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A groundbreaking study published in Nature provides new insights into long-term precipitation patterns in the Mediterranean region. Contrary to previous estimates of a declining trend in rainfall, the study finds that Mediterranean precipitation has largely remained stable over the period 1871–2020, despite significant variability across years and decades. The study, which includes contributions by Associate Professor Aristeidis Koutroulis of the School of Chemical and Environmental Engineering at the Technical University of Crete, is based on an extensive dataset comprising measurements from 23,000 stations across 27 countries.

The Mediterranean climate is known for its highly uneven distribution of rainfall throughout the year. While climate change projections and observational studies have suggested that precipitation will decrease across the region during the 21st century, the new study provides a more nuanced understanding. The research team, led by Sergio Vicente-Serrano, analyzed historical precipitation data and compared it with simulations from the Coupled Model Intercomparison Project (CMIP) 5 and 6. Their findings reveal that while precipitation patterns exhibit strong seasonal and spatial variability, a consistent downward trend is not evident. Instead, fluctuations in precipitation appear to be driven primarily by atmospheric circulation patterns and internal climate variability.

While precipitation has remained consistent, the authors highlight that the region is experiencing increased climatic aridity driven by rising temperatures, leading to enhanced evaporation. Prof. Aris Koutroulis emphasized the importance of the study, stating: "This study underscores the power and necessity of robust, open access in situ data. Accurate, long-term ground measurements are critical for untangling the complexities of climate variability and supporting effective management of environmental resources, agriculture, and water resource strategies in the Mediterranean."

The study reconciles historical observations with CMIP 6 modeling of past precipitation, both of which indicate that there is no predominant decreasing trend in Mediterranean rainfall. These insights challenge existing assumptions and provide a more detailed picture of how climate variability, rather than a steady decline in rainfall, may shape future environmental and economic strategies in the region.

The complete study is published in Nature and accessible online: High temporal variability not trend dominates Mediterranean precipitation | Nature