Ice sheet river, summer 2006 (Sarah Das/Woods Hole)
16
Meltwater Season
On some days, Holland liked to say that he was working on “one small piece of the Greenland puzzle.” And no doubt it was true. Walking through Kangerlussuaq airport on a spring or summer morning, there were now so many researchers coming and going that it seemed the Greenland puzzle was far larger than anyone had previously imagined. Long ago, Robert Peary had called the island’s frozen regions “the eternal ice.” But any reference to the island, in the press or on television, seemed to carry the warning that Greenland is melting.1 Perhaps this surprised the general public; to those watching the big melt up close, any sense of astonishment about the ice sheet’s demise had long since passed.
Many of the scientists coming to Greenland were there to gather observations about the ice and make computer models more accurate, so that the future could be projected with greater confidence. Some, like those in David Holland’s group, were passing through airports on their way toward any one of the hundreds of glaciers along the island’s coasts. Others, such as J. P. Steffensen and Dorthe Dahl-Jensen, were leading international teams drilling deep cores out of the center of the ice, both to better understand the ice sheet’s flowing movements and to fine-tune their historical knowledge of Greenland’s climate. On a sunny morning at Kangerlussuaq airport, you could sometimes see Steffensen, smoking a pipe and driving a front-end loader, bringing coolers of ancient ice cores to a plane heading back to Copenhagen.
But there were so many others, too, arriving for meltwater season—scientists mustering supplies to camp on the ice sheet and measure water pooling along its surface, for instance, or to gauge streams rushing into moulins, the deep holes in the ice sheet that bring water into secret plumbing channels thousands of feet below. In the local cafés, you could meet glaciologists, hydrologists, anthropologists, geomorphologists, and sedimentologists. Greenland was like Los Alamos in the 1940s, the small city in New Mexico that served briefly during World War II as the nexus for all subatomic knowledge, except here it was all about the science and impacts of lost ice. You might chat with marine biologists studying the survival habits of narwhals and polar bears in a changing habitat; or you might discuss ancient history with archaeologists who happened to be digging into the remains of Norse ruins in the southwest. The latter were racing to finish their work before the permafrost that preserved those remains melted and the artifacts deteriorated. If and when that happened, the historical clues to the Norse disappearance in the 1400s might vanish forever.
All of these research projects, conducted between 2014 and 2018, happened to coincide with the hottest years ever recorded on earth. But in Greenland, the rise in temperatures was even more acute than rising global averages implied. Much as climate models had predicted, the Arctic regions appeared to be warming at twice the rate of the rest of the world. In June 2016, a visitor could relax outside in a T-shirt and shorts in Nuuk, Greenland’s capital city, previously known as Godthab, where it was warmer—75 degrees Fahrenheit—than in New York City. The winters in Greenland were becoming more temperate, too. At the National Oceanic and Atmospheric Administration—NOAA, the U.S. agency that monitors the weather and oceans—scientists summed up their annual observations for 2017 by noting that “the Arctic environmental system has reached a ‘new normal.’ ” The region now appeared to be in a permanent state of decline, with thinner snow cover, steady reductions in the mass of ice in the Greenland ice sheet, and dramatic losses in sea ice in the Arctic Ocean. In fact, over the past three decades, the sea ice cover had been reduced in area by about half—and less ice, in turn, meant that darker and more open ocean waters could absorb more sunlight. That change would melt the ice even more, and thus bring even more heat into the region.2
It was a painful feedback loop. And it seemed that no place in the north would be immune to the seeping warmth. In February 2018, at Cape Morris Jessup, a weather station at the northern tip of Greenland, instruments registered daily temperatures 45 degrees Fahrenheit above normal. Seeing as the station was only four hundred miles from the North Pole and was shrouded in the constant dark of Arctic winter, the news left many of the world’s meteorologists dumbstruck. “The Arctic is the world’s cooling system,” a Finnish official, Stefan Lindstrom, remarked not long after. “If we lose the Arctic, we lose the world.”3
