ON AUGUST 29th 2005, Hurricane Katrina made landfall in southern Louisiana. As it travelled north, it overwhelmed the levee system designed to protect New Orleans. By August 30th, 80% of the city was underwater. More than 1,800 people died in what became the costliest natural disaster in American history. The Army Corps of Engineers, which designed the old network of floodwalls, called it “a system in name only”.
Precisely 16 years later, another fearsome storm, Hurricane Ida, gathered strength in the Gulf of Mexico’s warm waters. The quickly-formed storm cohered south of Cuba and had hardly acquired a name before she was threatening Louisiana’s coastline. A huge patch of unusually warm water provided fuel for Ida to intensify into a category-four storm (the Saffir-Simpson hurricane wind scale goes from one to five, with anything above three considered “major”; after making landfall Ida was downgraded to a tropical storm). Many feared that history was about to repeat itself. The preliminary good news is that it did not: the improved levee system built after Katrina to protect New Orleans and its environs, just nearing completion, appears to have held. But there was plenty of bad news, too.
Louisiana has more covid cases per 100,000 people than almost any other state. Its hospitals are jammed almost to capacity, making it all but impossible to move patients from the southern part of the state to other facilities farther inland. Consequently, hospitals directly in Ida’s path were not evacuated, though dozens of nursing homes were. At the time of writing, the consequences of those grim choices—moving older, vulnerable people around, and leaving the hospitalised in place—remain unclear. But the New Orleans Times-Picayune reported that hours into the storm, in Thibodaux, near to where Ida made landfall, one hospital’s intensive-care unit lost generator power, forcing doctors to manually ventilate patients as they were moved around within the building.
The hospital was not alone: the hardest hit parts of the city of New Orleans could be without power for weeks. In Kenner, a large suburb, officials told residents that they could be without water for five days and power for three weeks. The city’s sewer board warned, meanwhile, that the outage could affect a “very significant” number of its 84 pumping stations.
The worst impact may be felt by those outside of the levee system. New Orleans is flanked by vulnerable coastal communities already in danger of being wiped off the map by rising sea levels, and Ida looks to be hastening that job. The most endangered areas include Grand Isle, a popular barrier island two hours south of New Orleans, and Isle de Jean Charles, an eroding islet in Terrebonne Parish that has long been occupied by Native Americans. LaPlace, west of New Orleans along the Mississippi river, was swamped by floodwaters; rescue crews tried through the night to reach stranded residents. The most severely hit place may be Port Fourchon, near Grand Isle, where most ships that supply the Gulf of Mexico’s productive oil platforms and rigs dock.
Storms have long battered Louisiana, but climate change is likely to be making things worse. That is not because storms are growing more frequent. Whether climate change increases the frequency, as opposed to the intensity, of storms is less clear. At least one database of hurricanes that have affected America since 1900 shows no long-term increase in the frequency of storms that have made landfall. Some models suggest that the number of hurricanes in the north Atlantic could even decrease between now and the end of the century. That is less reassuring than it sounds.
Hurricanes draw their energy from heat in the oceans beneath them. Most of the heat gained by the planet as a result of climate change is stored in the oceans; it stands to reason that tropical cyclones (which are called hurricanes in the Atlantic ocean and typhoons in the Pacific) should become more intense as the climate warms. Data bear this out: the latest review carried out by the Intergovernmental Panel on Climate Change deemed it “likely” that the share of storms classed between categories three and five has increased over the past 40 years. This trend is projected to increase as the planet warms.
That may prove particularly difficult for southern Louisiana. The earthen levees that protect New Orleans deprive the surrounding wetlands of necessary sediment. And man-made canals from a century of oil and gas exploration have made what remains of the coast even more vulnerable. Ida may not have been as destructive as Katrina was 16 years ago, but it is nonetheless a harbinger of a grim future.