"You’re rolling the dice every year," said Kerry Emanuel of the Massachusetts Institute of Technology (MIT), US, who came up with the result. "And we believe the odds of a flood like Harvey are changing."

Emanuel’s findings could help city planners and government officials decide how to fortify infrastructure as well as whether to upgrade building standards to deal with stronger storms and more damaging floods.

Whilst global climate models have a resolution too coarse to simulate hurricanes well, Emanuel has created hurricane-simulating models with a fine resolution that he can embed inside global climate models. Using this technique, he was able to calculate the probability of at least 500 mm of rain occurring near Houston or in Texas as a whole.

"When you take a very, very rare, extreme rainfall event like Hurricane Harvey, and you shift the distribution of rain toward heavier amounts because of climate change, you get really big changes in the probability of those rare events," said Emanuel. "People have to understand that damage is usually caused by extreme events."

Emanuel reported his findings in PNAS.