Widespread shift toward extreme dominated precipitation with pronounced trends in arid and mediterranean regions.

Understanding how precipitation extremes evolve relative to total precipitation has important implications for hydrology, water resources, and climate risk management. While previous studies have assessed trends in total precipitation and extremes separately, the changing balance between them remains underexplored globally. Here, we use the Extreme Precipitation Fraction (EPF)—the ratio of a year’s wettest daily precipitation event to its total annual precipitation—as a physically meaningful metric to quantify the dominance of extremes within annual rainfall totals. Using an ensemble of 25 CMIP6 global climate model simulations from the NASA NEX-GDDP dataset, we examine historical EPF patterns, projected trends under the high-emissions scenario. A first-order relative-change decomposition is then used to quantify the separate contributions of annual maximum daily precipitation and total annual precipitation to EPF trends. Results show that, historically, EPF values are highest in hot and cold deserts, where a single event contributes over 13–15% of annual rainfall, and lowest in tropical rainforest and monsoon zones (< 4%). Projected trends show a global shift toward more extreme-dominated regimes, particularly in dryland and Mediterranean climates. EPF increases exceed + 0.2 per decade in Mediterranean zones, where over 70% of grids show positive trends above + 0.1. In contrast, polar and high-latitude snow-dominated climates exhibit declining EPF values. Attribution of EPF trends to its individual contributions shows that changes in total annual precipitation dominate EPF trends in arid and Mediterranean regions (annual-maximum contribution < 45%), whereas changes in extreme precipitation contribute more strongly in humid temperate and monsoonal regions (> 54%). At high latitudes (> 67.5°N), changes in total precipitation account for more than 70% of EPF trends. These findings reveal that precipitation is increasingly delivered through fewer, more intense events in vulnerable regions, with implications for climate-risk assessment and adaptation planning.