4 Introduction The burning of fossil fuels and large scale land use changes in the last 150 years are majorly responsible for emitting large amounts of greenhouse gases. The resulting change in the composition of the atmosphere has had a strong influence on the climate system. Since the beginning of industrialization (e.g. IPCC, 2013), carbon dioxide has increased from 270 parts per million (ppm) to 396 ppm (2013) – a level that is unprecedented for at least the last 800.000 years (IPCC, 2013). The intensified greenhouse effect traps more energy in earth’s atmosphere, which, beside other effects, leads to global warming. The observed warming in the climate system is unequivocal (IPCC, 2013) and so far the global mean of Earth’s atmospheric near surface temperature has warmed up by roughly 0.8 degrees. The year 2016 was reported to be the warmest year in reported weather records since 1880 (NOAA, NASA, 2016). Besides a further temperature increase, the scientific community expects an ongoing increase in sea level rise (SLR), changes in precipitation (both in amounts and patterns) and changes in occurrence rates of extreme weather events (EWEs) (e.g. heat waves, heavy rain events, tropical storms…). A challenge in understanding climate change and measuring the ongoing changes in climate variables (e.g. temperature and precipitation) is the awareness of natural climate variability and how it affects natural weather events. It is important to take into account that climate change and the corresponding natural and socioeconomic impacts will not happen homogeneously in the different regions of the world. Some regions may face an increase in precipitation (i.e. higher northern latitudes). For others, scientists anticipate a decrease (southern Europe, Middle East). As already ongoing climate change becomes more obvious, discussions about the issue will increase as it saturates into institutions, society and efforts to tackle the problems. Besides trying to mitigate (lower carbon emissions to decrease upcoming climate change), there is recognition that adaptation to climate change is also necessary. One central aim of climate science is the provision of information regarding the climate of the future. To obtain this information, so-called General Circulation Models (GCMs) are used. GCMs are numerical models, which aim to represent the physical processes in the atmosphere, ocean, cryosphere and land surface. They are used to simulate the response of the climate system to growing concentrations of greenhouse gases in the atmosphere. To model the future climate, the input of the greenhouse gas concentrations of the future is necessary. But these concentrations completely depend on human behavior, technical advancements, and political decisions in the near future. Since this is not possible to forecast, climate science uses so-called scenarios for greenhouse gas concentration in the atmosphere of the future. These scenarios are indirect scenarios for the development of human society. In the third and fourth assessment report of the IPCC, so-called SRES scenarios (Special Report on Emissions Scenarios) of future emissions and concentrations of greenhouse gases (GHG) in the atmosphere were used as a basis for global climate models. In the latest report (AR5), this changed to the Representative Concentration Pathways (RCPs), which directly are keyed to a range of trajectories of GHG concentrations and climate forcing. They are labeled by their approximate radiative forcing that is reached during or near the end of the 21st century (RCP2.6, RCP4.5, RCP6.0, and RCP8.5) (Burkett, 2014). The RCP2.6 scenario represents a very optimistic scenario with low 4

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