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56 THE NEW YORKER, APRIL 25, 2005

ANNALS OF SCIENCE

THE CLIMATE OF MAN—I

Disappearing islands, thawing permafrost, melting polar ice. How the earth is changing.

BY ELIZABETH KOLBERT

The Alaskan village of Shishmarefsits on an island known as Sari-

chef, five miles off the coast of the Se-ward Peninsula. Sarichef is a small island—no more than a quarter of amile across and two and a half mileslong—and Shishmaref is basically theonly thing on it. To the north is the

Chukchi Sea, and in every other direc-tion lies the Bering Land Bridge Na-tional Preserve, which probably ranksas one of the least visited national parksin the country. During the last ice age,the land bridge—exposed by a drop insea levels of more than three hundredfeet—grew to be nearly a thousand

miles wide. The preserve occupies thatpart of it which, after more than tenthousand years of warmth, still remainsabove water.

Shishmaref (pop. 591) is an Inupiatvillage, and it has been inhabited, at leaston a seasonal basis, for several centu-ries.As in many native villages in Alaska,

Iceland ’s Svínafellsjökull. Nearly every major glacier in the world is shrinking. Photograph by James Balog.

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life there combines—often disconcert-ingly—the very ancient and the totallymodern.Almost everyone in Shishmarefstill lives off subsistence hunting, pri-marily for bearded seals but also for wal-rus, moose, rabbit, and migrating birds.When I visited the village one day lastApril, the spring thaw was under way,and the seal-hunting season was about to begin. (Wandering around, I almosttripped over the remnants of the previ-ous year’s catch emerging from storageunder the snow.) At noon, the village’stransportation planner, Tony Weyiou-anna, invited me to his house for lunch.

In the living room, an enormous televi-sion set tuned to the local public-accessstation was playing a rock soundtrack.Messages like “Happy Birthday to thefollowing elders . . .”kept scrolling acrossthe screen.

Traditionally, the men in Shishmarefhunted for seals by driving out over thesea ice with dogsleds or,more recently,onsnowmobiles.After they hauled the sealsback to the village, the women wouldskin and cure them, a process that takesseveral weeks. In the early nineteen-nineties, the hunters began to notice thatthe sea ice was changing. (Although the

claim that the Eskimos have hundredsof words for snow is an exaggeration,the Inupiat make distinctions amongmany different types of ice, includingsikuliaq, “young ice,” sarri, “pack ice,”and tuvaq, “landlocked ice.”) The icewas starting to form later in the fall, andalso to break up earlier in the spring.Once, it had been possible to drive outtwenty miles; now, by the time the seals arrived, the ice was mushy half thatdistance from shore. Weyiouanna de-scribed it as having the consistency ofa “slush puppy.” When you encoun-ter it, he said, “your hair starts sticking

anese,” Kiyutelluk told me. “Well, theyhad some good scientists, and it’s be-come true.”

The National Academy of Sciencesundertook its first rigorous study of

global warming in 1979. At that point,climate modelling was still in its infancy,and only a few groups,one led by SyukuroManabe, at the National Oceanic andAtmospheric Administration, and an-other by James Hansen, at NASA’s God-dard Institute for Space Studies,had con-sidered in any detail the effects of addingcarbon dioxide to the atmosphere. Still,the results of their work were alarm-ing enough that President Jimmy Cartercalled on the academy to investigate. Anine-member panel was appointed, ledby the distinguished meteorologist JuleCharney, of M.I.T.

The Ad Hoc Study Group on Car-bon Dioxide and Climate, or the Char-ney panel, as it became known, met forfive days at the National Academy of Sci-ences’ summer study center, in WoodsHole,Massachusetts. Its conclusions wereunequivocal. Panel members had lookedfor flaws in the modellers’ work but hadbeen unable to find any. “If carbon diox-ide continues to increase, the study groupfinds no reason to doubt that climatechanges will result and no reason to be-lieve that these changes will be negli-gible,” the scientists wrote. For a dou-bling of CO2 from pre-industrial levels,they put the likely global temperature rise at between two and a half and eightdegrees Fahrenheit. The panel membersweren’t sure how long it would take forchanges already set in motion to becomemanifest,mainly because the climate sys-tem has a built-in time delay. It couldtake “several decades,” they noted. Forthis reason, what might seem like themost conservative approach—waiting forevidence of warming in order to assessthe models’accuracy—actually amountedto the riskiest possible strategy:“We maynot be given a warning until the CO2loading is such that an appreciable cli-mate change is inevitable.”

