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The intensity and frequency of heavy snowfall events in the Pyrenees were simulated using data from the HIRHAM regional climate model for a control period (1960-1990) and two greenhouse emission scenarios (SRES B2 and A2) for the end of the twenty-first century (2070-2100). Comparisons between future and control simulations enabled a quantification of the expected change in the intensity and frequency of these events at elevations of 1,000, 1,500, 2,000 and 2,500 m a.s.l. The projected changes in heavy snowfall depended largely on the elevation and the greenhouse gas emission scenario considered. At 1,000 m a.s.l., a marked decrease in the frequency and intensity of heavy snowfall events was projected with the B2 and A2 scenarios. At 1,500 m a.s.l., a decrease in the frequency and intensity is only expected under the higher greenhouse gas emission scenario (A2). Above 2,000 m a.s.l., no change or heavier snowfalls are expected under both emission scenarios. Large spatial variability in the impacts of climate change on heavy snowfall events was found across the study area. [ABSTRACT FROM AUTHOR]

Summary: In this study, snowpack series are modeled across the Pyrenees using data derived from the HIRHAM Regional Climate Model for both the control period (1960–1990) and two emission scenarios (SRES B2 and A2) by the end of the 21st century (2070–2100). A comparison of future and control simulations enables us to quantify the expected change in snowpack for the next century. Snow simulations are performed on 20 Regional Climate Model (RCM) grid points over the Pyrenees, covering the entire north–south and east–west transects; data were downscaled for four different altitudinal levels (1500, 2000, 2500, and 3000ma.s.l.). This procedure yields a relatively complete picture of the expected impacts of climate change in the Pyrenees, covering horizontal spatial variability as well as altitudinal gradients. According to the HIRHAM model projections following different greenhouse gas emission scenarios, the thickness and duration of snowpack in the Pyrenees will decrease dramatically over the next century, especially in the central and eastern sectors of the Spanish Pyrenees. The magnitude of these impacts will follow a marked altitudinal gradient: the maximum accumulated snow water equivalent may decrease by up to 78%, and the season with snow cover may be reduced by up to 70% at 1500ma.s.l. The magnitude of the impacts decreases rapidly with increasing altitude; snowpack characteristics will remain largely similar in the highest sectors. The decline of the snowpack would be reduced by half if a medium–low emission scenario was considered (B2) instead of the medium–high concentrations of greenhouse gas assumed in the A2 scenario. [Copyright &y& Elsevier]

Abstract: Previous research has identified the North Atlantic Oscillation (NAO) as one of the dominant atmospheric patterns on the temporal evolution of precipitation and temperature in the Mediterranean area. The NAO is seen to markedly affect snowpack variability and water resource availability in many mountain areas. This study investigated the influence of the NAO on winter precipitation and temperature variability, and on the occurrence of four winter climate modes defined on the basis of combined precipitation and temperature quantiles: warm and wet (WW), warm and dry (WD), cold and wet (CW) and cold and dry (CD). It is known that the occurrence of different winter modes is closely related to snow accumulation in mountains. The present study focused on 15 mountain areas in Mediterranean Europe, Morocco, Turkey and Lebanon. Global circulation models (GCMs) have been used to simulate the relationships between the NAO and winter modes for the next century under a moderate (A1B) greenhouse gas emissions scenario. The results show that for the majority of the mountain areas in the Mediterranean region, the occurrence of different winter modes was closely related to the NAO state, although the relationships were weaker in the easternmost part of the Mediterranean basin. GCMs have accurately simulated the observed relationships, and indicate that the NAO will continue to influence the occurrence of combined precipitation and temperature modes in coming decades. The GCMs also suggest enhanced winter NAOs in the future, which could lead to an increase in the frequency of dry modes. Moreover, as the simulations indicate a steady increase in temperature, winters classified as “cold” in the 21st century will be noticeably rarer compared with recent decades. The relationships between the NAO and snowpack may also change substantially in the future, especially in low altitude areas. [Copyright &y& Elsevier]