Can geoengineering plans save glaciers and slow sea level rise?

Only four ships have ever visited the place where Thwaites Glacier pours off the coast of West Antarctica. This swath of ocean resembles a rugged, white desert — a plain of wind-sculpted ice dotted with sheer-sided mesas that tower seven to 10 stories above the surrounding terrain.

Those mesas are icebergs larger than aircraft carriers. They break from the glacier itself and from the rest of the West Antarctic Ice Sheet, a dome of ice as large as Mexico slowly oozing seaward like a heap of frozen custard.

As the winds and ocean currents push the icebergs around, they plow through the meter-thick sea ice that covers the water, as if it were the fragile skin that forms on a cooling bowl of tomato soup.

In the coming century, a pivotal drama between humans and nature could play out here. In a quest to slow down sea level rise, a few researchers are sketching out massive engineering and construction projects that could block ocean currents, alter the flow of some of the world’s largest glaciers and potentially delay or prevent a major collapse.

Even compared to the Great Wall of China, some of the proposed projects would be “just enormous,” says Christian Rodehacke, a glaciologist at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany. With structures potentially as tall as the Empire State Building, such a project could be the largest effort ever undertaken by humans to modify Earth.

The West Antarctic Ice Sheet is stabilized by undersea mountains that rise to form a jagged dike beneath its outer edges, but low spots in the dike provide gaps where gigantic corridors of fast-moving ice slide into the ocean. Thwaites, reaching more than 400 kilometers upstream into the heart of West Antarctica, is the most vulnerable of these glaciers, and the widest glacier in the world. Its coastal outlet is 130 kilometers across and dips as far as 1.2 kilometers below sea level — exposing it to warm, dense, salty ocean currents that flow like rivers along the seafloor.

Thwaites holds 480,000 cubic kilometers of ice. It’s losing about 80 cubic kilometers per year — a sixfold increase since the 1990s — and its rate of loss is expected to increase more. As the glacier thins, it lifts off the seafloor, gradually losing its connection with the dike below. Because of this, the speed of the glacier’s western branch has accelerated by more than 70 percent since 1973, reaching 4 kilometers per year. It is losing volume ever more quickly as it melts and sheds icebergs.

The events unfolding here present humankind with a range of possible futures: At the optimistic end, the glacier keeps its death grip on the protective dike long enough for us to dramatically curb greenhouse gas emissions and remove planet-warming carbon dioxide from the atmosphere. In this case, Antarctica contributes only about 10 centimeters of sea level rise by 2100 and roughly a meter by 2300, with the rate of rise gradually tapering off over the next few centuries.

At the other extreme, Thwaites thins enough to lose its grip, further accelerating and fragmenting into icebergs. This could unleash an irreversible collapse across the West Antarctic Ice Sheet, with the continent contributing 20 to 50 centimeters of sea level rise by 2100, and up to four to seven meters by 2300, drowning population centers in California, Florida, Louisiana, South Carolina, the Netherlands, Pakistan, Bangladesh, Vietnam, Thailand, the Philippines and many other places.

In all of these scenarios, many more centimeters of sea level rise will come from other sources, like thermal expansion of oceans and melting Arctic glaciers, further worsening the situation.

There is no consensus on when Thwaites will start to collapse or what temperatures will trigger it. Some scientists believe that Thwaites has already entered the early stages of its demise. Others think it will cross that invisible threshold in the coming decades. This is prompting some researchers to step beyond the role of simply documenting the demise of glaciers — and make audacious plans to intervene, to save a handful of crucial glaciers that could set off runaway sea level rise.

Normally staid and cautious scientists are now willing to speak aloud the things that they’ve been quietly thinking for years. A prominent science-fiction novelist has launched the idea into public consciousness. And tech entrepreneurs have volunteered to find ways to fund the research, which government agencies consider too controversial to touch.

The proposed ideas would be expensive, logistically challenging and legally fraught. The mere idea of engineering glaciers has provoked heated disagreement among well- respected scientists who have worked together for decades, reflecting deep philosophical and political divides over how society should respond to climate change.

Not talking about this because it makes people uncomfortable feels like “a dereliction of duty” for scientists who are taxpayer-funded, says Slawek Tulaczyk, a glaciologist at the University of California, Santa Cruz who has long thought about engineering glaciers. “Maybe the conclusion will be that we should not do it,” he says, but to shut it down before real research has happened feels “politically motivated.”

