Dec 13, 2017

Scientists Link Hurricane Harvey’s Record Rainfall to Climate Change

Houston, TX
USA
by
Henry Fountain
,
The New York Times
Evading a wave in Houston after Hurricane Harvey hit on Aug. 25. Photo: Brendan Smialowski, Agence France-Presse/Getty Images
Evading a wave in Houston after Hurricane Harvey hit on Aug. 25. Photo: Brendan Smialowski, Agence France-Presse/Getty Images

Climate change made the torrential rains that flooded Houston after Hurricane Harvey last summer much worse, scientists reported Wednesday.

Two research groups found that the record rainfall as Harvey stalled over Texas in late August, which totaled more than 50 inches in some areas, was as much as 38 percent higher than would be expected in a world that was not warming.

While many scientists had said at the time that Harvey was probably affected by climate change, because warmer air holds more moisture, the size of the increase surprised some.

“The amount of precipitation increase is worse than I expected,” said Michael J. Wehner, a senior scientist at Lawrence Berkeley National Laboratory and an author of a paper on his group’s findings, which included the 38 percent figure. Based on how much the world has warmed, Dr. Wehner said, before the analysis he had expected an increase of only about 6 or 7 percent.

The other study, by an international coalition of scientists known as World Weather Attribution, found that Harvey’s rainfall was 15 percent higher than would be expected without climate change. Geert Jan van Oldenborgh of the Royal Netherlands Meteorological Institute and the lead author of the second study, said that climate change also made such an extreme rainstorm much more likely.

“The probability of such an event has increased by roughly a factor of three,” he said. While the likelihood of a Harvey-like storm was perhaps once in every 3,000 years in the past, he said, now it’s once every 1,000 years or so — which means that in any given year, there is 0.1 percent chance of a similar storm occurring along the Gulf Coast.