New Orleans is the size of Sheffield. The comparison gives some context to the extraordinary order for the Big Easy to be abandoned to the flood- waters of Hurricane Katrina that have turned its elegant and vibrant streets into reeking canals. Efforts to evacuate the tens of thousands who remain are increasingly urgent. The task is taxing the full might of the US federal emergency services, who have been slow to respond to the emerging crisis, a crisis that has particularly hit the region ’s poor. Before long, the citizens who remain may well be outnumbered by the alligators and snakes that have made their way downtown from the city’s surrounding bayous. They lend the carnage a primeval quality.

Katrina has indeed created cata- strophe on a rare scale. Much of southern Louisiana and Mississippi has been swamped. The hurricane, which in an hour generated the same amount of power that the US uses in a year, has left seven million people without electricity. Those still trapped in New Orleans are relying on heli-copter drops for food and water. Babies have been airlifted to other states without their mothers. Only twice in the 20th century did nature wreak comparative damage on the US. In

1900 a hurricane killed up to 12,000 in the Texas Gulf port of Galveston. Up to 6,000 died in the 1906 San Francisco earthquake and following fires. The Mayor of New Orleans has suggested that Katrina’s death count will run to thousands in his city alone. His estimate was based on little evidence. Tragically, it may yet prove sound.

It is alarming that the authorities of this superpower are struggling to bring swift relief. The job would have been easier if the 100,000 citizens who decided to ride out Katrina had obeyed the mandatory evacuation order, but their vulnerability highlights our broader human fragility.

Widespread looting has also diverted the National Guard. But there have been shortcomings. Communications between different agencies, for instance, are poor or non-existent. The response also lacks an effective figurehead in the way that Jeb Bush, the Governor of Florida, used his hotline to the White House to rally relief efforts when his state was hit by four hurricanes and tropical storms last year.

Katrina’s origins, and whether she was a progeny of global warming, is an inevitable but not necessarily useful debate. Hurricanes follow a 50-year cycle. In the 1950s, thirty-seven tropical storms hit the US, of which ten were major hurricanes. In the 1990s, when fears of climate change began to bite, the US had just nineteen such storms, of which only five were major hurricanes. It is possible, therefore, that we are seeing nature repeat itself. However, Atlantic sea temperatures are at record highs compared with the past 50 years when such measurements have been taken. These rises could have given Katrina extra punch, but so may have its erratic path through the warmer waters of the Gulf of Mexico.

Katrina is a disaster on many levels. But it would be wrong to suggest that New Orleans will never recover. The will and wealth of the nation that picked itself up after 9/11, and which decided to rebuild San Francisco on the San Andreas fault, is not in question. In one way life will not be the same. The World Meteorological Organisation retires the names of hurricanes that have been particularly destructive from its rotating six-year list. There will never be another Katrina.