Erin Pettit, a glaciologist at Oregon State University in Corvallis, sees it differently. Pettit, who has studied West Antarctica for two decades and has collaborated with Tulaczyk, says glacial engineering is a Band-Aid that could divert money and attention from addressing the underlying problems of climate change. If people are working to stop sea level rise from Antarctica, she fears, “we’re not going to care as much about solving the problem” by stopping carbon emissions. She also fears that engineering glaciers or ocean currents could alter the environment in unexpected ways.

Even proponents admit that glacial engineering will address only one symptom of climate change — sea level rise — while leaving problems such as heat waves, permafrost thaw, intensified hurricanes and ocean acidification unchecked. What’s more, unlike in Antarctica, glaciers in Greenland and the Arctic are experiencing massive surface melting, making them a bit less likely to respond to the same interventions.

Yet glacial engineering might become necessary. Even optimistic scenarios for global warming, in which CO₂ levels peak and level off by 2070, might still lead to Thwaites’ collapse. “Every ice dynamicist on the planet ought to be looking at this,” says John Moore, a glaciologist at the University of Lapland in Finland.

A stuck glacier inspires glacial geoengineering ideas

People have talked for decades about engineering ice to serve human purposes in one grand way or another. During World War II, the Allied countries considered building artificial icebergs reinforced with sawdust to create aircraft carriers impervious to German torpedoes. In the 1960s, Soviet scientists proposed building an 80-kilometer barrier across the Bering Strait, from Alaska to Russia, to change ocean currents, reduce sea ice and open vast swaths of Arctic permafrost for farming. During the 1970s, a pair of physicists suggested that nuclear waste could be stored deep in ice sheets. And in the ’70s and ’80s, engineers in Saudi Arabia suggested that icebergs towed from Antarctica could provide freshwater to places lacking it.

Douglas MacAyeal was a graduate student at Princeton in 1983 when he read about those proposals to use icebergs as a source of freshwater. Inspired, he submitted a brief abstract to a scientific meeting suggesting a way to prevent glacial flow from speeding up in the face of a warming climate: Large amounts of seawater pumped onto the floating fronts of glaciers would freeze there, thickening the ice and causing it to rest more heavily on submarine mountains beneath. Anchoring the floating ice to submerged mountains would help it buttress and slow the glacier flowing from behind.

MacAyeal never pursued the idea. “That was a time of life for me when I have to write papers that are taken seriously, so I can get a job,” he says. This “silly idea” wouldn’t get him there. He eventually landed at the University of Chicago, rejoining the conversation on glacial engineering only in 2023, as he was retiring.

For Tulaczyk, the roots of his own idea for glacial engineering began in the 1990s while working on his Ph.D. He was studying the Siple Coast of West Antarctica, roughly 1,200 kilometers east of Thwaites, where six massive glaciers called ice streams ooze off the coastline.

These glaciers generally slide 300 to 700 meters forward per year. But scientists found that one, the Kamb Ice Stream, flows only about one-fiftieth that speed. Though Kamb used to move as quickly as its neighbors, it ground to a near-halt around 150 years ago.

Some scientists, such as Tulaczyk, attributed this slowdown in part to the loss of lubrication that normally allows glaciers to slide easily over their rough, gravelly beds. Most glaciers have a thin layer of liquid water beneath them. It’s produced as the bottom of the ice slowly melts, a few penny thicknesses per year, from both the heat of friction and the heat trickling out of the earth. The water beneath Kamb seemed to have migrated beneath a different glacier, like a river jumping its banks, causing Kamb to stagnate.

By the late 2000s, Tulaczyk had started wondering if it might be possible to slow down other glaciers intentionally, by mimicking what might have happened at Kamb. He imagined drilling a narrow hole through a glacier and pumping out the water beneath. The glacier might eventually freeze to its bed, as Kamb had, remaining stalled for decades or centuries.

Tulaczyk presented his idea to a small gathering of climate scientists in 2008. But when he asked the U.S. National Science Foundation to fund a workshop so scientists could further discuss it, he was sharply rejected. Tulaczyk suspects the agency was uncomfortable supporting such a seemingly radical idea because it might provoke negative reactions from a public that ordinarily supports climate research, or draw unwelcome attention from Congress, which approves funding for the agency.

Could we freeze glaciers to the seabed to slow sea level rise?

A pair of coincidences helped revive the idea a decade later.

