Extreme precipitation events, which fall into the 99th percentile of daily events, have increased across the contiguous United States since the 1950s in response to rising temperatures. But despite assertions by the climate community that increasing precipitation extremes inevitably lead to higher flood magnitudes, multiple studies have demonstrated that this has not been the case.
In a recent commentary, Sharma et al. suggest a number of reasons for this dichotomy, in the process highlighting the complex relationship between changes in precipitation and flooding. The authors argue that a number of factors, including less soil moisture at storm onset, shifts in atmospheric circulation that reduce storm durations, smaller snowpacks, and earlier snowmelt, can all decrease the magnitude of floods even when the atmosphere holds more moisture as temperatures warm.
Because a substantial amount of uncertainty remains regarding the connections between changes in precipitation and in floods across a wide range of storm, catchment, and hydrologic conditions, the team asserts that a more collaborative approach between the hydrologic and atmospheric communities is needed to advance our understanding of how floods may change in the future. Given the societal implications, the authors argue that better comprehending this relationship and making it more understandable to the climate community and policy makers should constitute a new grand challenge for the hydrologic community. (Water Resources Research, https://doi.org/10.1029/2018WR023749, 2018)
—Terri Cook, Freelance Writer