CICERO - Senter for klimaforskning

The Changing Seasonality of Extreme Daily Precipitation

Louis Marelle-Sebrechts, Gunnar Myhre, Øivind Hodnebrog, Jana Sillmann, Bjørn Hallvard Samset

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/m2). 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.

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