At least 10 feet of sea level rise is now guaranteed worldwide; it's all but inevitable, a done deal. An ice sheet two miles thick has collapsed in West Antarctica—glaciologists have been dreading this moment for decades, though in recent years, it was more of a question of when than if—and there is nothing that can stop it from melting now.
NASA scientists say so, glaciologists say so, researchers who've spent their entire careers studying the slow and increasingly inevitable melt of our planet's permanent ice stores say so. They say so in two new studies debuting this week; one in Science and one in Geophysical Research Letters. They are all saying we should begin getting comfortable with sea levels that lap up 10 feet higher on our shores.
Long before the collapse of West Antarctica's Thwaites ice sheet, an organization called Climate Central created this interactive map, which shows how various levels of sea level rise will impact the United States. Grimly and fortuitously, it goes up to 10 feet—the amount that is now locked-in, but by no means the minimum of sea level rise we can expect to experience thanks to climate change. Go ahead, plug your city in, and see what percent chance you have of being driven away by high waters.
For instance, 99.5 percent of the population of New Orleans, Louisiana, as if they haven't suffered enough, will again find themselves underwater when the seas rise 10 feet. Thirty percent of all of the homes in Florida will be submerged; that's 5.6 million people. Fort Lauderdale, for one, will be nearly below the waves. Only 9 percent of New York City will have to relocate in the face of rising tides, but then, that means 700,000 people will have to find new homes—twice as many as New Orleans.
Even if you don't live at or near sea level in one of those vulnerable areas, the crisis the rise will bring will impact you too; it will either cost heady sums to shore up the flood-walls and prepare the dikes, or chaos and misfortune will reign when a disaster—a hurricane, for instance—hits. Either way, rising seas are a hugely destabilizing force.
That degree of sea level rise may take decades yet—the Science study says it will take 200 years to melt the entire sheet, but other studies say the melt could be more rapid. It is driven by warmer waters, not warmer air; in West Antarctica, these great ice sheets are slowly warmed from below, then beaten apart by more ferocious winds—another feature of a climate-changed world, scientists surmise. And the risk is so much greater than 10 feet; the Greenland ice sheet and the other Antarctic stores hold 200 feet of sea level rise in their softening doomsday banks.
Whether we melt all or much of that remaining permanent ice depends on whether we decide to slow our rate of carbon emissions, civilization-wide. If we do not, it will be far more than coastal cities in Florida that we need worry about. If we are smart, we will act swiftly to mitigate our industrial pollution, and begin planning for higher tides. So far, we have not been smart.
"This is really happening," said Thomas P. Wagner, who runs NASA's programs on polar ice, told the New York Times. "There's nothing to stop it now."
[Update; I have deleted a clause that stated with undue certainty that the melt could unfold in decades—while technically accurate, it does not reflect the finding of the studies discussed here. I have also specified that New Orleans will be 99.5 percent underwater, not the entire state of Louisiana.]