Around 2018, Tulaczyk received an email from the sci-fi novelist Kim Stanley Robinson, who happened to be one of the few nonscientists in the audience when Tulaczyk gave his talk in 2008. Robinson chatted with him about the idea, and later included it in his 2020 novel, The Ministry for the Future, in which humans successfully respond to climate change and sea level rise. In the book, a glaciologist — named Slawek with Tulaczyk’s OK — concocts the same strategy for slowing and stabilizing glaciers.

Later, in 2023, Tulaczyk received an email from Alex Luebke, who had spent years founding tech companies, developing satellites and running advanced projects at Google X. Luebke had read Robinson’s book, loved the idea of engineering glaciers and wanted to talk with Tulaczyk about how to advance it.

Luebke, glaciologist Kenneth Mankoff, a former graduate student of Tulaczyk’s, and several other people convened a workshop at Stanford University in December 2023 aimed at mapping out how to test the feasibility of glacial engineering and how to find private funding.

The very idea provoked strong reactions among the people invited. “My first reaction was, ‘This is crazy’, ” admits Martin Truffer, a glaciologist at the University of Alaska Fairbanks who has known Tulaczyk for 30 years. “I was really hesitant whether I should go or not.”

But Mankoff, of NASA’s Goddard Institute for Space Studies in New York City, persuaded Truffer and many others. Fifty scientists from around the world showed up. When the group was asked on the first morning who was against glacial engineering, roughly half the hands went up. When asked who was undecided, the other half went up, including Tulaczyk’s. And when the moderator asked who currently supported the idea, a couple of hands might have wavered, but none went up.

To Tulaczyk, it was a good start. “Nobody is saying that we are ready to do anything at scale,” he says. This current effort “is about calling for this type of research to become a legitimate research area.”

Mankoff, Truffer and Tulaczyk are now making plans to test Tulaczyk’s idea along with Christine Dow, a subglacial hydrologist at the University of Waterloo in Canada, and Jenny Suckale, a geophysicist at Stanford. The team, which is looking for funding from private foundations, might conduct its first small experiments as soon as next summer, at a small glacier in Alaska. The researchers will use a jet of hot water to melt a bowling ball–sized hole through the ice and then pump water out from underneath it for the next month or two.

Even if this never leads to glacial engineering, it would still be “useful science,” Truffer says. It could answer key questions about how basal water controls a glacier’s movement, improving the models that are used to predict how quickly glaciers will accelerate as temperatures rise.

These experiments would also hint at how many holes might be needed to slow down a massive glacier like Thwaites. Roughly 1 to 3 cubic kilometers of subglacial water flow out from beneath Thwaites each year, according to one estimate. If the holes were strategically placed in an area where the glacier slides over rough bedrock, Tulaczyk speculates that removing just 1 to 3 percent of that water might vastly increase the drag, slowing the glacier. It might mean as few as 10 holes, each with a pump pulling out 100 liters of water per second, which existing well pumps are capable of. At the other extreme, it could mean 100 holes and 10 times as much water.

Other researchers are developing variations on Tulaczyk’s idea. Brent Minchew, a glaciologist at MIT, has suggested that removing heat from the glacial bed would cause the subglacial water to freeze, accomplishing the same thing. He would do this using something called a thermosiphon. Such siphons create a convection current, with warmer gas bubbles constantly rising in a sealed pipe of condensed CO₂ and colder liquid constantly sinking to take its place at the bottom. The heat from the gas bubbles would escape through the top of the pipe and into the environment.

Thermosiphons are used along the Trans-Alaska Pipeline to prevent permafrost beneath the pipe from thawing and sagging (which could destabilize the pipe). They are also being studied for possible use in geothermal power plants to transport heat from several kilometers underground. At Thwaites, thermosiphons would drain the heat slowly over a period of years before the glacier started freezing onto its bed. But that would be enough, Minchew says: “Slow and steady wins this particular race.”

Removing Thwaites’ lubrication was one of two major strategies kicked around at the December 2023 workshop. The second was newer and complementary.

Could we block warm ocean currents that melt glaciers?

The Southern Ocean surrounding Antarctica is known for its rough seas. Nowhere else on Earth can westerly winds circle the globe without encountering land. These winds pile the water into waves that can reach the height of a four-story building and drive the most powerful ocean current on Earth — the Antarctic Circumpolar Current.

The westerly winds are strengthening due to climate change, causing the circumpolar current to intensify and shift south, in toward the edges of Antarctica. As the current ruffles along the perimeter of Antarctica’s continental shelf, the resulting turbulence causes a steady stream of water to billow up from more than a kilometer below the ocean’s surface onto the edge of the shelf. This circumpolar deep water, owing to its high salt content, is several hundredths of a percent denser than the cooler, less salty water on the shelf. That slight difference is enough to guide the warm, dense water into a deep groove called the Pine Island Trough, which dips several hundred meters below the rest of the shelf.

