Double Trouble

One Hurricane Katrina or Hurricane Harvey is a disaster. But having two such hurricanes hit the same area within a few weeks of each other is catastrophic. Coastal infrastructure is demolished, hundreds of thousands are left homeless, and it takes years for the region to recover.

Until recently, the odds of back-to-back storms have been small. But a recent study says that our changing climate appears to be boosting those chances. Some regions of the Atlantic and Gulf coasts of the U.S. could see double hits as often as every three years.

Researchers used computer models to simulate what could happen under modest or major increases in global temperatures by the end of the century. Higher temperatures may not make more tropical storms. But studies say they are likely to make the storms more intense, with higher storm surges, stronger winds, and much heavier rainfall.

At the same time, higher temperatures will increase global sea levels. That will make it harder to maintain coastal infrastructure—sea walls, drainage systems, water and power supplies, and more. A single powerful storm could swamp those systems, while a double hit could knock them out for months or longer.

The researchers recommended that both local and national officials begin preparing for such events—upgrading infrastructure and expanding emergency response capabilities, for example. That could make it easier to bounce back from stormy doubleheaders.