To: Kevin Trenberth <firstname.lastname@example.org>, Peter Lemke <email@example.com>
Subject: Re: 3.9
Date: Wed Aug 10 10:49:18 2005
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.
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
Are my terms "20th century" and "recent decades" correct?
Peter Lemke wrote:
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.
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 firstname.lastname@example.org