This trough was carved by Thwaites and Pine Island glaciers as they advanced across the continental shelf during the last ice age. Today, the trough provides an easy path for dense, salty water to flow inland and access the fronts of those glaciers.

Though the water that reaches the front of Thwaites is just 2 to 3 degrees Celsius above its freezing point, a vast amount of it flows through, roughly 2,800 cubic kilometers per year. That’s nearly enough water to fill Lake Ontario twice. It delivers 900 billion watts of thermal power to the front of Thwaites year-round — similar to the output of 450 nuclear power plants.

Michael Wolovick thought often about these currents during his early career in glaciology. In 2017, during a postdoc at Princeton, he gave public voice to an idea that he’d been mulling for years. While attending the European Geosciences Union meeting in Vienna, he presented a research poster suggesting that massive dikes built across seafloor troughs like the ones in front of Pine Island and Thwaites glaciers could block warm currents and delay glacial retreat.

The meeting space was huge, with thousands of posters displayed. Wolovick’s was an oddball in a section otherwise devoted to standard measurements of ice shelves and tidewater glaciers. Sometime in the early evening, a scientist named John Moore showed up and introduced himself. He was excited about Wolovick’s idea.

“I didn’t realize that anybody else was working on this,” says Wolovick, now at the Alfred Wegener Institute for Polar and Marine Research.

In March 2018, he, Moore and colleagues published an essay in Nature calling for research into glacial engineering. It drew a sharp retort from seven prominent scientists, who warned that it was a fool’s errand, likely to distract from the ultimate goal of reducing greenhouse gas emissions.

The next September, Moore and Wolovick proposed that an 80- to 120-kilometer-long dike in front of Thwaites could block incoming warm currents by cutting off several branches of the Pine Island Trough. The dike would rise 300 meters above the seafloor, topping out at 250 to 300 meters below the sea surface. Calculations suggested it might stabilize the glacier. But building it would consume 30 to 50 cubic kilometers of rocks, gravel and mud — several dozen times the volume of material moved in the decade-long digging of the Suez Canal.

Among the people who read those papers was Bowie Keefer, an engineering physicist living near Canada’s Vancouver Island. He had worked on desalination, renewable energy and harnessing tides to generate electricity. He loved the idea of blocking ocean currents and contacted Wolovick and Moore to suggest a design more likely to survive the harsh environment.

Anything constructed on the seafloor would be under constant threat from the icebergs that crowd the front of Thwaites. Some are up to 400 meters thick. Their undersides frequently scrape and gash the seafloor. If you build a barrier, Keefer says, “you have to configure it so icebergs can go over it without destroying it.” He imagined something akin to the flexible streamers of kelp that his kayak frequently slid over as he paddled the waters near his home.

In March 2023, Wolovick, Moore and Keefer published two papers in PNAS Nexus rolling out a new design: a series of thin, buoyant sea curtains anchored on the seafloor. The curtains would easily bend as icebergs drifted over, while still blocking the dense, salty, bottom-hugging currents. Keefer imagines a modular design, composed of a couple thousand overlapping panels, each about as wide as a football field, that could be replaced individually if damaged.

Examining the layout of Pine Island Trough and its various seafloor branches, the team plotted four sections of curtain that would protect Thwaites and Pine Island glaciers, as well as several other nearby glaciers. These flexible barriers would top out a little more than 500 meters below the sea surface — just high enough to block the warm bottom currents. But in spots where the troughs are especially deep, that means the curtains would have to reach as much as 250 to 450 meters above the seafloor, equaling the height of the Empire State Building in some places.

The estimated total building cost is $40 billion to $80 billion; on a per kilometer basis, that’s similar to the cost of building some large bridges. Maintenance might cost another $1 billion to $2 billion per year. These costs might seem astronomical at first glance. But they could be small compared with the cost of building and maintaining dikes to protect coastlines from rising seas, estimated at $20 billion to $55 billion per year — every year — if global temperatures rise by 3 degrees.

But there’s some question about whether a barrier might simply redirect warm currents — and thus melting — to other glaciers farther west along the coast. In 2019, Rodehacke and colleagues published a rough analysis suggesting that, for an 800-kilometer oceanic barrier, that might be the case.

