Robust Projections of Changing Precipitation Evenness in a Warming Climate

Abstract Global warming is expected to increase global mean precipitation by 2%–4%/K, but this increase may be uneven, leading to more flooding but also droughts. Utilizing the Gini index, a metric frequently used in economics, we analyze the evenness of precipitation distribution locally and globally from daily to annual‐mean timescale in CMIP6 global warming simulations. Spatial evenness of daily precipitation decreases over land and ocean, tropics and extratropics. Changes in temporal evenness of local‐daily precipitation show a complex geographic pattern. However, particularly over land, we show that a simple theoretical scaling explains this complexity to result from increased precipitation intensity scaling at about the Clausius‐Clapeyron rate, and a local balance between changes in annual‐mean precipitation and dry‐day fraction. These results provide a novel perspective on the relation between global constraints on the hydrological cycle to regional precipitation changes independent of changes in the geographic distribution of precipitation.