cc: "Bamzai, Anjuli" , christopher.d.miller@noaa.gov, David Karoly , francis , Nathan Gillett , Hans.von.Storch@gkss.de, Gabi Hegerl , Jesse Kenyon , Klaus Hasselmann , Myles Allen , "Stott, Peter" , Ben Santer , Reiner Schnur , "Tett, Simon" , Karl Taylor , Tim Barnett , Tom Crowley , "Pennell, William T" , Eduardo.Zorita@gkss.de date: Fri Oct 22 14:24:33 2004 from: Phil Jones subject: RE: spring meeting to: Hans.von.Storch@gkss.de Dear Hans, I've read your email and this is a quickish reply. Apologies to all the others for filling up mail boxes with large attachments. I am still of the opinion that models should not replace reality. I may be reading too much into what you are saying, but paraphrasing/simplifying, you seem to be saying that your model and the run (ERIK) is a 'reconstruction' of the last 1000 years that can be assumed to be on a par with MBH and also with reconstructions of other groups who've put together composites based on proxy data. If I am mistaken in this sentence then forget the rest of what I say. If I'm correct in my simplifying then all you need to do to reconstruct the past is to get a good model and a reconstruction of the past history of solar forcing and explosive volcanism (and some other things like land use). I may be taking your view to its extreme. I just cannot accept that any model will ever be as good as reality. You mention ERA-40. This maybe a good reconstruction of weather over 40 years, but it is not a good reconstruction for climate purposes (see the attachment - this is an ERA-40 Report, a paper in JGR on the subject has been accepted). ERA-40 is better than NCEP is one conclusion from the work. Neither are good compared to the observations over the full 1958-2001 period. Most people who refer to Reanalyses use the word 'observations' and I always remind them they are not just simple observations. ERA-40 is clearly very good for the period from 1979, but for the 1958-78 period there are clear problems because there are not enough observations going in to correct the model bias. It is even worse, ERA-40 rejected almost all Antarctic surface data before the late 1970s because it was too far away from the first guess field. This is partly because of weights ECMWF give to different sorts of data. From the late 1970s the satellite data are much more voluminous and the model finally begins to accept the surface data. The report might be of interest to a number on this email list. I think it proves that models still have a long way to go before they can be considered as alternatives to real observed data. I'm not saying that runs like yours should not be done, just that they shouldn't be considered alternates, but be complementary and help understanding. One final thing. If boreholes are better measures of the past (which they might be), I would suggest you repeat your exercise in the Science paper with the borehole series. The locations of the holes are given on a web site in Michigan. You can spatially sample them as you've done with MBH. One thing I would like to see is whether the spatial pattern of the borehole changes (which is highly random and irregular, i.e. noisy in the boreholes) is better in your model. I'm sure it will be, but the noisy borehole data should then cast doubt on your and others beliefs that they are better representations of the past. I will be away until Nov 1. Cheers Phil At 07:09 18/10/2004, Hans.von.Storch@gkss.de wrote: Dear Phil, I want to respond to this: " There is no way I can accept Hans that your reconstruction (because it uses no proxy data) can be a reasonable reconstruction. The only reconstructions we should be considering of the past are those based on proxy data. Your paper is what you said a methodological critique - not a replacement/alternative. Models should never replace reality. Models can help our understanding, telling us how to use our data better." First, I regret if again my English language skills failed. Second I want to respond that your assertion about the utility of models is too limited. 1) Let's use the lingua franca of these days. Mathematics. Let's consider the function f, which maps a full "true" NH mean temp, given by noisy, spatially spotty and not always homogeneous data, with the help of the MBH math, onto a "MBH" best guess. f: T -> M. Let's call the hockeystick M*. Question is, how big is the set f-1(M*)? (f-1 the inverse of f). We claim that our model-based ERIK curve E is in f-1(M*). That what I meant with "reasonable". Likely not a good choice of words. In any case, as you rightly say: it's a matter of "can" not of "is". Our curve E "could" be close to the true curve, because f(E) = M*. (of course only a qualitative argument, to avoid my English language insufficiencies.) But the set f-1(M*) likely contains more elements than E, that is: more NH distributed states are "reasonable" reconstructions. I suggest, that M* is NOT in f-1(M*), that it is not f(M*)=M*. If true, MBH can not deliver the true curve T, since this needs f(T)=M*. (= meant as "approximately equal".) But we have not yet demonstrated that. 2) The statement that "The only reconstructions we should be considering of the past are those based on proxy data" is a normative statement and not based on science. Would you say that ERA is not a good reconstruction of the past 40 years' weather, even though it is based on a mixture of direct INSTRUMENTAL evidence and of model dynamics? Would you say that the concept of state space formulations is not meaningful for the analysis of real word developments? (In parenthesis - do you claim that tree ring data provide data about the physical climate state, or would you accept that physical knowledge claims coming out of an analysis of tree rings is a mixture of empirical ecological evidence (tree ring characteristics) plus an empirical model based on somewhat limited knowledge? Tree ring data do not provide data about temp etc; they give estimates based on certain assumptions, or, if you like: models. I learned that from you, on Elba, during our summer school.) Our paper is indeed just a methodical critique, and if we believe the quotes ascribed to Mike Mann in some media, then the problem of the MBH method in specifying low frequency variability was long known. Question is how the curve with such significant, allegedly known deficits could get such a celebrity status? The conclusion of our paper is that ALL regression-based methods have this problem as long as the correlation are not high for the low-frequencies. Borehole curves, which are based on the inversion of a physical model may fare better; methods based on inflation have other methodical problems. Fur the time being, we can not expect to get significantly better (in the sense of getting more robust scalable information about low-frequencies) information from proxy data; also better statistical models can also not be constructed, as long as we do not know how to filter out the non-climatic effects in proxy data. We need a new approach, and the only one I see is the state-space formalism - i.e., complex models to describe the dynamics, and adequate dynamical models describing consistently the generation of proxy data and the evolution of climate. Models can more than "help our understanding, telling us how to use our data better." What we need to do in future is to discuss more openly, and to be less aggressive against people proposing different approaches. We have to think about how to combine the empirical evidence with theoretical knowledge. And we should stop factoring into our discussion the concern that skeptics will misuse what we do and say. That is - normative statement! - bad science. All the best Hans Hans von Storch Institute for Coastal Research, GKSS Research Center Max-Planck-Strasse 1, 21502 GEESTHACHT, Germany ph: +49 4152 87 16830, fx: +49 4152 87 2832 mobile: + 49 171 212 2046 [1]http://w3g.gkss.de/staff/storch; storch@gkss.de Prof. Phil Jones Climatic Research Unit Telephone +44 (0) 1603 592090 School of Environmental Sciences Fax +44 (0) 1603 507784 University of East Anglia Norwich Email p.jones@uea.ac.uk NR4 7TJ UK ----------------------------------------------------------------------------