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Mountain ecosystems are commonly regarded as being highly sensitive to global change. Due to the system complexity and multifaceted interacting drivers, however, understanding current responses and predicting future changes in these ecosystems is extremely difficult. We aim to discuss potential effects of global change on mountain ecosystems and give examples of the underlying response mechanisms as they are understood at present. Based on the development of scientific global change research in mountains and its recent structures, we identify future research needs, highlighting the major lack and the importance of integrated studies that implement multi-factor, multi-method, multi-scale, and interdisciplinary research. Zusammenfassung: Gebirgsökosysteme gelten generell als sehr empfindlich gegenüber dem Globalen Wandel. Allerdings sind aufgrund der Komplexität der Systeme und wegen vielfältiger Interaktionen der Einflussfaktoren sowohl das Verständnis gegenwärtiger Reaktionen als auch Vorhersagen zukünftiger Änderungen sehr schwierig. Unser Ziel ist es, potenzielle Effekte des Globalen Wandels auf Gebirgsökosysteme zu diskutieren und Beispiele für die zugrunde liegenden Reaktionsmechanismen zu geben, soweit sie derzeit verstanden sind. Basierend auf der Entwicklung und den heutigen Strukturen der "Global Change"-Forschung in Gebirgen zeigen wir den Forschungsbedarf auf und betonen insbesondere das weitgehende Fehlen und die Bedeutung integrativer Studien über verschiedene Faktoren, Methoden, Maßstäbe und Disziplinen hinweg.

Climate simulations in West Africa have been attributed with large uncertainties. Global climate projections are not consistent with changes in observations at the regional or local level of the Niger basin, making management of hydrological projects in the basin uncertain. This study evaluates the potential of using the quantile mapping bias correction to improve the Coupled Model Intercomparison Project (CMIP5) outputs for use in hydrology impact studies. Rainfall and temperature projections from 8 CMIP5 Global Climate Models (GCM) were bias corrected using the quantile mapping approach. Impacts of climate change was evaluated with bias corrected rainfall, temperature and potential evapotranspiration (PET). The IHACRES hydrological model was adapted to the Niger basin and used to simulate impacts of climate change on discharge under present and future conditions. Bias correction significantly improved the accuracy of rainfall and temperature simulations compared to observations. Nash coefficient (NSE) for monthly rainfall comparisons of 8 GCMs to the observed was improved by bias correction from 0.69 to 0.84. The standard deviations among the 8 GCM rainfall data were significantly reduced from 0.13 to 0.03. Increasing rainfall, temperature, PET and river discharge were projected for all GCMs used in this study under the RCP8.5 scenario. These results will help improving projections and contribute to the development of sustainable climate change adaptation strategies.

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<p>This research compared a set of past projections made by the Intergovernmental Panel on Climate Change (IPCC) to observations originating from both gauged stations and satellite products. Three IPCC assessment reports were taken into account (First, Second and Third assessment reports- FAR, SAR and TAR) and for each, two scenarios from various models were chosen. The period 1998-2005 was considered. A focus was given to West Africa, which was divided in 3 subregions following the latitudes and two main variables for the region were analyzed: precipitation and temperature. The analyses were conducted on mean annual values and monthly annual cycles both at subregional and regional levels. They revealed that the differences are greater on lower latitudes and depend a lot on the scenarios. The Business-as-Usual scenario which assumes that few or no steps are taken to limit greenhouse gas emissions seems to be the one that is the closest to the observations. The relative importance and potential implications of the differences between projections and observations on the society were appreciated with regard to key development sectors in the region such as water, agriculture; health; breeding, fishery. We concluded by giving some recommendations that might be very useful for policy/decision makers but also by listing possible topics for further research that could be addressed by the scientific community.</p><p>Keywords: Climate change; Climate models; Past Projections; Observations; West Africa</p>