To experts on the region, the “new normal” had the air of an encroaching emergency.4 The loss in Arctic sea ice and the jumps in Arctic temperatures were so drastic that it seemed reasonable to begin asking whether abrupt climate changes, observed in ice cores extracted from the center of Greenland’s ice sheet in the early 1990s, were showing up again today. “If you look at the modern warming of the Arctic, in a five-year period from 2007 to 2012, we see a doubling of the length of the summer in the eastern Arctic, and that is equivalent to a 5° centigrade rise in temperature in less than five years,” says Paul Mayewski, who had been in charge of the GISP-2 drilling project twenty-five years before. “There is no doubt that that is an abrupt climate change event.” Mayewski pegged these shifts to significant alterations in atmospheric circulation. But he saw the trend as “the first trigger in a series” of climatic changes that would in time migrate to other areas of the Arctic.5 In early 2018, a series of academic papers called attention to evidence that ocean circulation patterns in the North Atlantic Ocean around Greenland were slowing, too, with potential devastating effects. These included higher sea levels on the East Coast of the United States, alterations in seasonal weather patterns, disruptions in fisheries, and more intense storms. Climate models had long predicted the slowdown in circulation as a potential risk for a hotter planet. “I think it is happening,” Stefan Rahmstorf, of Germany’s Potsdam Institute for Climate Impact Research, told The Washington Post. “And I think it’s bad news.”6
In Greenland, many Inuit seemed to think they would be able to withstand the switch in weather and sea levels.7 They explained to reporters that they had lived in the world’s harshest environment for nearly a thousand years, and that they would endure far longer than the rest of us. The melting ice and shifting climate had been obvious to them for decades already. Harbors that had been iced in for six months a year—harbors once so impenetrable they had delayed Alfred Wegener for weeks and led indirectly to his death—were suddenly navigable through the year, which had the positive effect of boosting the local fishing industry. The retreating ice sheet had exposed areas of new land in the south that for a decade had been attracting the interests of mining companies, intent on digging for gemstones and rare earth metals. A few intrepid souls, also in the south, had been trying their hands at agriculture—growing strawberries, in one instance—in a country where the climate had historically destroyed the lives of those who could not hunt.
Still, the local traditions were in jeopardy. On an April afternoon near Thule, just a few hundred feet from Rasmussen and Freuchen’s old trading station, a hunter named Sofus Alataq, dressed in a hooded sweatshirt and Adidas warm-up pants, came through the snow with his dog team. He lived in Qaanaaq, the northernmost town in Greenland, which had been set up by the U.S. Army during the construction of Thule Air Base in the 1950s. Alataq’s sled was laden with clothing, rifles, and polar-bear furs, which he used for warmth in extreme cold. But in English, he said with disappointment that most of his hunting season had been for seal, not bears, and that recent changes to the climate had made sledding on the frozen bays and fjords more difficult. “Less ice, warmer weather, spring is sooner,” he explained.8
In Ilulissat, the coastal town near Jakobshavn Glacier, another hunter from Qaanaaq, Toku Oskima, put it slightly differently. She explained that the changing weather had made it more difficult to preserve meat in caves; and every winter, the thickening of ice along the coasts happened later and slower, therefore limiting the days she could take her sled out. She seemed confident she would adapt. But Oskima said, “The warmth of the sun is getting heavier.”9
Every year, about half of Greenland’s ice losses happen on the edges, through glaciers like Jakobshavn. But another half is lost through melting on its surface.10 This melting comprises turquoise lakes and rushing aquamarine rivers and thin lapis creeks. Unlike the island’s biggest glaciers, we already know a fair amount about how much the ice sheet’s surface is warming. For nearly thirty years, a Swiss scientist named Konrad “Koni” Steffen has been taking readings on temperature, wind, solar radiation, and melting at a station known as Swiss Camp, on the central ice sheet. Located about fifty miles east of Jakobshavn’s calving front, Steffen’s camp has weather towers that collect data on the surface environment several times a minute; the information is then transmitted to him in Europe and the United States (he has offices in both Zurich and Boulder) every hour. But the observations aren’t limited to one location. Over the past few decades, he has set up a system of eighteen installations around Greenland that measure weather on the ice sheet. Every spring he checks on these towers by setting out from Swiss Camp, moving from one site to another either by snowmobile or by turboprop. “It is really by chance that I ended up studying the ice sheet,” he says. In 1990, he was planning to conduct a study on glaciers in Tibet, but the Chinese government wanted to levy high charges on his science team. Steffen thought the costs were unreasonable, so he pulled out, and that led him to try Greenland. He built a camp that year on the ice sheet at an elevation of about thirty-eight hundred feet—several permanent, thickly insulated tents set on a large plywood platform. And then he began to monitor the environment.
