From	Phil Jones	Date	Wed Aug 10 17:13:37 2005
To	Kevin Trenberth
Subject	Re:
Fine with me. Let's hope they agree by tomorrow. Phil At 17:11 10/08/2005, you wrote: Ok so here is how it now reads: The temperature increases are consistent with the observed nearly worldwide reduction in glacier and ice cap mass and extent in the 20^th century. Tropical glacier changes in South America and Africa, and those in Tibet are synchronous with higher latitude ones, and all have shown declines in recent decades. 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). Glaciers and ice caps respond not only to temperatures but also changes in precipitation, and both global mean winter accumulation and summer melting have increased over the last half century in association with temperature increases. Other factors in recent ablation include changes in cloudiness and water vapour and associated radiation, and surface sensible heat exchange. Precipitation anomalies are also important before 1900 in glacier fluctuations. 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) even as enhanced ablation has led to marked declines in mass balances in Alaska and Patagonia. Kevin Phil Jones wrote: Sort of arguing that way. It is also the before 1900 part. Precip and temp anomalies are important at all times for glaciers. Their influence didn't change around 1900. So what about Precipitation anomalies are also important before 1900. I'd not got the implication. Adding also makes it clearer. Phil At 16:56 10/08/2005, Kevin Trenberth wrote: Phil is arguing for changes to 4.5. Maybe the statement is too strong although it is consistent with the last para of 4.5.2.? An alternative might be: Precipitation anomalies are important before 1900. In the context this implies in addition to temperature. Kevin Phil Jones wrote: Georg, I've now also looked at the figures you sent from Ch 4. Kevin has the sentence, which Peter may have added? I reckon this is too strong. Can we omit it? Sentence is Before 1900, glacier fluctuations probably mainly reflect precipitation anomalies. Reasoning Is this a general statement. I wonder if we need it. Oerlemans uses estimated glacier termini positions (and related ELA changes) to infer past temperatures and you have his figure. I know he assumes precip to have remained essentially the same but he backs out temperature. Also glaciers in Europe advanced in the 17th and 18th centuries. It was cooler then (more so in winter than summer). I also have a paper resubmitted to JGR where Alpine precip shows no long-term changes since 1800. This uses loads of stations and is from the ALP-IMP project that ZAMG co-ordinate (Reinhard Boehm). So the advances are caused by more precip, but the retreats by higher summer T and maybe less winter precip. Cheers Phil At 16:23 10/08/2005, Kevin Trenberth wrote: Hi Georg Many thanks for the attachments. I had looked at the ZOD but this is much more informative. Based on your comments and the 4.5 section I have come up with the following bullet. Note that here we are writing for a general audience. I have now tried to include more clearly the factors involved. I think these are consistent with your chapter but the language in your chapter might be improved in a couple of places. For instance an important forcing is radiation (solar and IR) which are greatly impacted by clouds, water vapor, and albedo (the dirty cover on top of snow Phil referred to), and I thought these could be brought out better in your chapter. These are perhaps more basic that temperature lapse rates and precipitation gradients which are consequences. In 4.5.2 you use the term "radiatively forced" but it is not clear what that means. I suggest using some of these terms. Also it is not clear what "amplified hydrological cycle" means. [FYI, the expectation is for more intense precipitation, not necessarily for more total (owing to pollution effects). The former is determined by increased water vapor]. I took some of your words in the following. We need to emphasize that glaciers are not just high latitudes. I retained Kilimanjaro as that has received a lot of publicity. Some of this is necessarily abrupt, but there will be a reference to 4.5 immediately following this bullet. So the recent reversals in NZ and Norway can not be dealt with here. Let me know if you have further suggestions. Again, many thanks Regards Kevin o The temperature increases are consistent with the observed nearly worldwide reduction in glacier and ice cap mass and extent in the 20^th century. Tropical glacier changes in South America and Africa, and those in Tibet are synchronous with higher latitude ones, and all have shown declines in recent decades. 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). Glaciers and ice caps respond not only to temperatures but also changes in precipitation, and both global mean winter accumulation and summer melting have increased over the last half century in association with temperature increases. Other factors in recent ablation include changes in cloudiness and water vapour and associated radiation, and surface sensible heat exchange. Before 1900, glacier fluctuations probably mainly reflect 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) even as enhanced ablation has led to marked declines in mass balances in Alaska and Patagonia. Georg Kaser wrote: Kevin, Have many thanks for compiling and editing 3.9. I agree that the "radiatively forced" and the "amplified hydrological cycle" should be removed and I also agree with Phil's comment on the "local heat budget". In glaciology, the sum of each energy flux toward and from the respective snow/ice surface is considered to make up the "local heat budget". This also includes the sensible heat flux. There are some other points in the text which I would like to comment: 1. Tropical glaciers are considered those in the South American Andes between Venezuela and Norhern Boliva, those in East Africa and those in Irian Jaya (New Guinea). In Chapter 4, Tibetean glaiers are taken as part of the Asian High Mountains (find the present state Chapter 4.5. "Glaciers and Ice Caps attached). 