ABSTRACT

0519415
Vuille
The tropical Andes are one of the regions of the globe where recent climate change is
most evident, consistent with the notion that high-elevation mountain ranges that extend into the
mid-troposphere will experience greater warming. As a result glaciers are receding throughout the
tropical Andes, with potentially severe consequences for the availability of drinking water, and
water for irrigation, mining and hydropower production.
General Circulation Models (GCMs) run with a 2.CO2 scenario predict an additional
warming of more than 2.5.C by the end of the century. However large uncertainties exist about
these future projections, especially because the coarse resolution of GCMs is inadequate to
resolve the meso- and local-scale circulation features associated with the steep Andean
topography. To accurately understand and predict future climate change and its impact on tropical
Andean glaciers, higher resolution models and a better simulation of variables other than
temperature are required.
We propose to simulate climate variability and change in the Andes under both presentday
conditions (1961-90 and 1958-2001) and two different IPCC-SRES emission scenarios
(2071-2100) with a regional climate model (PRECIS) to gain a better understanding of how
future climate change might affect tropical Andean glaciers.
Results from our regional climate model will be validated with observational data from
space before they are used as input into a glacier-climate model (ITGG 2.0) to simulate how
glacier mass balance will be affected by future climate change. The simulated present-day mass
balance of selected glaciers will be compared with observational records from the tropical Andes
to verify the accuracy of our results. To gain a better understanding of the consequences of
glacier retreat, the ITGG 2.0 model will also be used to simulate changes in runoff from Andean
watersheds. The anticipated results of our proposed research are:
1) The use of a high-resolution model will improve simulations of climate in this area of complex
terrain and yield more accurate predictions of future climate change than are available to date
from GCM.s.
2) An in-depth model validation with observational data will lead to a better assessment of model
performance (for both the RCM and the ITGG 2.0).
3) We will for the first time establish robust projections of how glaciation and runoff will change
in this region at the end of the 21st century. This has important implications for the anticipated
future water shortage in the region and will provide much needed information to implement
adaptation and mitigation strategies.
4) Finally we anticipate a significant model improvement as a result of using regional climate
model data instead of course resolution reanalysis data as input into the ITGG 2.0 model.
We strongly believe that our proposed research addresses a key issue related to future
climate change in the tropical Andes, which is of high scientific interest but also of primary
socio-economic relevance for the region. The potential for a future water crisis is evident and this
water shortage is related to a projected future change in runoff, due to the observed rapid glacier
retreat. The scientific merit of this proposal is therefore to gain a better understanding of both
mechanisms and consequences related to the disappearance of tropical Andean glaciers. This
increased knowledge on how fast and how far glaciers will recede and how much this will affect
future runoff and water availability from the Andes will have a significant and broad impact on
local economies and populations. Without a better and much more detailed knowledge of how
future climate change will affect glaciological and hydrological systems in the Andes, no
mitigation and adaptation strategies can be put in place.

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