date: Mon Jan 12 09:09:11 2004 from: Phil Jones subject: Re: Temperature reconstruction for the last millenium to: Jorge Sánchez Sesma Dear Jorge, I addition to the comments I sent last week about people's preconceptions of the MWP and to a lesser extent the LIA, here are a few more on the paper. 1. Greenland isn't inhospitable now nor in the 10th/11th centuries. The Inuit were there the whole time. Inhospitable to Europeans maybe, not to humans in general. 2. The Goudie (1992) reference to trees growing north of where they do now in the 10-12th centuries needs to realise that trees will live happily north of where they are for the rest of their lives provided they have reached a certain size. In other words the warmth they needed only applies to a 30 year period when they germinated. 3. Vineyards were still here in England during the 17th century - see below. They are here now - 7 times more than in 1086. 4. It is best to see what the data says rather than put forward pre-conceptions. I suspect you have more faith in ECS than MBH because it is more in line with what you expect. 5. Up to p4 in your paper, the only data that have been calibrated against instrumental data is the MBH series. All others are anecdotal. 6. ECS is calibrated also, but against MBH - not against the instrumental data ! So, you can't say that MBH is wrong then use a data series developed by calibration against it. The reason for the differences between MBH and ECS has been discussed in the literature. ECS is more likely to be summer responsive and the sites are in mid-to-high latitudes compared to MBH. I'm attaching a paper that you might find relevant. It relates to possible changes in the seasonal cycle. 7. The main problem with the paper, though, is that the ice-core acidity series you use is a forcing series (i.e indicative of volcanic activity) and not a response series (i.e temperature in its simplest form). Your calibration is based on a low-frequency relationship. There will be few degrees of freedom after the smoothing. 8. MRBHK have done a lot more to the borehole record than Huang et al (2000) like. Also it too is calibrated against MBH. It isn't just an interpolation of the original data. 9. You can't choose ECS just because it has more variability than MBH. 10. Finally, just because a warming began 400 years ago doesn't mean that it is all due to the same cause. It was obviously natural until the 20th century, but this doesn't preclude it being human-induced during the last century. One small point, on p3 line 7 of the first para of Background, sea should be sea ice. It took me a while to realise what you must mean here. Cheers Phil Dear Jorge, I will look through the paper when I am away from CRU either next week or the week after. I see you mention vineyards as far north as York in the MWP. This has very little to do with climate change - there is a vineyard near there today. Here is some text I wrote a while ago about two anecdotes, the Thames freezing and vines in York. 1) River Thames freeze-overs (and sometimes frost fairs) only occurred 22 times between 1408 and 1814 [Lamb, 1977] when the old London Bridge constricted flow through its multiple piers and restricted the tide with a weir. After the Bridge was replaced in the 1830s the tide came further upstream and freezes no longer occurred, despite a number of exceptionally cold winters. 1962/3, for example, was the third coldest in the Central England Temperature (CET) record [the longest instrumental record anywhere in the world extending back to 1659, Manley, 1974; Parker et al., 1992], yet the river only froze upstream of the present tidal limit at Teddington. The CET record clearly indicates that Thames (London) 'frost fairs' provide a biased account of British climate changes (let alone larger-scale changes, see Figure 2c) in past centuries. 2) Monks in Medieval England grew vines as wine was required for the sacrament. With careful husbandry vines can be grown today and indeed vineyards are found as far north as southern Yorkshire. There are a considerably greater number of active vineyards in England and Wales today (roughly 350) than recorded during Medieval times (52 in the Domesday Book of AD 1086), exposing as distinctly curious the claims sometimes made that evidence of vine growing in Medieval England provides evidence of unusual warmth at that time. Vine growing persisted in England throughout the millennium. The process of making sparkling wine was developed in London (by Christopher Merret) in the 17th century, fully 30 years before it began in the Champagne region of France. Thus, the oft-cited example of past vine growing in England thus reflects little, if any, on the relative climate changes in the region since Medieval times. Also, vine growing was mainly at monasteries. Because the Romans and the Normans came from the south they brought vines with them. The population that was here at the time of the invasions were Celts when the Romans came and Anglo-Saxons and Celts when the Normans came. Neither of these two peoples drank wine and this is also a factor in why vine growing was never popular. Most of the above comes from the web site of the English vine growing association. Vineyards have produced wine throughout the millennium. As most of the monasteries were destroyed by Henry the 8th in 16th century most of the vineyards fell into disrepair. There were vineyards around London in the 17th century. Cheers Phil At 15:36 05/01/2004 -0600, you wrote: Dear Dr Jones: You will find attached a very crude draft of a paper about Global Temperature reconstruction. This reconstruction have a notable coincidence with recent publication (Esper, Cook and Shweingruber 2002). I would like to know your oppinion and suggestions to improve the text before to be sent this paper to Science. I would like to emphasize that I continue to be interested to visit CRU and stablish a formal collaboration in this subject. My best regards, Jorge Sánchez-Sesma Instituto Mexicano de Tecnología del Agua Subcoordinación de Hidrometeorología Paseo Cuauhnahuac No. 8532, Col. Progreso Jiutepec, Morelos 62550, México telefono: 52+(777)329-3600 x 879 fax 52+(777)3293683 email: jsanchez@tlaloc.imta.mx pagina: [1]http://nimbus.imta.mx 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 ----------------------------------------------------------------------------