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The past year has seen torrential rains flood parts of the US, from flash flooding in Kentucky last summer to the downpour in Fort Lauderdale, Florida, last week, in which a third of the city鈥檚 annual rain fell in just a few hours. Now, projections using the latest climate models show that this kind of extreme precipitation could grow more severe and frequent with climate change.

鈥淲hen the atmosphere gets warmer, there鈥檚 more water vapour in the atmosphere,鈥� says at the Scripps Institution of Oceanography in California. This well-known relationship means precipitation is generally expected to increase by around 7 per cent for each degree Celsius of warming.

But projecting the influence of climate change on precipitation at particular places is more complicated. Precipitation is affected by local differences in topography and changes in atmospheric circulation that aren鈥檛 captured by global climate models.

Pierce and his colleagues used a historical record of precipitation from 1950 to 2014 and the latest climate models to project changes in extreme precipitation in North America by the end of the century. They used a statistical method to link results from the climate model to the historical data to achieve higher resolution projections.

In addition to correcting for biases in the historical precipitation record that made extremes appear less intense, the researchers combined projections from many different models to capture more extreme events. Using the latest models also gave them a better view of atmospheric circulation, says Pierce.

Under a high-emissions scenario, they projected that the amount of precipitation in the most extreme events would increase by around 25 per cent on average across North America by the end of the century, excluding Arizona and New Mexico, where it increased by 15 per cent.

Extreme events would also become more frequent, according to their projections. In the US north-west and south-east, what would have been a once-in-a-century event would happen every 30 to 40 years by the end of the century under a high-emissions scenario. Once-in-500-years events would become more common across most of the continent.

鈥淭hat鈥檚 pretty shocking,鈥� says Pierce. 鈥淭hat鈥檚 a pretty big difference in how you manage the water.鈥�

While the results aren鈥檛 hugely different from those projected by older models, at the National Center for Atmospheric Research in Colorado says the state-of-the-science work makes him more confident in the projections. 鈥淚f you use different methods and they tell you the same story you have much more trust in the outcome,鈥� he says.

at the Breakthrough Institute, a California think tank, says putting numbers to changes to precipitation at such high resolution is especially valuable for flood management planning and for building infrastructure that can withstand the adverse impacts of climate change.

Prein says the results are consistent with an increase in extreme precipitation over North America seen in the past 10 or so years, from flooding in Houston, Texas, from Hurricane Harvey to California鈥檚 recent atmospheric rivers.

Connecting the downpour in Fort Lauderdale to climate change would require a formal attribution study, but Pierce says the rain, which shuttered the airport and flooded large parts of the city, is 鈥渆mblematic of the kind of thing you can see鈥�.