Downward Mediterranean Cloudiness Beyond Little Ice Age Background Variability

Abstract

Cloudiness–sea interaction substantially influences Earth’s climate by shaping precipitation patterns and radiative budgets. However, our understanding of long-term variations in land-based cloud cover, spanning over decades, centuries, and more, remains limited. This study presents the most extensive reconstruction to date of the annual total cloud cover fraction across the Mediterranean, spanning 1500–2022 CE. A notable shift occurred after 1818, marked by a surge in multidecadal variability and a sustained decline in cloud cover. This change has been attributed to several factors, including the eruption of Mount Tambora in Indonesia in 1815, intensified solar forcing, and a positive phase of the Atlantic Multidecadal Oscillation. These factors collectively reshaped cloudiness beyond typical background variability. By shedding light on the complex interactions with the climate system, our findings suggest that temperature changes may drive increased cloudiness in the Mediterranean when influenced by cold air masses through advection. This emphasizes the need for a deeper exploration of the impact of clouds on regional atmospheric circulation and climate changes. Ultimately, our enhanced understanding of the relationship between cloudiness and climate change provides valuable insights for climate models. While these models consistently project a decrease in cloudiness over the Mediterranean, our findings can also be helpful in understanding cloud variability in other parts of the globe.