Yoshihiro Nakayama, an oceanographer at Dartmouth College, is doing more detailed simulations of how a shorter barrier — a 260-kilometer curtain blocking the main trunk of Pine Island Trough — would impact the region.

Researchers are still considering what building materials to use. Constructing curtains with smooth plastics could allow icebergs to slide harmlessly overtop. But that would release microplastics into some of the world’s most pristine ocean waters — a prospect that Keefer does not welcome.

Rather than a synthetic curtain, Ole Wroldsen, a marine civil engineer with Entr, the consulting arm of the company Aker Solutions in Fornebu, Norway, envisions other potential options, including a net fabricated from natural plant fibers. Over time, it would become encrusted with sponges, corals, mollusks and other marine animals, increasing its ability to block currents. The goal is to create a living structure “that is acting with nature rather than against nature,” he says. “That would be a perfect match.”

The first curtain-related field tests could start in a year or two — once private funding is arranged. A series of small, 10-meter-long curtains built with different materials could be rooted in a Norwegian fjord, then monitored to see how quickly they deteriorate. Larger versions might later be installed, temporarily, in a glacial fjord in Greenland or the Arctic archipelago of Svalbard, to study the impacts on ocean currents.

But even if these small field trials succeed, other political and societal challenges lie ahead.

Glacial engineering could have global side effects

Lessons from another type of geoengineering suggest that glacial engineering is likely to encounter opposition. For two decades, scientists have used computer models to study the idea of injecting millions of tons of sulfate aerosols into the stratosphere to reduce warming from the incoming sunlight.

Proponents see sulfate aerosols as a way to forestall climate catastrophe for a century or two, giving humans time to stop emitting CO₂ and remove it from the atmosphere. But because of concerns about unintended side effects, researchers have not succeeded in getting a single field study off the ground. Many people distrust the notion that a handful of wealthy nations — having already messed up the planet by emitting greenhouse gases — will now fix the problem for everyone by messing with the planet some more.

Glacial engineering is far more targeted, geographically, than stratospheric aerosols. But it still may have unintended effects.

Sharon Stammerjohn, a sea ice scientist at the University of Colorado Boulder, believes that sea curtains, for example, might cause turbulence that mixes deep, warm water into the upper layers of the coastal ocean. The extra warmth could result in less sea ice production in those areas, she says.

A drop in sea ice could disrupt the interplay among photosynthetic plankton, which depend on the melting ice in spring and summer, the krill that eat them, and the penguins and whales that eat the krill. “There’s winners and losers,” says Stammerjohn.

Pettit does not distrust the intentions of people like Tulaczyk, whom she has known for decades. But she and some others are uncomfortable with the idea that at least in the near term, glacial engineering research might be funded, in part, by billionaires from Silicon Valley. She worries whether they will have the humility to refrain from steering the research toward their own preferred outcomes. Any money should have no strings attached, with groups of scientists reviewing and deciding which experiments will be funded, she says. “If this is going to happen, we need to make sure there’s some reasonable heads involved.”

There’s also concern that a strong move toward glacial engineering could upset the delicate geopolitics of Antarctica. It is by far the largest piece of land on Earth that is not owned by a particular nation. Though various countries made vast, overlapping territorial claims on the continent during the mid-20th century, the signing of the Antarctic Treaty in 1959 put these claims on hold. Countries pledged to limit their Antarctic activities to scientific research.

But tensions persist, says Klaus Dodds, a professor of polar geopolitics at Royal Holloway, University of London. The stations maintained by over two dozen countries there don’t merely serve science: They maintain a national presence in Antarctica, allowing those countries to have a seat at the table if the continent is ever divvied up.

“The Antarctic is already in quite a precarious state at the moment, geopolitically,” Dodds says. He believes that any serious glacial engineering effort would be undertaken by a small group of allied countries — say, the United States, the United Kingdom, Australia and New Zealand, or perhaps Russia, China and India. It would involve creating new infrastructure on the continent, and this could be viewed as a thinly veiled land grab, he says.

Construction in Antarctica presents logistical challenges

If glacial engineering turns out to be scientifically and politically feasible, its ultimate fate will hinge on the ability of humans to build large and complex structures in an area that is notoriously harsh, even for Antarctica.

