exchange with Böhm.
One of the interesting talks I attended in the 11th International Meeting on Statistical Climatology (http://cccma.seos.uvic.ca/imsc/11imsc.shtml, University of Edinburgh, Scotland, 12-16 July 2010) was that by Reinhard Böhm. He is the author or a recent (2008) book in German, “Heiße Luft – Reizwort Klimawandel: Fakten – Ängste – Geschäfte” (Hot air: the climate change controversy – facts – fears – funding). His talk was given in the session “Climate Data Homogenization and Climate trend/Variability Assessment” and was entitled “Bridging the gap from indirect to direct climate data – experience with homogenizing long climate time series in the early instrumental period”. The long abstract can be seen in p. 90 of the book of abstracts, accessible from http://cccma.seos.uvic.ca/imsc/11imsc/final_program_abstracts.pdf. In his talk he referred to Climategate and discussed the question whether original climatic data should be available to the public or not. His main point was that the original data are contaminated with biases and inhomogeneities and thus need homogenization. Therefore, only processed data are useful and should be available to the public.
I disagree with this thesis and I addressed three questions to him in the end of his talk:
1. If I homogenize a data set of an area, do you think that there might be a possibility that I introduce more biases that originally contained?
2. If you studied the climate of that area would you rely solely on my processed data or would you retrieve also the original data?
3. Do you think that the original data should be available to the interested scientists or not?
In my question 1 he replied “yes”, which I appreciate, given that I believe that standard procedures for consistency checking and homogenization are strongly affected by inappropriate statistical assumptions (e.g. iid variables with exponential distribution tails), which are invalidated in the real word. In question 2 he replied that if I give explanation of the procedures I followed he would rely on my processed data. About question 3 he said (if understood well) that its reply would need a long time, but in brief the raw data should not be available on the internet because some could misuse them, e.g. choosing only a few stations that demonstrate a specific behaviour that they want to advocate.
I was not happy about the last answer and, next day, I found the opportunity to reply indirectly, using the first slide of my own talk (http://www.itia.ntua.gr/en/docinfo/991/), which contains the title and the web link to my presentation. I said that the online availability is not just for this presentation. Rather, in my group we believe in transparency and have agreed that everything we produce, papers, reports, data, etc., should be openly available on the internet. And I continued “Please feel free to misuse them but, also, please be advised that transparency is the most powerful weapon against misuse”.