Contrasting Detection and Attribution of Temperature and Precipitation Changes in the Western Mediterranean from CMIP6 DAMIP Experiments

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Abstract. The Western Mediterranean (WM) is a recognised climate change hotspot where regional temperature and precipitation trends reflect the interplay between anthropogenic forcing and strong internal variability. In this study, the detection and attribution of seasonal temperature and precipitation changes during 1951–2020 across climatically derived subregions of the WM is investigated using a multi-method framework and CMIP6 DAMIP single-forcing experiments. Prior to attribution, models were evaluated according to their ability to reproduce the observed spatial structure of regional trends, and a performance-based subset was selected for the analysis. Detection and attribution were assessed using complementary approaches including the signal-to-noise ratio (SNR), the fraction of attributable risk (FAR), distribution-based comparisons, and an optimal fingerprinting additive decomposition framework. Results reveal a robust anthropogenic imprint on temperature trends across the WM. Forced temperature signals emerge clearly from internal variability in all subregions, with FAR values exceeding 0.95 in most cases. Greenhouse gas forcing is identified as the dominant driver of the observed warming, especially in summer, while anthropogenic aerosols exert a compensating cooling influence that partially offsets it. In contrast, precipitation trends remain largely within the bounds of internal variability. None of the detection approaches identify a robust externally forced precipitation signal at the regional scale, and attribution results suggest that internal variability remains the primary driver of observed precipitation changes during the study period. These findings highlight the importance of subregional-scale attribution and model performance filtering in reducing uncertainties, providing a basis for future attribution studies in this highly vulnerable region.

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