cc: m.hulme@uea.ac.uk date: Fri, 01 Oct 1999 10:18:41 +0100 from: Phil Jones subject: Paper 980G by Luterbacher et al to: b.d.mcgregor@bham.ac.uk Dear Glenn, I've tried to ring you to talk about this paper that IJC has rejected on 21/9/99. My interest is that I'm one of the et al's. I've talked to Mike here about it and he suggested I contacted you about the decision. Your decision has been made on the basis of one reviewer only. I know from Jurg Luterbacher that you've had difficulty getting a second reviewer to respond. We (me, Mike and the Swiss) think we have a real grievance and are questioning the decision. Fortunately Mike didn't attend the last IJC meeting otherwise I might have been able to find out who this well respected referee is. I know I shouldn't have asked Mike but I was so annoyed with the two main comments that I asked him ! His two points are basically wrong ! 1) 'Patterns during the 20th century are applicable to earlier epochs'. This assumption applies to all paleo reconstruction papers ever written. OK, it is an assumption called the 'Principal of Uniformitarianism' and we could have stated it clearer, but it is one that has been made by countless thousands before us. If it is not valid we might as well give up. The method used in the paper is not the same as infilling SST fields to get complete fields, a technique that I would question ( this technique is usually used to get complete fields to drive GCMs). Our paper uses real data for the past and attempts through a calibration/verification exercise to derive circulation patterns for earlier periods. The only real requirement for the technique to work properly is that all the long time series used in the reconstructions are homogeneous. 2) 'Changes in climate forcing through time invalidate such statistical relationships'. Here the reviewer's concern is completely wrong as he/she intimates because 'year to year variability is much greater than long-term climate change'. It is not just greater is at least one order of magnitude greater, maybe more. The regression-type relationships derived in the paper are almost entirely based on high-frequency relationships. Longer timescale variability is relatively small in this regard. Longer timescale change over the 1675-present is not that great anyway (the 1730s for example are only slightly cooler than the 1980s). Global average sea level pressure can't change but patterns will change in different periods and it is these that influence the surface temperature and precipitation patterns. The drawback of using surface temperature and precipitation patterns to reconstruct circulation indices is that you can't then go and look at changes in circulation/surface climate relationships as these have been used in the reconstructions. However, using methods like this produces far more reliable reconstructions than proxy data (trees, ice cores etc) as we can derive indices on a monthly basis and not just for a season or year. (By the way proxy data reconstructions of circulation indices suffer the same problems as it is temperature and precipitation and not the circulation that alters tree ring widths/densities and ice core composition). With the earlier paper from the same EU project (Jones et al, IJC 19, 347-364), pressure reconstructions were derived from station pressure data, so here from 1780 we will be able to look at the change in the strength of circulation/ surface climate relationships through time (I'm doing this in another paper). Finally, and I didn't mean to get into all this detail, but it seemed to just flow, the reconstruction technique does use gradients and not just the station data. The canonical correlation technique relates PC-based patterns of real cirulation data to PC-based patterns of station temperature and precipitation and one pressure site at Paris. The regression relationships are based on the patterns, hence gradients are used implicitly. In conclusion, I'm hoping you will reverse your decision and allow us to resubmit a slightly revised, and reduced in size ( it was too long) paper and send it out to reviewers who will respond in a reasonable time frame. The problems raised by the reviewer are no problems and we can easily address them. They don't invalidate the results. Cheers Phil 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 ----------------------------------------------------------------------------