Losing Louisiana

Seventy miles south of New Orleans, on the eastern end of Grand Isle, a small tide gauge records the Gulf of Mexico rising against the surrounding land. The monthly increases are microscopic, narrower than a single strand of hair.

Climate scientists recording those results think they add up to something huge. The gauge, they say, may be quietly writing one of the first big stories in the age of global warming: the obituary for much of southeast Louisiana.

In 50 to 100 years, the numbers tell them, rising seas caused by global warming, combined with the steady subsidence of Louisiana's coast, will lift the Gulf of Mexico two to six feet higher in many areas surrounding New Orleans.

Such a rise would overwhelm the most ambitious coastal restoration plans now under way and submerge almost everything in southeast Louisiana outside hurricane levees. And that means the areas inside the levees essentially would become coastline, far more vulnerable to hurricanes and continuing coastal erosion, and in need of a far more drastic and expensive flood protection apparatus.

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