環境：19世紀後半以降、地中海地域の降水量はほぼ安定している

Precipitation in the Mediterranean region has remained stable, despite variation across years and decades, an analysis of historical trends from 1871–2020 finds. The findings, published in Nature, are based on data from 23,000 stations across 27 countries and have important implications for social, economic and environmental policies in the region.

The Mediterranean region is characterized by an uneven distribution of precipitation throughout the year. Climate change projections and observational studies have suggested that precipitation will decrease across the region during the 21st century. However, other research has proposed that precipitation changes are driven by atmospheric circulation patterns, which maintains stability over the long term.

Using data from 23,000 precipitation stations across 27 countries, including France, Italy, Morocco, Egypt and Greece, Sergio Vicente-Serrano and colleagues created a dataset that covers the period 1871–2020, enabling them to investigate annual and seasonal precipitation trends over the long term. They also compared the dataset with modelling from Coupled Model Intercomparison Project (CMIP) 5 and 6. They found that precipitation in the region had largely remained stable over this time period, but did show strong spatial variability and differences between decades and also seasonally. While trends could be identified for some regions and time periods the authors attribute this to atmospheric dynamics and suggest these can be linked to internal variability. They note that their dataset reconciles observations with CMIP 6 modelling of past precipitation, both of which do not indicate a prevailing past precipitation trend in the region.

While they identified negligible precipitation trends over this time period, the authors note that the Mediterranean region is experiencing a period of increasing climatic aridity that is driven by increased atmospheric evaporative demand, which is a result of temperature rises in the region. They conclude that their findings will have important implications for environmental, agriculture and water resource planning in the region.