The Changing Seasonality of Extreme Daily Precipitation

Global warming is known to substantially increase extreme daily precipitation, but there has been little focus on changes to the seasonal timing of these extreme events. We investigate this question using global and regional climate models from the Coupled Model Intercomparison Project phase 5 and the Coordinated Regional Downscaling Experiment, in 1871-1900, 1976-2005, and 2071-2100 for an extreme future emission scenario (Representative Concentration Pathways, 8.5 W/m(2)). Models reproduce the observed seasonal timing and indicate very little seasonality changes during the past hundred years. However, by the end of the 21st century, extreme precipitation could substantially shift later in the year, in most regions from summer and early fall toward fall and winter. This projected shift is not regionally homogeneous, and, among analyzed regions, is strongest in Northern Europe and Northeastern America (+12 and +17 days, respectively), although local changes of more than a month are also possible. Plain Language Summary The intensification of extreme precipitation is a well-known consequence of global warming, which could have devastating consequences on human societies and the environment. Using global and regional climate models simulations from the end of the nineteenth century to the end of the 21st century, we show that extreme future climate change could also change the seasonal timing of these extreme precipitation events. Models indicate that extreme precipitation could occur later in the year in a warmer climate, shifting in most regions from summer and early fall toward fall and winter. However, the magnitude of this change could also vary strongly between different regions. On the one hand, models indicate little change in Asia, Oceania, and the Tropics. On the other hand, Europe, Africa, South America, and high latitudes could show substantial changes. Among analyzed regions, these changes are particularly strong in Northern Europe and in Northeastern America (+12 and +17 days, respectively), but locally, the timing of extreme daily precipitation could shift by more than a month compared to present-day conditions.