cc: Jerry Meehl , Caspar Ammann date: Fri, 16 May 2003 14:18:36 -0600 from: Tom Wigley subject: Soon et al. paper to: "Michael E. Mann" , Phil Jones , Keith Briffa Dear folks, I have just read the Soon et al. paper in E&E. Here are some comments, and a request. Mike said in an email that he thought the paper contained possibly 'legally actionable' ad hominem attacks on him and others. I do not agree that there are ad hominem attacks. There are numerous criticisms, usually justified (although not all the justifications are valid). I did not notice any intemperate language. While many of the criticisms are invalid, and some are irrelevant, there are a number that seem to me to be quite valid. Probably, most of these can be rebutted, and perhaps some of these are already covered in the literature. In my view, however, there a small number of points that are valid criticisms. [Off the record, the most telling criticisms apply to Tom Crowley's work -- which I do not hold in very high regard.] The real issue that the press (to a limited extent) and the politicians (to a greater extent) have taken up is the conclusions of the paper's original research. First, Soon et al. come down clearly in favor of the existence of a MWE and a LIA. I think many of us would agree that there was a global-scale cool period that can be identified with a LIA. The MWE is more equivocal. There are real problems in identifying both of these 'events' with certainty due to (1) data coverage, (2) uncertainty in transfer functions, and (3) the noise of internally generated variability on the century time scale. [My paper on the latter point is continually ignored by the paleo community, but it is still valid.] So, we would probably say: there was a LIA; but the case for *or against* a MWE is not proven. There is no strong diagreement with Soon et al. here. The main disagreements are with the methods used by Soon et al. to draw their LIA/MWE conclusion, and their conclusion re the anomalousness/uniqueness of the 20th century (a conclusion that is based on the same methods). So what is their method? I need to read the paper again carefully to check on this, but it seems that they say the MWE [LIA] was warm [cold] if at a particular site there is a 50+ year period that was warm, wet, dry [cold, dry, wet] somewhere in the interval 800-1300 [1300-1900], where warm/cold, wet, dry are defined relative to the 20th century. The problems with this are ..... (1) Natural internally generated variability alone virtually guarantees that these criteria will be met at every site. (2) As Nev Nicholls pointed out, almost any period would be identified as a MWE or LIA by these criteria -- and, as a corollary, their MWE period could equally well have been identified as a LIA (or vice versa) (3) If the identified warm blips in their MWE were are different times for different locations (as they are) then there would be no global-mean signal. (4) The reason for including precip 'data' at all (let alone both wet and dry periods in both the MWE and LIA) is never stated -- and cannot be justified. [I suspect that if they found a wet period in the MWE, for example, they would search for a dry period in the LIA -- allowing both in both the MWE and LIA seems too stupid to be true.] (5) For the uniqueness of the 20th century, item (1) also applies. So, their methods are silly. They seem also to have ignored the fact that what we are searching is a signal in global-mean temperature. The issue now is what to do about this. I do not think it is enough to bury criticisms of this work in other papers. The people who have noticed the Soon et al paper, or have had it pointed out to them, will never see or become aware of such rebuttals/responses. Furthermore, I do not think that a direct response will give the work credibility. It is already 'credible' since it is in the peer reviewed literature (and E&E, by the way, is peer reviewed). A response that says this paper is a load of crap for the following reasons is *not* going to give the original work credibility -- just the opposite. How then does one comprehensively and concisely demolish this work? There are two issues here. The first is the point by point response to their criticisms of the literature. To do this would be tedious, but straightforward. There will be at least some residual criticisms that must be accepted as valid, and this must be admitted. Cross-referencing to other review papers would be legitimate here. The second is to demolish the method. I have done this qualitatively (following Nev mainly) above, but this is not enough. What is needed is a counter example that uses the method of reductio ad absurdem. This would be clear and would be appropriate since it avoids us having to point out in words that their methods are absurd. I have some ideas how to do this, but I will let you think about it more before going further. You will see from this email that I am urging you to produce a response. I am happy to join you in this, and perhaps a few others could add their weight too. I am copying this to Jerry since he has to give some congressional testimony next week and questions about the Soon et al work are definitely going to be raised. I am also copying this to Caspar, since the last millenium runs that he is doing with paleo-CSM are relevant. Best wishes, Tom.