Sunday, December 18, 2011

1123708417.txt

From: Phil Jones <p.jones@uea.ac.uk>
To: Kevin Trenberth <trenbert@ucar.edu>
Subject: Re:
Date: Wed Aug 10 17:13:37 2005

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
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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/

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