Steffen is the modern era’s equivalent of Carl Benson, the scientist who in the 1950s went driving around the ice in a weasel, digging snow pits to measure conditions on the ice sheet. “He is my model,” Steffen remarks, noting that he met Benson in Alaska in the 1970s and sometimes consults his old papers from the Army Corps of Engineers, where Benson recorded accumulation rates and melting around the ice sheet. One difference in the work of the two men is that Steffen has reaped the benefits of GPS and electronic sensors. Another is that Steffen has experienced changes in the ice that Benson could not have imagined. In the early 1990s, Steffen recalls, “we almost lost the camp because we got too much precipitation.” The tents were buried by snowfalls, so he had to enter through the roof. “It was only in the year 2000 that the surface started to go lower down,” he says, but that year marked a steady and unrelenting downward trend. His plywood platform and tents collapsed several times as the ice sheet continued to melt and plummet in elevation. It was like going on vacation and returning home only to find that the floor of your bedroom had dropped by several feet, and that your possessions and bedding were now in shambles. In the wreckage of tents and equipment at Swiss Camp, Steffen was witnessing the same changes in ice sheet elevation that IceBridge and ICESat were measuring from above.
He and his students rebuilt the camp twice, driving foundational supports deep into the snow and ice to future-proof the platform. But in time, as the ice sheet continued to melt and thin underneath the station, the supports were exposed. If you happened to be flying low on NASA’s IceBridge mission during the months before the summer heat turned the landscape to slush, Swiss Camp appeared like a tiny oil drilling platform, sitting atop stilts in a vast ocean of white. By 2017, Steffen’s measurements indicated that the ice had declined by nearly forty feet at Swiss Camp since he arrived, and the trend lines for the future prompted him to put the camp up for sale for one dollar.11 He didn’t really expect a buyer. Even if someone wanted to, there was no easy way to get to Swiss Camp except to ski there, as Nansen might have done—or to fly there, in a helicopter that costs five thousand dollars per hour, from the nearby village of Ilulissat. So the sale price became a joke that Steffen liked to tell at lectures. He meanwhile began making plans to move the camp to higher elevations on the ice sheet—perhaps thirty or forty miles farther in, where it would be situated in a colder and more stable region.
At this point, it was hard to imagine Greenland without Swiss Camp. The station over time had become a destination spot for visiting dignitaries seeking to find a kind of ground zero for global warming; Al Gore had been there, along with so many journalists, politicians, and European princesses and princes that Steffen could barely list them all. The true value of Swiss Camp was in the growing record of observations, however. Steffen calculated that between 1990 and 2018 average temperatures on the ice sheet had increased by about 2.8 degrees Celsius, or 5 degrees Fahrenheit. Over the same time period, the total area of the Greenland ice sheet that was vulnerable to surface melting had increased by around 65 percent. Carl Benson would barely have recognized the place.
