From	Phil Jones	Date	Wed Aug 10 10:49:18 2005
To	Kevin Trenberth, Peter Lemke
Subject	Re: 3.9
Peter, Kevin Not having seen Ch 4, I agree that the term 'local heat budget' can be ambiguous. Are you also discussing the issue of 'dirty' glaciers? For the Alps, the Swiss (well Wilfried Haeberli) reckon that temperature alone cannot explain all the retreat in some recent summers (especially 2003). Would local heat budgets include the effects of local anthropogenic pollutants making the snow less white? Lonnie Thompson has been on Quelccaya in the last couple of months and reports that it is in an awful state. Like Kilimanjaro, the recent annual layers aren't distinguishable. Lonnie reckons a lot of retreat is caused by sublimation. On Quelccaya Lonnie and Ray Bradley have put up an AWS (on Sajama too). They've not got as much data as they hoped as both have fallen over due to melting and also the guide who helped them put one on Quelccaya later went back and brought it back down to try and sell ! I'm happy with Kevin's draft, if local heat budgets is explained in your chapter. Cheers Phil At 17:29 09/08/2005, Kevin Trenberth wrote: Peter, Thanks (sorry I can't get rid of the blue). I am cc'ing Phil on this: Georg has suggested instead the following. The temperature increases are consistent with the observed nearly worldwide reduction in glacier and ice cap mass and extent with strongest recession rates in the 1930s and 1940s and after 1990 and little changes around 1970. Tropical glacier changes are synchronous with global ones, Kilimanjaro being an exception with radiatively forced constant retreat of the plateau ice. 20^th Century glacier retreats are consistent with temperature variations. Before 1900, glacier fluctuations are probably not only reflecting temperature variations but mainly precipitation anomalies. In the Tropics, glacier changes are related to atmospheric moisture variations which, in turn, correlate with sea surface temperatures in the respective source regions and varying atmospheric circulation modes. In some regions (Alaska, Patagonia, Karakoram) moderately increased accumulation is observed indicating an amplified hydrological cycle. I am not altogether happy with this wording. In this bullet it reflects findings from your chapter and ours (wrt precip, temp, circulation etc). I would propose the following as a compromise between the old text and the proposed: The temperature increases are consistent with the observed nearly worldwide reduction in glacier and ice cap mass and extent in the 20th century. Tropical glacier changes in South America, Africa and Tibet are synchronous with global ones, and all have shown declines in recent decades. If continued, some may disappear within the next 30 years. Local temperature records all show a slight warming, but not of the magnitude required to explain the rapid reduction in mass of such glaciers (e.g., on Kilimanjaro), which instead depends on local heat budgets. Glaciers and ice caps respond not only to temperatures but also changes in precipitation, and before 1900, glacier fluctuations are probably not only reflecting temperature variations but mainly precipitation anomalies. In some regions moderately increased accumulation observed in recent decades is consistent with changes in atmospheric circulation and associated increases in winter precipitation (e.g., southwestern Norway, parts of coastal Alaska, Patagonia, Karakoram, and Fjordland of the South Island of New Zealand). Note I have retained a bit more detail on the regions affected, and tried to stay away from "radiatively forced" (whatever that means) and vague terms like "amplified hydrological cycle". I also want to retain more specific reference to the precip and circulation changes going together. Whether "local heat budgets" is adequate is my main question? I gather this is related to changes in cloud and sunshine, increased heating that goes into melting and ablation rather than temp increases. Should we spell that out? Do you deal with that? I also did not add the detail on the dates in first sentence as those should be in your chapter and they don't relate directly to the other variables. Are my terms "20th century" and "recent decades" correct? Thanks Kevin Peter Lemke wrote: Dear Kevin, after his return from the Kilimanjaro Georg has supplied a modification to the text in 3.9 concerning the glaciers. I have made a tiny change further down in the text replacing "order" by "approximately" meaning 1mm/year and not implying, say, 3mm/year. Best regards, Peter -- **************** Kevin E. Trenberth e-mail: [1]trenbert@ucar.edu Climate Analysis Section, NCAR [2]www.cgd.ucar.edu/cas/ P. O. Box 3000, (303) 497 1318 Boulder, CO 80307 (303) 497 1333 (fax) Street address: 1850 Table Mesa Drive, Boulder, CO 80303 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 ---------------------------------------------------------------------------- References 1. mailto:trenbert@ucar.edu 2. http://www.cgd.ucar.edu/cas/