The trouble with Thwaites, which is one of the largest glaciers on the planet, is that it’s also what scientists call “a threshold system.” That means instead of melting slowly like an ice cube on a summer day, it is more like a house of cards: It’s stable until it is pushed too far, then it collapses. When a chunk of ice the size of Pennsylvania falls apart, that’s a big problem. It won’t happen overnight, but if we don’t slow the warming of the planet, it could happen within decades. And its loss will destabilize the rest of the West Antarctic ice, and that will go too. Seas will rise about 10 feet in many parts of the world; in New York and Boston, because of the way gravity pushes water around the planet, the waters will rise even higher, as much as 13 feet. “West Antarctica could do to the coastlines of the world what Hurricane Sandy did in a few hours to New York City,” explains Richard Alley, a geologist at Penn State University and arguably the most respected ice scientist in the world. “Except when the water comes in, it doesn’t go away in a few hours – it stays.”
With 10 to 13 feet of sea-level rise, most of South Florida is an underwater theme park, including Miami, Fort Lauderdale, Tampa and Mar-a-Lago, President Trump’s winter White House in West Palm Beach. In downtown Boston, about the only thing that’s not underwater are those nice old houses up on Beacon Hill. In the Bay Area, everything below Highway 101 is gone, including the Googleplex; the Oakland and San Francisco airports are submerged, as is much of downtown below Montgomery Street and the Marina District. Even places that don’t seem like they would be in trouble, such as Sacramento, smack in the middle of California, will be partially flooded by the Pacific Ocean swelling up into the Sacramento River. Galveston, Texas; Norfolk, Virginia; and New Orleans will be lost. In Washington, D.C., the shoreline will be just a few hundred yards from the White House.