Frequency of extreme precipitation increases extensively with event rareness under global warming

TLDR

Heaviest extreme precipitation intensities rise with global warming, yet the frequency of such events and their combined impact on total extreme rainfall remain poorly understood, despite significant societal implications. The study uses observations and climate model simulations to document strong increases in the frequencies of extreme precipitation events on decadal timescales. Observational records and climate model outputs are analyzed to quantify decadal frequency changes of extreme precipitation. Observations and models show that total precipitation from intense events nearly doubles per degree of warming, mainly due to frequency increases while intensity changes are weak; this shift intensifies with event rarity, implying that the most intense events could almost double in occurrence per degree of further warming, a change far exceeding that of global mean precipitation.

Abstract

The intensity of the heaviest extreme precipitation events is known to increase with global warming. How often such events occur in a warmer world is however less well established, and the combined effect of changes in frequency and intensity on the total amount of rain falling as extreme precipitation is much less explored, in spite of potentially large societal impacts. Here, we employ observations and climate model simulations to document strong increases in the frequencies of extreme precipitation events occurring on decadal timescales. Based on observations we find that the total precipitation from these intense events almost doubles per degree of warming, mainly due to changes in frequency, while the intensity changes are relatively weak, in accordance to previous studies. This shift towards stronger total precipitation from extreme events is seen in observations and climate models, and increases with the strength - and hence the rareness - of the event. Based on these results, we project that if historical trends continue, the most intense precipitation events observed today are likely to almost double in occurrence for each degree of further global warming. Changes to extreme precipitation of this magnitude are dramatically stronger than the more widely communicated changes to global mean precipitation.