According to the Intergovernmental Panel on Climate Change, sea levels could rise by more than three feet by the end of this century. The United States Army Corps of Engineers projects that they could rise by as much as five feet; the National Oceanic and Atmospheric Administration predicts up to six and a half feet. According to Wanless, all these projections are probably low. In his office, Wanless keeps a jar of meltwater he collected from the Greenland ice sheet. He likes to point out that there is plenty more where that came from.

“Many geologists, we’re looking at the possibility of a ten-to-thirty-foot range by the end of the century,” he told me.

We got back into the car. Driving with one hand, Wanless shot pictures out the window with the other. “Look at that,” he said. “Oh, my gosh!” We’d come to a neighborhood of multimillion-dollar homes where the water was creeping under the security gates and up the driveways. Porsches and Mercedeses sat flooded up to their chassis.

“This is today, you know,” Wanless said. “This isn’t with two feet of sea-level rise.” He wanted to get better photos, and pulled over onto another side street. He handed me the camera so that I could take a picture of him standing in the middle of the submerged road. Wanless stretched out his arms, like a magician who’d just conjured a rabbit. Some workmen came bouncing along in the back of a pickup. Every few feet, they stuck a depth gauge into the water. A truck from the Miami Beach Public Works Department pulled up. The driver asked if we had called City Hall. Apparently, one of the residents of the street had mistaken the high tide for a water-main break. As we were chatting with him, an elderly woman leaning on a walker rounded the corner. She looked at the lake the street had become and wailed, “What am I supposed to do?” The men in the pickup truck agreed to take her home. They folded up her walker and hoisted her into the cab.

To cope with its recurrent flooding, Miami Beach has already spent something like a hundred million dollars. It is planning on spending several hundred million more. Such efforts are, in Wanless’s view, so much money down the drain. Sooner or later—and probably sooner—the city will have too much water to deal with. Even before that happens, Wanless believes, insurers will stop selling policies on the luxury condos that line Biscayne Bay. Banks will stop writing mortgages.

[...]

As the ice age ended and the planet warmed, the world’s coastlines assumed their present configuration. There’s a good deal of evidence — much of it now submerged — that this process did not take place slowly and steadily but, rather, in fits and starts. Beginning around 12,500 B.C., during an event known as meltwater pulse 1A, sea levels rose by roughly fifty feet in three or four centuries, a rate of more than a foot per decade. Meltwater pulse 1A, along with pulses 1B, 1C, and 1D, was, most probably, the result of ice-sheet collapse. One after another, the enormous glaciers disintegrated and dumped their contents into the oceans. It’s been speculated — though the evidence is sketchy — that a sudden flooding of the Black Sea toward the end of meltwater pulse 1C, around seventy-five hundred years ago, inspired the deluge story in Genesis.