Hurricanes and Cyclones

(Bloomberg) -- Focus the sun’s beams on the tropical ocean at peak intensity. Add in warm, moist air. Stir the pot with the motion of the spinning globe. The results become the most powerful storms on Earth, whether they’re called hurricanes, typhoons, cyclonic storms or tropical cyclones. Climate change is making warm water, the fuel for storms, more abundant, and rising sea levels are making storm surge more destructive. Rapid development means that 3 billion people — roughly 40 percent of the world’s population — now live within 200 kilometers (124 miles) of a coastline; it’s projected that by 2050 more than 1 billion will live directly at the water’s edge. While the world’s governments wrangle over sweeping measures to limit global climate change, coastal communities face hard and very specific choices about where to fight to keep storm surges at bay, and where to let Mother Nature have her way.

The Situation

Massive flooding and a high death toll from Cyclone Idai, which first made landfall in southeast Africa March 15, focused the world’s attention once more on such storms. More and more researchers are linking climate change to the severity of specific weather events. One study concluded that as much as 38 percent of the rainfall from Hurricane Harvey, which caused catastrophic flooding in Houston in 2017, was likely the result of global warming. A year later, voters in and around Houston elected by more than 4 to 1 to approve $2.5 billion in bonds for projects aimed at preventing a repeat of the flooding. Also in 2018, the U.S. Army Corps of Engineers held public hearings on a series of options to protect the New York City region from a repeat of the damage caused by what’s become known as superstorm Sandy in 2012. One proposal calls for harbor-wide storm-surge barriers to hold back the ocean, a project that could cost $30 billion. Similar barriers are already in place protecting London and coastal areas of the Netherlands.

The Background

Cities have long responded to disasters by building up. After being hit by the deadliest hurricane in U.S. history in 1900, Galveston, Texas, built a 10-mile sea wall and raised its city blocks by as much as 17 feet. New Orleans has used levees and canals to harness the Mississippi River for 200 years, though critics say they have destroyed wetlands that used to protect southern Louisiana from storm surges. And flawed levee design led to flooding from Hurricane Katrina in 2005; about 1,200 people died overall and three-quarters of homes in the New Orleans area were damaged. Cyclone Bhola killed more than 300,000 people in Bangladesh in 1970, so the nation constructed coastal embankments along with modernizing its early-warning systems and developing shelters and evacuation plans. But as sea levels rise, storms don’t have to hit cities directly to cause damage: In 2017, Hurricane Irma made landfall on Florida’s west coast but pushed the Atlantic 4 to 6 feet above ground level in Miami-Dade County, on the state’s eastern side. Asia’s urban river deltas have become particularly vulnerable to surge since its cities transformed themselves into major metropolitan areas. Central Shanghai is now 2 meters below mean sea level and relies on embankments for protection. By 2050, the city could face another 13 to 25 centimeters of sea-level rise. A study released in April 2018 suggested that all but six of Tokyo’s 23 wards would flood in the surge from a super typhoon.  

The Argument

Should countries respond to the rising threat from hurricanes by fortifying coastal communities or by abandoning them? Environmentalists often oppose sea barriers, arguing that they choke off tidal flows that support marine life and merely push flooding elsewhere. And there isn’t enough money to build them everywhere. But retreat has proved less popular: After Sandy, the federal government gave New Jersey $300 million to buy homes vulnerable to storm flooding, but in the program’s first four years, opposition from local governments meant that only half the money was spent. Louisiana is developing the most aggressive response to climate-linked flooding in the country: It envisions the eventual movement of thousands of people from areas threatened by the rising Gulf of Mexico. So far, the idea hasn’t gone over well with those the plan would relocate. In New York, the alternative to the giant sea barrier would be block-by-block decisions on what parts of low-lying areas to protect and which to hand over to the sea. In the U.S., flood insurance is federally subsidized, and the program has been blamed for encouraging overdevelopment of vulnerable areas. In China, researchers have suggested that threatened areas should enhance natural flood defenses, that is, do more to preserve reefs and mangrove swamps, and consider constructing artificial reefs.

The Reference Shelf 

• A related QuickTake on the debate over how hurricanes are measured.
• A Nature Geoscience article reviewing studies on the effect of climate change on tropical cyclones.
• The World Meteorological Organization’s Tropical Cyclone Program page.
• The U.S. National Hurricane Center site has pages on the tropical weather outlook, recent satellite imagery, storm surge and the Saffir-Simpson hurricane scale.
• The U.S. National Oceanic and Atmospheric Administration has a collection of hurricane tracks since 1842.
• The Engineering for Climate Extremes Partnership promotes resilience in the face of climate change. 
• Residents of Isle de Jean Charles talk to Bloomberg in “The First U.S. Climate Refugees.” 

To contact the editor responsible for this QuickTake: John O'Neil at joneil18@bloomberg.net

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