It is now twenty-five years since the Charney panel issued its report, and,in that period, Americans have beenalerted to the dangers of global warmingso many times that volumes have beenwritten just on the history of efforts todraw attention to the problem. (The Na-

tional Academy of Sciences alone has issued nearly two hundred reports onglobal warming; the most recent, “Ra-diative Forcing of Climate Change,”waspublished just last month.) During thissame period, worldwide carbon-dioxideemissions have continued to increase,from five billion billion metric tons ayear to seven billion, and the earth’s tem-perature,much as predicted by Manabe’sand Hansen’s models, has steadily risen.The year 1990 was the warmest year onrecord until 1991, which was equallyhot. Almost every subsequent year hasbeen warmer still. The year 1998 ranksas the hottest year since the instrumen-tal temperature record began, but it isclosely followed by 2002 and 2003,whichare tied for second; 2001, which is third;and 2004,which is fourth.Since climateis innately changeable, it’s difficult to say when, exactly, in this sequence natu-ral variation could be ruled out as thesole cause. The American GeophysicalUnion, one of the nation’s largest andmost respected scientific organizations,decided in 2003 that the matter hadbeen settled.At the group’s annual meet-ing that year, it issued a consensus state-ment declaring,“Natural influences can-not explain the rapid increase in globalnear-surface temperatures.” As best ascan be determined, the world is nowwarmer than it has been at any point inthe last two millennia, and, if currenttrends continue, by the end of the cen-tury it will likely be hotter than at anypoint in the last two million years.

In the same way that global warm-ing has gradually ceased to be merely atheory, so, too, its impacts are no longerjust hypothetical. Nearly every majorglacier in the world is shrinking; those inGlacier National Park are retreating soquickly it has been estimated that theywill vanish entirely by 2030. The oceansare becoming not just warmer but moreacidic; the difference between day andnighttime temperatures is diminishing;animals are shifting their ranges pole-ward; and plants are blooming days, andin some cases weeks, earlier than theyused to.These are the warning signs thatthe Charney panel cautioned againstwaiting for, and while in many parts of the globe they are still subtle enoughto be overlooked, in others they can nolonger be ignored. As it happens, themost dramatic changes are occurring in

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up. Your eyes are wide open. You can’teven blink.” It became too dangerous tohunt using snowmobiles, and the menswitched to boats.

Soon, the changes in the sea icebrought other problems. At its highestpoint, Shishmaref is only twenty-twofeet above sea level, and the houses,many built by the U.S. government, aresmall, boxy, and not particularly sturdy-looking. When the Chukchi Sea frozeearly, the layer of ice protected the vil-lage, the way a tarp prevents a swim-ming pool from getting roiled by thewind. When the sea started to freezelater,Shishmaref became more vulnera-ble to storm surges. A storm in Octo-ber, 1997, scoured away a hundred-and-twenty-five-foot-wide strip from thetown’s northern edge; several houseswere destroyed, and more than a dozenhad to be relocated. During anotherstorm, in October, 2001, the village wasthreatened by twelve-foot waves. In thesummer of 2002, residents of Shish-maref voted, a hundred and sixty-one totwenty, to move the entire village to themainland. Last year, the federal govern-ment completed a survey of possiblesites for a new village. Most of the spotsthat are being considered are in areasnearly as remote as Sarichef, with noroads or nearby cities, or even settle-ments. It is estimated that a full reloca-tion will cost at least a hundred andeighty million dollars.

People I spoke to in Shishmaref ex-pressed divided emotions about the pro-posed move.Some worried that,by leav-ing the tiny island, they would give uptheir connection to the sea and becomelost.“It makes me feel lonely,”one womansaid.Others seemed excited by the pros-pect of gaining certain conveniences, likerunning water, that Shishmaref lacks.Everyone seemed to agree, though, thatthe village’s situation, already dire, waslikely only to get worse.