In talking about the melting in Greenland, glaciologists sometimes like to describe the relationship between rising temperatures and diminishing ice with mock simplicity: “When it gets hotter,” they say, “ice melts.” And yet the surface of the ice sheet has turned out to be far more complex than it once appeared. In recent years, studies have observed that meltwater from the ice sheet doesn’t necessarily run off Greenland into the oceans; occasionally it stays in the firn, trapped like water in a huge sponge. In 2013, a team of scientists even discovered an aquifer under the snow in east Greenland, containing extraordinary reserves of water that covered an area the size of West Virginia. Conceivably, the water could be released quickly, in a flooding gush, in the near future.12
In sum, the ice surface is beset by a variety of forces brought on by changing climates. The surface is getting darker, for instance, thanks to a combination of industrial soot, dust, microorganisms, and algae, which have settled upon a “dark zone” on the ice sheet’s western region. This dust, black carbon, and biological life now form an ecosystem that flourishes during the warmer months.13 But the danger is that the darker Greenland’s ice gets, the more solar energy it absorbs. And the more solar energy it absorbs, the more it melts and the darker it gets. This feedback loop is known by glaciologists as the albedo-melt loop (albedo is a measure of surface reflectivity).14 And unfortunately, it is reinforced by another self-perpetuating process. As Greenland’s ice sheet melts and drops in elevation, just as it has at Koni Steffen’s Swiss Camp, its ice becomes more vulnerable. Lower altitudes enjoy warmer temperatures; they allow lakes to creep farther up the ice sheet with each passing decade. Therefore it now appears that the more Greenland melts, the more Greenland melts.
At its current pace of erosion, Greenland’s ice sheet adds about one millimeter of water every year to the world’s oceans; at this rate, the ice sheet could last seven thousand years. Yet no glaciologist in the world seems to think this will be the case. An astonishing study published in December 2018 concluded that the ice sheet was now melting faster than at any time for at least the past 350 years, and that the “nonlinear” response of the ice to warmer temperatures would lead to “rapid increases” in Greenland’s sea-level contributions.15 With its mellifluous, singsong Swiss accent, Koni Steffen’s voice tends to soften the bleakness of his outlook. Yet in his reflective moments, he predicts the melting ice over time will lead to a painful migration of 300 to 500 million people, globally, away from the coast.16 “Greenland isn’t pausing at 2100,” he says. “It continues like this, the warming. And it gets worse and worse. Most people think we can model until 2100, and that 2 degrees centigrade is not so bad. But it won’t stop there. And the melting won’t stop there. The curve gets steeper, and steeper, and steeper.” One evening in Greenland, he says darkly: “There will be a change coming, and obviously a change that we have not seen in thousands of years.”17
In 2012, a glaciologist at the University of Colorado named Tad Pfeffer wrote a magazine article entitled, “Glaciology Needs to Come Out of the Ivory Tower.” His main point was that his profession had found itself in an unlikely situation: “What happens when a field of scientific inquiry that starts out as a subject motivated purely by curiosity and driven by the simple desire to understand how the world works, is turned rather suddenly into a field with applications of the most urgent nature?” Pfeffer observed that what he and his colleagues were now doing—trying to project what would happen to ice sheets, as well as how much (and how fast) sea levels could rise—was crucial to untold millions of people. With their research redounding far beyond obscure academic journals, glaciologists had now become “stewards of the land.”18
To be sure, some glaciologists already understood the stakes. Their most difficult challenge was trying to come up with an accurate projection for the near term—that is, a number by which sea levels might rise in the next few decades—and to demonstrate confidence about how the ice sheet melt might also affect, say, ocean circulation patterns. Contrary to many assumptions, climate scientists don’t hold the conviction that computer models of the future suggest concrete reality. Often, they like to quote a British statistician, George Box, who in 1978 remarked that “all models are wrong, but some are useful.” In truth, many computer models—such as ones done in the late 1960s and early 1970s by Syukuro Manabe—have proven nearly correct about warming trends, even if they haven’t shown the same precision about ice sheets. But the larger point is that good models, especially those that build into their codes the latest discoveries and observations, can provide a general sense of what can happen. And in any event, coastal planners, economists, politicians, and ordinary homeowners aren’t usually curious about the mechanisms of calving glaciers or moulins; they don’t tend to worry about dark algae blooms spreading like an illness over the westernmost regions of the ice sheet. But they do desire knowledge of what the world will be like in the future. For those reasons, the endpoint of the century—the year 2100—has increasingly become a benchmark for the climate community. It seems to offer a practical guideline for, say, engineers, and how they might design infrastructure and buildings. In a more conceptual sense, the date signifies the end of the lives of our youngest children and grandchildren. A computer projection of that year is therefore a sketch of a world that they will—most likely—live long enough to glimpse.
