Filed Under:Risk Management, Weather Risk

Science confirms Hurricane Harvey was indeed 'biblical'

New analysis may be the first to deploy an approach that comprehensively analyzes the changing probability of a storm hitting over time.

Matt Looingvill struggles with his umbrella as he tries to walk in the wind and rain, Friday, Aug. 25, 2017, in Corpus Christi, Texas. (AP Photo/Eric Gay)
Matt Looingvill struggles with his umbrella as he tries to walk in the wind and rain, Friday, Aug. 25, 2017, in Corpus Christi, Texas. (AP Photo/Eric Gay)

(Bloomberg) -- When Hurricane Harvey dropped 60 inches of rain on Houston in August, some described the storm as “biblical.” One of America’s leading hurricane scientists has now sharpened that assessment. 

Houston rainfall


“By the standards of the average climate during 1981-2000,” MIT’s Kerry Emanuel writes in Proceedings of the National Academy of Sciences, “Harvey’s rainfall in Houston was ‘biblical’ in the sense that it likely occurred around once since the Old Testament was written.”

Related: Tallying Harvey's tragic price, one storm-ravaged home at a time

Emanuel’s analysis attempts to answer a series of questions critical to recovery and rebuilding in Houston and elsewhere: “Should buildings, homes, roads, and associated infrastructure be built in the same place again?” he wrote. Are building codes, levees and sea walls tough enough for the future? As the world warms, every community will have to grapple with these questions on their own.

Hotter seas, more humid air


Climate scientists continue to project that as the century goes on, hotter seas and more humid air are likely to make tropical storms more intense. The first volume of the latest U.S. National Climate Assessment, released by the Trump administration earlier this month, reports scientists having higher confidence in their finding that storms will carry more precipitation.

Global warming has already helped increase the annual likelihood of Harvey-like rainfall sixfold since the end of the 20th century, to about 6%, Emanuel writes. Before this century’s out, that probability may rise to 18%. 

Researchers such as Emanuel are working with hurricane records that are historically short and incomplete. The best data have come since 1980, and while scientists have greater confidence in their projections going forward, the historical record is still very noisy.

Powerful computer models


Information can be gleaned by combining observations with well-understood meteorological physics and with powerful computer models that can simulate past trends and “run” thousands of future storms. 

“It’s a ground-breaking paper,” said Adam Sobel, an earth and environmental sciences professor at Columbia University. He said that Emanuel’s work may be the first to deploy an approach that comprehensively analyzes the changing probability of a storm hitting over time.

Related: Determining business interruption losses after Hurricane Harvey

The report’s conclusion is “stunning” and consistent with Houston’s recent spate of floods, but raises more questions than it answers, Sobel said. For instance, Emanuel was unable to determine why Hurricane Harvey stalled over Houston.

There are no facts about the future, the saying goes. Until there are, physics models tuned with historical data are the next best thing. 

Related: How insurers and reinsurers track live hurricanes in real-time

Copyright 2017 Bloomberg. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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