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Opinion | Climate change is melting Greenland and Antarctica’s ice. Time to act. – The Washington Post

As this month’s unseasonably high temperatures drove unprecedented melting of the Greenland ice sheet, experts delivered a chilling message: Get used to it. Massive stores of ice sit atop land in Greenland and Antarctica, and if even a small fraction melted into the oceans, sea levels would rise dramatically. Scientists are still figuring out how fast this might happen. But new research leaves little room for optimism.

Over the course of this century, countless millions of people will have to reckon with rising seas. There are few easy answers, but humanity must — with urgency — prepare now.

In a new paper in the journal Nature Climate Change, researchers estimated that Greenland’s “zombie ice” — immense chunks destined to melt because of the changes that have already occurred — will boost sea levels by nearly a foot. The scientists calculate that some 3.3 percent of the island’s ice sheet is bound to disappear into the oceans, much of that over the course of this century, which equates to 110 trillion tons of ice. These estimates, based on direct observations of Greenland, are more pessimistic than previous projections, which relied on computer modeling. According to the researchers, their new estimates represent the minimum that could happen if global warming were to continue.

These estimates do not take into account melting occurring in other areas, particularly Antarctica — and news from scientists on that end of the world, announced this month, was not good. A study published in Nature Geoscience revealed harrowing new details about Antarctica’s gigantic Thwaites Glacier — a frozen, Florida-size expanse also known as the “doomsday glacier” because its collapse could raise sea levels by 3 to 10 feet. Scientists are still figuring out how the glacier will respond to global warming. So researchers used an underwater robotic vehicle to map how the ice behaved when it encountered different sorts of circumstances in the past, particularly where it interacts with the seabed on which it is anchored. They found evidence that the ice responds quickly to adverse conditions, suggesting that “pulses of rapid retreat are likely to occur in the near future.” “Thwaites is really holding on today by its fingernails,” said the British Antarctic Survey’s Robert D. Larter, one of the co-authors.

What is rapid in geological time seems slow on human time scales. The most severe consequences of melting ice caps might not come for decades or even longer. Given how little the experts know about the dynamics of these behemoth ice formations, their predictions could still be off. But the world is already suffering the effects of a relatively modest rise in sea level. One example: New York City’s catastrophic flooding during Superstorm Sandy in 2012. Melting land-based ice is one of the most predictable repercussions of global warming. Accordingly, the earlier communities prepare, the more likely they are to minimize the damage of future disasters. Moreover, early preparation will cost less than responding too late.

Expensive engineering efforts will be justifiable for critical areas. Hampton Roads, for example, is home to expansive naval facilities and will require substantial investment in water-management projects. Manhattan, which Hurricane Sandy inundated, causing some $19 billion in damage, is even more vital to the U.S. economy. Construction has already begun on a $20 billion project to build raised parks, esplanades and barriers along Lower Manhattan. Local and federal officials are discussing other options, such as massive sea gates that would close off New York Harbor during big storms.

Even that grandiose plan might not make sense for Manhattan as it considers various ways to keep the water out. Proposals of this sort would be less justifiable for other places. A 2019 report from the Center for Climate Integrity found that the country could spend $400 billion building sea walls to protect coastal communities. As harsh as it sounds, there are certain places where it will not make sense to spend lots of money trying to keep back the tides. Some will have to be abandoned.

Smart planning is essential. State and local governments should impose building codes that account for ever-increasing flood risk, as Houston did after Hurricane Harvey flooded the city in 2017. Meanwhile, government at all levels should refuse to subsidize risky waterside development, such as by providing favorable flood insurance rates for flood-prone areas.

A recent reform to the Federal Emergency Management Agency’s National Flood Insurance Program brought premiums more in line with the risks homeowners face, substantially raising monthly costs for some property owners and eliciting howls of opposition. FEMA projects that far more coastal areas will face high flood risk by 2100, the high-risk zone expanding 55 percent, so it will be a perpetual challenge for property owners and the government to correctly gauge various places’ exposure.

Leaders must be tougher. At some point, localities will have to refuse to keep up roads, sewers and other services in areas people should not be living. States and localities such as New Jersey, following Hurricane Sandy, are buying up real estate in high-risk areas and converting it into floodplains and wetlands, natural flood barriers. Buyouts can be expensive for cash-strapped towns. But there are public-private models that show promise. Norfolk has explored ways to condition new construction in safer zones on developers helping to buy out properties in riskier areas. The federal government should also invest further in buyout efforts, enabling the National Flood Insurance Program to buy out homeowners rather than continually paying them to rebuild.

Yet, no matter how well-funded buyout programs are, some people will refuse to move, regardless of the risk. This will cause political problems, as people in battered communities demand government aid to rebuild in areas better abandoned. This will be true, too, in other zones that climate change renders more perilous, such as on the edges of forests increasingly liable to catch fire. The more the government shelters people from the true and increasing cost of the choices they make in the face of global warming, the bigger the eventual bill for society at large.

The world has been amply warned. Scientists have raised the alarm: sea-level rise is not a matter of “if” but a matter of “when and how much.” The nation’s leaders must not wait for the floodwaters to inundate their communities — or the wildfires to get worse, or the droughts to become more severe — to plan for the new reality.

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