Rare spells of extreme rainfall that would overwhelm today’s flood-defence infrastructure look set to become markedly more frequent in the United States as the climate changes.
Because a warmer atmosphere holds more moisture, episodes of extreme rainfall will increase overall as the world warms. To provide meaningful information about future flood risks, Benjamin Sanderson at the European Centre for Research and Advanced Training in Scientific Computing in Toulouse, France, and his colleagues divided the contiguous United States into 15 regions on the basis of precipitation patterns. For each region, the researchers modelled the probability of record-breaking three-day rainfall events for various climate scenarios.
The simulations suggest that 1000-year rainfalls — extreme events with a 1-in-1000 chance of happening in any given year — will become 2–5 times more frequent if the global temperature reaches 2°C above pre-industrial levels. With 4°C of warming, the models predict that such deluges will be up to 10 times more frequent.
New England, the Southern Great Plains and parts of the Rocky Mountains are among the US regions most at risk, the team found.
Correction: an earlier version of this article gave the wrong journal name for the reference.