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, thanks to man-made climate change, a study said.
And looking ahead, the chances will likely triple once again by 2100.
In the 1980s and 1990s, there was a 1% chance of a 20-inch rainfall somewhere in Texas. Now it's up to 6% and by the end of the century, it'll be up to 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 peer-reviewed 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 likely 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?" he 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."
To conduct the study, Emanuel used computer models to simulate past, present and future storms in Texas, plugging in what scientists project the planet's atmosphere will be like later this century.
"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," Emanuel says. "People have to understand that damage is usually caused by extreme events."
While several scientists praised the study, Christopher Landsea, science operations chief at the National Hurricane Center, shared some doubts. He said Emanuel’s results don’t fit with other climate change model projections that show higher rainfall totals but also show a decrease in the number of tropical storms and hurricanes.
Contributing: The Associated Press