Impacts and Consequences of Predicted Climate Change on Andean Glaciation and Runoff

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0519415VuilleThe tropical Andes are one of the regions of the globe where recent climate change ismost evident, consistent with the notion that high-elevation mountain ranges that extend into themid-troposphere will experience greater warming. As a result glaciers are receding throughout thetropical Andes, with potentially severe consequences for the availability of drinking water, andwater for irrigation, mining and hydropower production.General Circulation Models (GCMs) run with a 2.CO2 scenario predict an additionalwarming of more than 2.5.C by the end of the century. However large uncertainties exist aboutthese future projections, especially because the coarse resolution of GCMs is inadequate toresolve the meso- and local-scale circulation features associated with the steep Andeantopography. To accurately understand and predict future climate change and its impact on tropicalAndean glaciers, higher resolution models and a better simulation of variables other thantemperature are required.We propose to simulate climate variability and change in the Andes under both presentdayconditions (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 howfuture climate change might affect tropical Andean glaciers.Results from our regional climate model will be validated with observational data fromspace before they are used as input into a glacier-climate model (ITGG 2.0) to simulate howglacier mass balance will be affected by future climate change. The simulated present-day massbalance of selected glaciers will be compared with observational records from the tropical Andesto verify the accuracy of our results. To gain a better understanding of the consequences ofglacier retreat, the ITGG 2.0 model will also be used to simulate changes in runoff from Andeanwatersheds. 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 complexterrain and yield more accurate predictions of future climate change than are available to datefrom GCM.s.2) An in-depth model validation with observational data will lead to a better assessment of modelperformance (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 changein this region at the end of the 21st century. This has important implications for the anticipatedfuture water shortage in the region and will provide much needed information to implementadaptation and mitigation strategies.4) Finally we anticipate a significant model improvement as a result of using regional climatemodel 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 futureclimate change in the tropical Andes, which is of high scientific interest but also of primarysocio-economic relevance for the region. The potential for a future water crisis is evident and thiswater shortage is related to a projected future change in runoff, due to the observed rapid glacierretreat. The scientific merit of this proposal is therefore to gain a better understanding of bothmechanisms and consequences related to the disappearance of tropical Andean glaciers. Thisincreased knowledge on how fast and how far glaciers will recede and how much this will affectfuture runoff and water availability from the Andes will have a significant and broad impact onlocal economies and populations. Without a better and much more detailed knowledge of howfuture climate change will affect glaciological and hydrological systems in the Andes, nomitigation and adaptation strategies can be put in place.