As far back as the early 2000s, Eric Rignot was thinking about the difficulty of predicting this kind of future scenario for the ice. Rignot had grown up in France, near the town of Chambon-sur-Lignon, in a rural, mountainous region of cold winters and crystalline air. Early on, he was captivated by stories of the Arctic, and in particular he loved Jules Verne’s novel The Adventures of Captain Hatteras, the story of an intrepid polar explorer who travels to the North Pole only to find an ice-free region and a volcano. Published in 1866, the story predated not only Nansen and Peary, but other explorers who actually made it to the pole.
The contrast with Rignot’s career is curious. His work involves the risk-taking of an explorer, and his accomplishments in research—with NASA’s Jet Propulsion Lab and the University of California, Irvine—demonstrate an intention to make observations in some of the world’s most treacherous places. He has a luxurious French accent but is not a romantic. Rignot’s goals are to challenge assumptions about the world’s ice sheets and to speak volubly of the dangers of collapse. “My long-term objective is to try to come up with ways we can put upper bounds on these changes—upper bounds on how fast the ice sheets could change, and how fast sea level could rise,” he explains. “If we can get there and tell people, ‘Look, it’s going to be very hard for nature to go faster than this,’ I think I’ll be able to say we got our job done. Nobody will come back in fifty years and say, ‘You guys were just so conservative and you did a big disservice to society by giving this conservative view on everything.’ No, you actually pushed it, and reality maybe is going to fall a little bit below that.”19
To find an upper bound for ice sheet collapse—that is, the worst scenario that current data and the laws of physics could allow—requires a combination of things. You need years of field observations, reams of remote sensing and geologic information, and a deep knowledge of feedback mechanisms. As Rignot points out, every glacier in Greenland and Antarctica is unique, and to predict their future behavior requires observing the individual characteristics—width, depth, bedrock characteristics, seawater exposure—of each. You need ample funding, the best computers and coders for modeling, and a willingness to stick to the objective for years. You need imagination, too, so as to contemplate things that we know happened in an era before the advent of recorded human history, when ice sheets collapsed and sea levels rose catastrophically.
For an upper bound, it might not help to think in a straight and logical progression; you have to be willing to think in terms of climate surprises, rapid jumps or unexpected slowdowns, nonlinear changes. You need to make a guess as to whether or not human society is capable of altering how much carbon dioxide it puts into the atmosphere over the next few decades. You also need to ponder whether melting permafrost, the frozen soil of the Arctic, will hasten the escape of methane, a gas far more intense in its heat-trapping characteristics than CO2, and whether that will play a large role in influencing future weather. Ultimately, you are boiling down thousands of systems of immense complexity—systems of ice, water, rock, and air; systems that are natural as well as human—into a single data point of surpassing density, simplicity, and urgency.
For the calculations, the first thing to consider is how hot it will be in the future, since warmer temperatures will expand the oceans by a significant amount. This is not especially difficult, since a number of climate models already exist that have proven fairly accurate for different carbon emission scenarios. The second thing is to evaluate the fate of the world’s melting inland glaciers—in the Alps, North America, South America, and the Himalayas. Those add to sea levels, too. A third thing involves a consideration of how much water the ice sheets will lose, on net, by melting and evaporation on their surface, a process that will likely be closely linked to future temperatures.
