Temperature characteristics over the Carpathian Basin-projected changes of climate indices at regional and local scale based on bias-adjusted CORDEX simulations

The present research focuses on temperature change signals over the Carpathian Basin with a special focus on selected lowland and mountainous subregions. High-resolution (0.11 degrees) EURO-and Med-CORDEX regional climate model (RCM) simulations of near-surface air temperature are analysed based on raw and bias-adjusted data. The mini-ensemble consists of eight RCM simulations driven by five different general circulation models for the period 1976-2099 under the high-end RCP8.5 scenario. The high-resolution, homogenized and quality controlled CARPATCLIM was used as a reference dataset. The selected subregions cover eight municipalities located at diverse altitudes: Bratislava, Budapest, Brassov, Debrecen, Hoverla, Novi Sad, P & eacute;cs and Poprad. The following climate indices are assessed: summer days, ice days, frost days, tropical nights, the coldest day, the warmest day, the coldest night and the warmest night. In general, for the reference period (1976-2005) bias adjusted RCM data showed almost perfect match with observations. Accordingly, no best performing RCM is found for all indices. The ensemble mean of the bias-adjusted RCM simulations projects an increase (decrease) of 32% and 112% (18% and 25%) in the annual number of summer days and tropical nights (frost days and ice days) for the period 2021-2050. For 2070-2099 we can expect more frequent tropical nights (about five times) with respect to the reference period and the frequency of frost days can be halved. Profound warming manifests in the increase of the warmest temperature of day of up to 2-3 degrees C by the near future and of 5-7 degrees C by the end of the 21st century, which means the absolute maximum temperature can reach 44-47 degrees C for the period 2070-2099. Our results also highlight the need for bias-adjusted data adapted by different sectors (human health, agriculture, transport, disaster management, heritage conservation) under the national adaptation strategies.