Human influence on the intensification of extreme precipitation in North America

Increases in extreme precipitation have been identified in the observations in North America and models and theory consistently suggest continued increases with additional warming. Heavy precipitation events can have large impacts and investigating attribution is an important component of understanding the drivers of these events. Increases in extreme precipitation have been attributed to human influence at global and hemispheric scales, and we extend the assessment to continental and smaller scales over North America. We use three large ensembles, two from fully coupled Earth system models (CanESM2, CESM1) and one from a regional climate model (CanRCM4) to investigate annual maximum 1- and 5-day precipitation. Generally consistent results are found across the different models, two different attribution methods, and physical understanding. We show that human influence has contributed to the increasing frequency and severity of extreme precipitation across North America. These increases are expected to continue with further warming.