After that the calculations get much harder. Like David Holland, Rignot believes that ice sheets can lose large amounts of mass very quickly by way of big glaciers that end at the ocean. Also like Holland, Rignot doesn’t think our models yet explain the future behavior of those glaciers. He, too, has long been worried about West Antarctica’s Thwaites and Pine Island glaciers. In 1998 he published some of the earliest studies on their retreat—“I think at that point I realized, we are onto some big changes,” he says—and fifteen years later he was among the first to declare the region might have reached a point of “unstoppable” collapse. In Rignot’s view, “We’ve started a process here which is not easy to reverse.” His assessment is that West Antarctica could—could—add several feet of sea level to projections for the year 2100. “I think what we’re seeing in the ice sheets is a collapse,” he says. “It’s just that we don’t realize the time scales. It’s like looking at a glacier. Does it look like it’s moving? Then you speed up things by twenty times, and it looks like a river. If you look at the changes in the ice sheet in the last twenty years you say, this is going on pretty fast, and it’s only the beginning. So, what’s next?”
The upper bound encompasses not only Antarctica but Greenland. In 2008, Rignot began renting a boat and going up and down the Greenland coast, threading in and out of the network of fjords where glaciers that flow from the ice sheet terminate at the water’s edge. He was trying to assess what is known as the bathymetry of these regions—the depth of waters in the fjords and how ocean temperatures and salinity might accelerate the melting. The work was tedious, difficult, and not always safe. “It was unpleasant,” Rignot acknowledges, adding that he also saw it as necessary, since it had never been done before. Much of the time he and his colleagues were pushing huge chunks of floating ice out of the way with poles so he could get good instrument readings. “At first we used a small fishing boat—not a very sturdy boat,” he recalls. “We had a lot of problems with that boat. It was too old. Every year something bad was happening to it. Eventually I had a bit more money, and we got a bigger boat, and then we started mapping the sea floor.” In time, the data led to the conclusion that the fjords often went much deeper than had been previously assumed, and that the glacier fronts were more vulnerable to melting and retreat. In conjunction with IceBridge data, a more detailed picture of Greenland’s future came together for him. His vision for the island is often at odds with the consensus that Greenland will melt slowly into the future. As he sees it, the great danger is that warming ocean waters in the Arctic can melt glacier fronts far faster than warming air. This poses a threat to some of the largest glaciers in Greenland—“the big guns,” as Rignot calls them, which include Jakobshavn on the west, and several others in the north. Like tunneling animals, these rivers of ice have over time gouged deep canyons, and these canyons go all the way back into the central basin of the ice sheet. That means that even as such glaciers retreat, warming waters will follow them, and as they retreat into the canyons, they may continue to melt.
“So, these are the weak points of Greenland,” Rignot says. “And it’s not like we’re looking at the big taps opening up in the next century. They’re going to be opening up in the next decade or so. And after that it’s going to be really hard to slow it down.”
There happens to be a consensus estimate for global sea level rise in 2100—between a half meter (1.6 feet) and a full meter (3.2 feet). The numbers were put forward by the IPCC, the Intergovernmental Panel on Climate Change, which is made up of leading scientists around the world. Rignot considers the IPCC numbers too conservative. At the moment, he thinks one and a half meters (or about five feet) of sea level rise is more likely, but also that the upper bound is not yet quantified and may be higher. This may not become clear until observations and models are improved over the next decade or two. “But with sea level rise, we’re not talking about something that is going to happen down the line,” Rignot remarks. “The changes are taking place right now, and some of these changes are very significant. And we did not expect them so soon. So, wake up. Sea level rise is real. It’s three millimeters per year right now. And people say, ‘Oh, that’s only three centimeters per decade.’ But you’re teasing a giant here. And there is no red button to stop this. What is going to happen by 2100 with the ice sheets is, in my opinion, already locked in. There’s not so much we’re going to be able to do to change that.”
