‘Biblical’ deluges are getting a lot more likely

Houston, you have a problem. The odds of a storm dumping Harvey-like rain on Texas have gone up sixfold in the past 25 years because of man-made climate change, a study says. And looking ahead, the chances probably will triple that by 2100.

In the 1980s and 1990s, there was a 1% chance of a 20-inch rainfall somewhere in Texas in a given year. Now it’s up to 6%, and by the end of the century, it’ll hit 18%, said meteorologist Kerry Emanuel of the Massachusetts Institute of Technology, who led the study.

“That’s a huge increase in the probability of that event,” and the change is the result of global warming, he said. The study appeared in the peerreviewed Proceedings of the National Academy of Sciences.

Harvey dumped a U.S. storm record of 5 feet of rain across southeastern Texas in late August, leading to catastrophic flooding and the nation’s worst natural disaster since Katrina in 2005. Harvey killed at least 70 people and caused at least $100 billion in damage.

“Harvey’s rainfall in Houston was ‘biblical’ in the sense that it likely occurred around once since the Old Testament was written,” the study said.

Emanuel said he hurried the study to help Houston officials think about what conditions they should consider when they rebuild.

“Should you be putting in a more advanced storm-sewer system that may cost billions of dollars, or not?” Emanuel said. “The answer to that question depends upon whether you think Harvey was a one-off — very unlikely to happen any time in the next 100 years — or whether it may be more common than you thought.”