Assessment of changes in absolute extreme temperatures in the Mediterranean region using ERA5-Land reanalysis data

Abstract

We present the analysis of the spatio-temporal changes in absolute extreme temperatures of the coldest night (TNn), coldest day (TXn), and the hottest night (TNx) and, hottest day (TXx) as defined by the Expert Team on Climate Change Detection and Indices in the Mediterranean Region (MedR) for the period 1950–2023 using ERA5-Land reanalysis gridded dataset. Results show that the annual and seasonal frequencies of TNn and TXn have significantly decreased, while the frequencies of TNx and TXx have increased over the last 74 years in the MedR particularly during hot periods of the year. Since 1950, the magnitude of change in the annual TNn is higher than all absolute extreme temperature indices in the MedR, with more pronounced trends in winter in the western MedR. The hottest year in the MedR since 1950 was 2023, when 35% of the highest absolute maximum temperatures were recorded. According to the results of Pettitt’s test, the most significant change point for MedR was in the late 1980s for the absolute extreme cold temperature indices and in the late 1990s for the absolute extreme warm temperature indices. Spatial differences in warming rates are observed for all absolute extreme temperature indices in the MedR. The increase in temperatures, particularly TXx and TNn, is much more pronounced in Western Mediterranean (WMed) during the annual and summer season than in the eastern Mediterranean (EMed).