Still, for someone who focuses on the most dire possibilities for the ice sheets, Rignot is not hopeless. He likes to point out that the world doesn’t end in 2100. And he thinks it’s possible we will slow the process of collapse in West Antarctica or Greenland, as long as we move to reduce carbon emissions in time. “I think it’s probably in human nature that we’re going to react once we have our back to the wall,” he remarks. But even the “one-meter-plus” by 2100, which is not necessarily the upper bound and may be too low, is problematic. The United States alone has more than 88,000 miles of shoreline; roughly five million people and 2.6 million homes are situated less than four feet above high tide. “With one meter of sea level rise,” Rignot says, “San Francisco airport is under water, and Oakland airport is under water. So, San Francisco doesn’t have an airport? What is the impact of not having an airport in San Francisco?”
It’s unthinkable to him. “But the last time I checked,” Rignot adds, “nobody was building an airport higher up.”20
It may be the case that the collapse of some glaciers in West Antarctica and Greenland is unstoppable. But for the moment there is great uncertainty when it comes to the ice sheets. It may take one hundred years or three hundred years or five hundred years for some glaciers to fall into the ocean, due largely to the way they will break, sliding backward in the process, sometimes pausing for years or decades on a bedrock bump, as sea waters around and underneath them warm. In any event, amongst glaciologists there seems a consensus that the situation is urgent now, even if it isn’t yet at the point of being catastrophic. “We’re not positive if we’ve already triggered it or if we’re really close,” Richard Alley says of a West Antarctica collapse. “I think almost everyone would agree that it’s either one or the other.” But Alley also thinks that if we have committed to losing West Antarctica, “Greenland just became way more valuable.”
This can require a bit of explanation. It’s largely due to the fact that Greenland’s ice sheet sits within a bowl and is ringed by mountains, just as Wegener’s expedition discovered almost a century ago. Even with its deep glaciers, the losses of ice are constrained to a certain degree by the island’s geography, and by the limits in how glaciers can only push ice into the sea by threading through narrow mountain passes. That isn’t to say that Greenland couldn’t contribute many feet of sea level rise over the next few centuries. But with Greenland, says Alley, “we have a little more leeway.”21
The summer temperatures of the Arctic are already too warm for Greenland’s ice to endure. “At some point we will stick our nose beyond the mean annual temperature that is survivable,” Alley explains. And at that point it would be difficult to stop the melting and the feedback loops, as the ice sheet got increasingly thinner and lower in elevation—a criterion for collapse. “We may be pretty close to that; or we may have a few degrees yet,” he says. “But if we stuck the temperature up, and we pulled it back down in a very few decades, Greenland wouldn’t have time to thin enough to destroy its ice.” In terms of sea level rise, that might mean—in the United States at least—that we lose Miami but save New York. Alley says, “Rather than being the end of the world, West Antarctica would just be the huge wake-up call.” Then humanity’s attention would have to turn to saving Greenland’s ice.
Of course, there remains a more difficult question: How is it possible to get society to “pull” temperatures down in a few decades, before it’s too late? Nature might buy us a little time. Even in a steadily warming world, climate can vary over the course of a few years. Greenland sometimes is subject to the weather that recalls its distant past, including big snowfalls (in 2018) and cold summer snaps. These events can slightly replenish the ice sheet and can even lead to temporary advances in some glaciers. What’s more, if ocean circulations change, and the warm water flowing from the tropics to Greenland decreases, colder water may slow the disintegration process of some outlet glaciers.
