Abstract
In the latest IPCC report, worst case scenarios of climate change describe average global surface warming of up to 6°C from pre-industrial times by the year 2100. This study high- lights the influence of a high-end 6 degree climate change on the hydrology of a catchment in central Denmark. A simulation from the global climate model, EC-Earth, is downscaled using the regional climate model HIRHAM5. A simple bias correction is applied for daily reference evapo- transpiration and temperature, while distribution-based scaling is used for daily precipitation data. Both the 6 degree emission scenario and the less extreme RCP4.5 emission scenario are eval- uated for the future period 2071−2099. The downscaled climate variables are applied to a fully dis- tributed, physically based, coupled surface−subsurface hydrological model based on the MIKE SHE model code. The impacts on soil moisture dynamics and evapotranspiration show increasing drying-out tendencies for the future, most pronounced in the 6 degree scenario. Stream discharge and groundwater levels also show increased drying due to higher evapotranspiration. By compar- ing the 6 degree scenario with other emission scenarios, it is found that the most prominent changes in the water balance are caused by drying out of soils rather than precipitation effects.
Highlights
During the last decade the number of hydrological impact studies has been increasing, and several studies have been published trying to quantify future hydrological changes using climate model outputs on both global (e.g. Arnell 1999), national (e.g. Bergstrom et al 2001), and regional scales
The need for ensemble approaches in climate change impact studies has been highlighted several times (e.g. Déqué et al 2007) to encompass more of the uncertainties arising from emission scenarios as well as climate models and downscaling techniques
The high-end scenario was compared with a medium emission scenario, the RCP4.5, from the same general circulation model/regional climate model (GCM/RCM) model combination, and to some degree with results from A1B scenario runs with multiple GCM/RCM combinations
Summary
During the last decade the number of hydrological impact studies has been increasing, and several studies have been published trying to quantify future hydrological changes using climate model outputs on both global (e.g. Arnell 1999), national (e.g. Bergstrom et al 2001), and regional (e.g. van Roosmalen et al 2007) scales. The need for ensemble approaches in climate change impact studies has been highlighted several times (e.g. Déqué et al 2007) to encompass more of the uncertainties arising from emission scenarios as well as climate models and downscaling techniques. The most recent IPCC report (Collins et al 2013) describes the possibility for high-end scenarios like RCP8.5 with a global climate warming of over 4°C at the end of the 21st century. Changes in this range will have profound effects on hydrology and vegetation, with a potential for increasing in large ecological and economic impacts such as water shortage, wildlife loss, crop failure, flooding, and droughts. The hydrology of a high-end scenario has not yet been documented.
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