Thwaites Glacier sits midway along a 7,000-kilometer stretch of coastline (roughly the distance from Seattle to Quito, Ecuador) without a single permanent outpost. No human laid eyes on the glacier’s ice front until the 1940s, when a U.S. naval plane flew over. No human stood on its heavily crevassed ice shelf until 2019, when a plane first landed. And although heavily armored icebreakers began plying Antarctic waters in 1946, not until 2012 did an icebreaker come within sight of Thwaites Ice Shelf. Even today, the icebreakers that are sent to conduct research have a 50-50 chance of getting there any given year.

The region owes its extreme inaccessibility to a quirk of geography that causes ice to pile up. During winter, sea ice up to 1.5 meters thick often extends more than 600 kilometers off the coastline. As the ice breaks up in spring, strong winds gather the ice and push it into the bay where it is compacted and piled up to 10 meters thick in some places. That jumbled ice might continue drifting west, but it’s stopped by a submarine ridge that extends 100 kilometers off the coast just west of Thwaites.

Hundreds of icebergs run aground on that ridge, creating “a huge log jam,” Stammerjohn says. The stacks of sea ice and iceberg fragments the size of small apartment buildings pile up behind the bergs. The area in front of Thwaites and Pine Island is often choked with ice, even in summer.

A powerful, agile icebreaker working in this environment often has to abandon planned operations. That’s because simply lingering for 20 hours in one place, to launch a submersible or drill a core from the seafloor, is sometimes too risky amid the drifting sea ice and hundred-million-ton icebergs. But a ship towing a 1- to 5-kilometer-long segment of preassembled sea curtains would present a much larger, and less nimble, target for drifting bergs. Workers would rush to lower the new curtain and cinch it to the seafloor over a period of several days, as the crew anxiously monitored the shifting ice.

People working 30 to 100 kilometers inland from the coast, drilling through Thwaites Glacier to pump out water, would face different challenges.

Subglacial water would have to be pumped from the boreholes year-round, transported through hoses and misted into the air to create snow that would settle harmlessly on the glacier’s surface. The entire system would require constant heating, to prevent the kilometer-deep, water-filled holes from freezing shut — and to prevent water inside the hoses and pumps from freezing and rupturing the equipment. The power requirements for pumping 1,000 to 10,000 liters of water per second could range from 480,000 to 4.8 million watts — similar to the electricity consumption of 400 to 4,000 American households.

“Solar power is not an option” during the long, sunless winter, Truffer says. Wind turbines are used in some parts of Antarctica — and five to 50 of them could probably supply the energy for pumping Thwaites Glacier — but they would have to be built to survive hurricane-strength gales. If the power were generated by burning diesel on the other hand, it could require 260,000 to 2.6 million gallons of fuel per year, enough to fill as many as 250 semi tanker trucks.

This might sound like a ridiculous amount of pumping and energy. But it’s a mere drop in the bucket, representing no more than 2 percent of the water pumped from all the wells in California each year — and a tiny percent of the energy used. Its main significance is that it would require major logistics in a remote region.

Hundreds of thousands of kilograms of food, gear and potentially fuel would likely be delivered annually by an icebreaker to an accessible spot on the coastline, 1,000 kilo­meters northeast of Thwaites. Supplies would be loaded onto convoys of shipping container–sized sleds and towed by tractors, traveling on routes carefully surveyed for crevasses, which the British Antarctic Survey often uses in this region.

Constant snowfall would bury pumping equipment. Alternating thaws and cold snaps could permeate the snow with layers of rock-hard ice. The machines would have to be dug out yearly with chainsaws, or mounted on stilts that could be raised above the new snow each year. The operation “would be extremely massive,” Truffer says.

In Robinson’s novel, scientists eventually use engineering on 30 glaciers. But the real-world scientists imagine targeting no more than a few: maybe Thwaites alone, maybe also Pine Island Glacier, and if things continue to worsen, maybe a couple of others in East Antarctica. If you had to protect glaciers around the whole continent, it’d be simpler to build seawalls around cities instead.

 The “key benefit of glacial geoengineering is that you can do this in a very limited geographic area and get big bang for your buck,” MacAyeal says.

For Tulaczyk, now 58 years old, it has been a long journey since those early days. After the sharp rejection on his funding proposal, he decided to put glacial engineering on the back burner for fear that it would endanger the funding of his other research. But now, “I’m going to retire,” he says. As a result, he feels more free to speak openly. “I want to stick to this issue.”

He’s pleased to see younger scientists like Wolovick and Mankoff also getting involved. They might live long enough to see the results, he says. “For a young scientist to be doing this, when they’re trying to start a career, while there’s so much hostility,” Tulaczyk says, it’s “amazingly courageous.”