There may also be solutions that fall under the description of geoengineering. We may develop technological means to remove atmospheric carbon in the future—sucking it in through machines, and then burying it, for instance. Applying such technologies could conceivably delay the worst effects of climate change, though so far doing so on a scale with any significant impact remains untested and unproven. Another idea, now in a testing phase, involves shading the earth, and thereby cooling it, by dispersing an umbrella of atmospheric sulfate particulates, so as to emulate a volcanic eruption.22 Meanwhile, a few scientists have suggested a radical engineering project: damming the Jakobshavn ice stream—effectively building a wall in front of the glacier and blocking warm ocean water from reaching its deeper levels—so as to slow sea level rise.23
At the moment, however, the only permanent solution to impeding rising sea levels seems to be reducing carbon emissions by burning less and less fossil fuel. And even with the unceasing efforts of an expansive network of climate activists, so far the progress is slight. The signing of an international climate agreement to limit atmospheric emissions, conducted in Paris in 2015, seemed a significant step in the right direction, but in 2017, CO2 levels actually rose faster and higher than any time in recorded history. That same year, the United States—the world’s largest emitter of greenhouse gases, along with China—declared under President Trump that it was “getting out” of the Paris Agreement. Somehow, the idea that the continued existence of the world’s coastal cities will depend on collective and political actions over the next few years, and not the next century, has failed to spread wide enough, deep enough, or fast enough.
To meet the Paris Agreement goals, which attempt to limit average global warming to 2 degrees Celsius, “the wealthier parts of the world would need to be zero carbon energy by about 2035,” Kevin Anderson, a climate scientist at the University of Manchester, explains. “And the poorer parts, including China, would have to deliver zero carbon energy by about 2050. And by that I mean everything—cars, planes, ships, industry, all of the energy would be zero carbon by 2050, globally, for us to have a reasonable chance of the two-degree framing of climate change.” It’s not that we lack the technological tools, Anderson says. It’s that the enormity of the task, and the sacrifices involved, haven’t yet sunk in. “I think it will be hugely challenging,” he adds.24
And yet the alternative—not to try or achieve the goal—would be dire.
In reflecting on the work he did in Greenland in the early 1990s, Richard Alley, who toiled in the GISP-2 trench in the center of the ice sheet, sees several deeper meanings in the ice-coring project. “It demonstrated the absolute reality of abrupt climate change,” he notes, which was immensely important to our scientific understanding of climate history. “By knowing about abrupt climate change, and by knowing about the craziest stuff that’s out there, in some bizarre sense we have gained a much stronger understanding of how big an experiment we humans are conducting on the climate.” Alley often lectures on how CO2 is the immensely powerful “control knob” on our climate. These cores, he adds, and the climate changes registered therein, present an even stronger sense that in the steady climb of atmospheric CO2, “what we are doing is really a big deal.” The ultimate results of our actions, in other words, might not only be severe. They might be sudden, too.
Still, one conclusion Alley has drawn from the ice cores is not really about any scientific discovery. It’s a note of historical optimism that we might keep in mind when we think about reducing carbon dioxide emissions. Amongst all the trace gases and chemicals analyzed in the Greenland ice cores, a clear residue of lead showed up in certain segments. A few thousand years ago, for instance, Alley notes that “you can see the little blip of the Romans.” This would mean the residue of ancient smelters, in Spain and elsewhere, which the Romans used to burn ore to render silver. The process released lead into the air as a by-product, which eventually was deposited in snow that fell on Greenland. In more recent cores, Alley says, we can see lead traces from the fumes of the industrial revolution, which began in the late 1700s. And then eventually, in cores from the twentieth century, the unmistakable fingerprint from leaded gasoline comes through.
And yet, something interesting happens in the 1980s. Lead traces in the ice mostly disappear. “We turned it off. We cleaned it up,” Alley says, pointing to the switch in automobiles to unleaded gasoline after lead was banned by environmental regulations. “And the world didn’t end, and the economy didn’t end. And you can’t look back at economic data and find a horrible disaster that happened when we decided we didn’t want to poison ourselves with lead.”
He pauses and then adds, “It’s so beautiful, so clean in the ice core records. And you can just see: This lead is human caused. And then you see: This is when humans decided that we didn’t want to do that anymore.”