RCMGiS: New climate scenarios based on radiative forcing change over the Carpathian Basin

The continuously increasing frequency and intensity of certain extreme events make necessary to prepare for the climate change impacts with special focus on vulnerable sectors and areas. Detailed and quantitative information on climate change is crucial in order to have targeted and sustainable adaptation strategies. The RCMGiS project serve a proper scientific basis for these strategies through provision of meteorological information on climate change to the National Adaptation Geographical Information System (NAGiS).

Regional climate models (RCMs) provide detailed information about the regional climate change. The prototype of NAGIS is based on outputs of 2 RCMs and the RCMGiS project aims at improving these climate data. The most important objectives of the project are as follows:

• To develop the climate model data providing future climate information for NAGiS. New climate simulations will be performed on 10 km horizontal resolution using the recent versions of ALADIN-Climate and RegCM regional climate models adapted at the Hungarian Meteorological Service and at the Eötvös Loránd University, Department of Meteorology, respectively. After sensitivity studies are performed to determine the optimal settings for the subsequent climate simulations, longer historical runs are conducted to test the models’ ability to reconstruct the climatological characteristics of a past period. Model results are validated against a high-quality homogenized data set produced in the framework of the CARPATCLIM project for Hungary.
• To quantify the uncertainties of climate projections. Climate simulations have various uncertainties attributable mainly to the approximate description of the anthropogenic influences and physical processes. In the project, special attention is paid to quantification of simulation uncertainties applying the ensemble technique, i.e., considering a number of model experiments. For the two RCMs, 2 different global climate models prescribe the large-scale features. Furthermore, to account for the potential impacts of human activities, 2 newly presented RCP scenarios are taken: the "pessimistic" RCP8.5 and the "optimistic" RCP4.5. Altogether 2 model runs will be performed using the available 2 RCMs and 2 scenarios, so model uncertainty and scenario uncertainty are simultaneously described. Future changes will be quantified for 2021–2050 and 2071–2100 relative to the reference period of 1971–2000.
• To provide climate model data for impact assessments. RCM outputs are, directly or through special post-processing techniques, providing input parameters for quantitative impact assessments. Impact investigations based on climate model results consider the expected climate change signal with the associated uncertainties and define the appropriate adaptation actions. In Hungary, particularly water supply and management, forestry, environmental sector, disaster management, agriculture, tourism and human health can be significantly affected by climate change. The project plans to involve the experts of these sectors.
• To train and support the users to apply projection results and uncertainty information. In Hungary, (end-)users, decision-makers and general public are not yet fully open to use quantitative meteorological data with probabilistic uncertainty information. The project intends to encourage this approach by workshops and trainings.