[1] High-elevation tropical mountain regions may be more strongly affected by future climate change than their surrounding lowlands. In the tropical Andes a significant increase in temperature and changes in precipitation patterns will likely affect size and distribution of glaciers and wetlands, ecosystem integrity, and water availability for human consumption, irrigation, and power production. However, detailed projections of future climate change in the tropical Andes are not yet available. Here we present first results for the end of the 21st century (2071-2100) using a regional climate model (RCM) based on two different emission scenarios (A2 and B2). The model adequately simulates the spatiotemporal variability of precipitation and temperature but displays a cool and wet bias, in particular along the eastern Andean slope during the wet season, DecemberFebruary. Projections of changes in the 21st century indicate significant warming in the tropical Andes, which is enhanced at higher elevations and further amplified in the middle and upper troposphere. Temperature changes are spatially similar in both scenarios, but the amplitude is significantly higher in RCM-A2. The RCM-A2 scenario also shows a significant increase in interannual temperature variability, while it remains almost unchanged in RCM-B2 when compared to a 20th century control run. Changes in precipitation are spatially much less coherent, with both regions of increased and decreased precipitation across the Andes. These results provide a first attempt at quantifying future climate change in the tropical Andes and could serve as input for impact models to simulate anticipated changes in Andean glaciation, hydrology, and ecosystem integrity.Citation: Urrutia, R., and M. Vuille (2009), Climate change projections for the tropical Andes using a regional climate model: Temperature and precipitation simulations for the end of the 21st century,

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We statistically reconstruct austral summer (winter) surface air temperature fields back to AD 900 (1706) using 22 (20) annually resolved predictors from natural and human archives from southern South America (SSA). This represents the first regional-scale climate field reconstruction for parts of the Southern Hemisphere at this high temporal resolution. We apply three different reconstruction techniques: multivariate principal component regression, composite plus scaling, and regularized expectation maximization. There is generally good Electronic supplementary material The online version of this article

Abstract. Climate change is expected to have a large impact on water resources worldwide. A major problem in assessing the potential impact of a changing climate on these resources is the difference in spatial scale between available climate change projections and water resources management. Regional climate models (RCMs) are often used for the spatial disaggregation of the outputs of global circulation models. However, RCMs are time-intensive to run and typically only a small number of model runs is available for a certain region of interest. This paper investigates the value of the improved representation of local climate processes by a regional climate model for water resources management in the tropical Andes of Ecuador. This region has a complex hydrology and its water resources are under pressure. Compared to the IPCC AR4 model ensemble, the regional climate model PRECIS does indeed capture local gradients better than global models, but locally the model is prone to large discrepancies between observed and modelled precipitation. It is concluded that a further increase in resolution is necessary to represent local gradients properly. Furthermore, to assess the uncertainty in downscaling, an ensemble of regional climate models should be implemented. Finally, translating the climate variables to streamflow using a hydrological model constitutes a smaller but not negligible source of uncertainty.

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The Puelo River is a watershed shared between Chile and Argentina with a mean annual streamflow of 644 m 3 s −1 . It has a high ecologic and economic importance, including introduced farmed salmon, tourism, sports fishing and projected hydroelectricity. Using Austrocedrus chilensis and Pilgerodendron uviferum tree-ring records we reconstructed summer-fall (December-May) Puelo River streamflow, which is the first of such reconstructions developed in the Pacific domain of South America. The reconstruction goes back to 1599 and has an adjusted r 2 of 0.42. Spectral analysis of the reconstructed streamflow shows a dominant 84-year cycle which explains 25.1% of the total temporal variability. The Puelo River summer-fall streamflow shows a significant correlation (P>0.95, 1943-2002) with hydrological records throughout a vast geographic range within the Valdivian eco-region (35 to 46°S). Seasonal Puelo River interannual streamflow variability is related to large-scale oceanic and atmospheric circulation features. Summer-fall streamflows showed a significant negative correlation with the Antarctic Oscillation (AAO), whereas winter-spring anomalies appear to be positively connected with sea surface temperature variations in the tropical Pacific. In general, above-and below-average discharges in winterspring are related to El Niño and La Niña events, respectively. The temporal patterns of the observed and reconstructed records of the Puelo River streamflow show a general decreasing trend in the 1943-1999 period. Projected circulation changes for the next decades in the Southern Hemisphere would decrease summer-fall Puelo River streamflows with significant impacts on salmon production, tourism and hydropower generation.

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Because of the reported decreasing trends in precipitation in south central Chile and the high priority of the Valdivian rain forest ecoregion conservation, it is essential to understand long‐term changes in water availability in this area. Thus, this study presents a 410 year annual streamflow reconstruction for the Maule River watershed located in a Mediterranean‐type climate in the northern part of the ecoregion (35°S–36°30′S). The annual streamflow reconstruction used Austrocedrus chilensis tree ring chronologies, and the adjusted R2 was 0.42. The reconstruction was characterized by interannual, interdecadal, and multidecadal oscillation modes, some of which might be explained by solar and lunar cycles and by ocean‐atmospheric forcings. Temporal correlations between the reconstruction and climatic indices, such as the El Niño–Southern Oscillation and the Antarctic Oscillation, demonstrate that water availability is influenced by tropical and high‐latitude forcings in this area. Extreme low and high streamflows are particularly related to ocean‐atmospheric conditions in the tropical Pacific. The Maule River watershed streamflow reconstruction reveals a higher proportion of streamflows below the mean in the last century compared to the previous three centuries.