2. Alaska, Patagonia, Karakoram, Norway and NZ cannot be merged in the respective statement. In Alaska and Patagonia, moderately increase accumulation is accompanied by strongly enhanced ablation making the mass balances markedly negative. From glaciological site, no studies concerning atmospheric circulation patterns are provided in the respective studies. In the Karakoram mountains, enhanced accumulation has led to considerable glacier advances, increased winter accumulation from the Westerlies is only suggested but not subject of detailed studies. Heavy debris loads on the tongues probably prevent from enhanced abaltion. In Southwest Norway and NZ South Island, glaciers advances have ceded around 2000. I don't know whether their advances shall still be mentioned in extension; I would not do so beyond the respective statement in Ch. 4.5. 3. "If continued, some may disappear within the next 30 years." This sentence can stand for every mountain region in the world and should not be used for tropical mountains only. Everywhere, many small glaciers have disappeared since the 19th Century maxima and many will disappear soon in the Alps, the Caucasus, in the Asian High mountains etc. as well as in the Tropics. From the today's perspective Mount Kenya, all Mountains in the Rwenzori Range except Mt. Stanley, Irain Jaya will be without glaciers soon, probably sooner than Kilimanjaro; well known and studied glaciers in the Andes like Chacaltaya, Charquini and Pastoruri will also disappear soon. This is not because of a particular regional climate feature but just because they were already small when retreats started. As you will see from Figure 4.5.5. Kilimanjaro's plateau ice is particular, slope glaciers are less. The plateau glaciers retreat from their vertical walls where no accumulation is possible and since they do so, there is no way to find an equilibrium besides disappearance. The vertical walls are a result of cold temperatures high sublimation and strong solar radiance. There is no way to replace the retreat by ice dynamics on the flat summit plateau. Slope glaciers are only partially subject of this kind of ablation and their retreat rate seems to have slowed markedly (See insert of Fig 4.5.5). If Kilimanjaro is mentioned in 3.9. it must also be added that it is a particular case with complex relation to climate change. 4. All studies which investigate tropical glacier retreat and climate show the dominance of changes in energy and mass balance terms which are related to the atmospheric moisture content rather than locally measured air temperatures. Both increased and reduced moisture can lead to negative mass balances and it has done so in most cases studied (Cordillera Blanca, Peru, Cordillera Real, Bolivia, Antisana, Ecuador, Rwenzori, Mt. Kenia, Kilimanjaro). Yet, wherever respective analyses were made, correlations were found to anomalies in ENSO or Indian Oceans Indian Ocean Dipole Mode respectively strongly indicating global warming as the principle reason of th eretreat. I give you this lengthy explanation in order to make sure that the very compressed and condensed bullet in 3.9. gets the right content. I have started to change your paragraph suggestion accordingly but have to admit that, not being a native speaker myself, it either becomes very long or very awkward. I also appreciate Phil's statement about Quelccaya and Sajama. Doug Hardy and Ray Bradley run AWS' there since a couple of years as well as on Kilimanjaro with all the problems of recording data at such high elevation sites. Doug is preparing a paper on the climate records there but it has still not reached it's final state. Information on sublimation on Quelccaya is not published such as the positive mass balances and advances on several Andean glaciers between 1998 and 2002 are not published. Kilimanjaro has experienced both ablation as well as accumulation layers on the horizontal surfaces over the last years. I have just come back from fieldwork there last week and the last half year was a mass loss year. Being very much involved into tropical glaciers myself, I have to accept that such detailed information would be available for several hundreds of glaciers in the world each one providing 10 or more publications. Going into such details cannot be the aim of the report, I am afraid. Best wishes, Georg Georg Kaser ------------------------------------------------- Institut fuer Geographie Innrain 52 A-6020 INNSBRUCK Tel: ++43 512 507 5407 Fax: ++43 512 507 2895 [1]http://meteo9.uibk.ac.at/IceClim/CRYO/cryo_a.html -- **************** Kevin E. Trenberth e-mail: [2]trenbert@ucar.edu Climate Analysis Section, NCAR [3]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 [4]p.jones@uea.ac.uk NR4 7TJ UK ---------------------------------------------------------------------------- -- **************** Kevin E. Trenberth e-mail: [5]trenbert@ucar.edu Climate Analysis Section, NCAR [6]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 [7]p.jones@uea.ac.uk NR4 7TJ UK ---------------------------------------------------------------------------- -- **************** Kevin E. Trenberth e-mail: [8]trenbert@ucar.edu Climate Analysis Section, NCAR [9]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. http://meteo9.uibk.ac.at/IceClim/CRYO/cryo_a.html 2. mailto:trenbert@ucar.edu 3. http://www.cgd.ucar.edu/cas/ 4. mailto:p.jones@uea.ac.uk 5. mailto:trenbert@ucar.edu 6. http://www.cgd.ucar.edu/cas/ 7. mailto:p.jones@uea.ac.uk 8. mailto:trenbert@ucar.edu 9. http://www.cgd.ucar.edu/cas/