Morris Kiyutelluk, who is sixty-five,has lived in Shishmaref almost all hislife. (His last name, he told me, means“without a wooden spoon.”) I spoke tohim while I was hanging around thebasement of the village church, whichalso serves as the unofficial headquar-ters for a group called the ShishmarefErosion and Relocation Coalition.“Thefirst time I heard about global warm-ing, I thought, I don’t believe those Jap-

those places, like Shishmaref, where the fewest people tend to live. This dis-proportionate effect of global warm-ing in the far north was also predicted byearly climate models, which forecast, incolumn after column of FORTRAN-gen-erated figures, what today can be meas-ured and observed directly: the Arctic ismelting.

Most of the land in the Arctic, andnearly a quarter of all the land in

the Northern Hemisphere—some fiveand a half billion acres—is underlaid byzones of permafrost.A few months afterI visited Shishmaref, I took a trip throughthe interior of Alaska with Vladimir Ro-manovsky,a geophysicist and permafrostexpert at the University of Alaska. I flewinto Fairbanks,where Romanovsky lives,and when I arrived the whole city wasenveloped in a dense haze that lookedlike fog but smelled like burning rubber.People kept telling me that I was lucky I hadn’t come a couple of weeks earlier,when it had been much worse.“Even thedogs were wearing masks,”one woman Imet said. I must have smiled. “I am notjoking,” she told me.

Fairbanks, Alaska’s second-largestcity, is surrounded on all sides by forest,and virtually every summer lightning setsoff fires in these forests, which fill the airwith smoke for a few days or, in bad years,weeks.This past summer, the fires startedearly, in June, and were still burning twoand a half months later; by the time ofmy visit, in late August, a record 6.3 mil-lion acres—an area roughly the size ofNew Hampshire—had been incinerated.The severity of the fires was clearly linkedto the weather, which had been excep-tionally hot and dry; the average sum-mertime temperature in Fairbanks wasthe highest on record, and the amount ofrainfall was the third lowest.

On my second day in Fairbanks, Ro-manovsky picked me up at my hotel foran underground tour of the city. Likemost permafrost experts,he is from Rus-sia. (The Soviets more or less inventedthe study of permafrost when they de-cided to build their gulags in Siberia.) Abroad man with shaggy brown hair anda square jaw, Romanovsky as a studenthad had to choose between playing pro-fessional hockey and becoming a geo-physicist. He had opted for the latter, hetold me, because “I was little bit better

scientist than hockey player.” He wenton to earn two master’s degrees and twoPh.D.s. Romanovsky came to get me at 10 A.M.; owing to all the smoke, itlooked like dawn.

Any piece of ground that has re-mained frozen for at least two years is, bydefinition, permafrost. In some places,like eastern Siberia, permafrost runsnearly a mile deep; in Alaska, it variesfrom a couple of hundred feet to a cou-ple of thousand feet deep. Fairbanks,which is just below the Arctic Circle, issituated in a region of discontinuous per-mafrost, meaning that the city is freckledwith regions of frozen ground. One ofthe first stops on Romanovsky’s tour wasa hole that had opened up in a patch of permafrost not far from his house. Itwas about six feet wide and five feet deep. Nearby were the outlines of other,even bigger holes, which, Romanovskytold me, had been filled with gravel by the local public-works department. Theholes, known as thermokarsts, had ap-peared suddenly when the permafrost

gave way, like a rotting floorboard. (Thetechnical term for thawed permafrost istalik, from a Russian word meaning “notfrozen.”) Across the road, Romanovskypointed out a long trench running intothe woods.The trench,he explained,hadbeen formed when a wedge of under-ground ice had melted. The spruce treesthat had been growing next to it, or per-haps on top of it, were now listing at oddangles, as if in a gale. Locally, such treesare called “drunken.”A few of the spruceshad fallen over. “These are very drunk,”Romanovsky said.

In Alaska, the ground is riddled withice wedges that were created during the last glaciation, when the cold earthcracked and the cracks filled with water.The wedges, which can be dozens oreven hundreds of feet deep, tended toform in networks, so that when they meltthey leave behind connecting diamond-or hexagonal-shaped depressions. A fewblocks beyond the drunken forest, wecame to a house where the front yardshowed clear signs of ice-wedge melt-

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off. The owner, trying to make the best of things, had turned the yard into aminiature-golf course. Around the cor-ner, Romanovsky pointed out a house—no longer occupied—that had basicallysplit in two; the main part was leaning tothe right and the garage toward the left.The house had been built in the sixties orearly seventies; it had survived until al-most a decade ago, when the permafrostunder it started to degrade.Romanovsky’smother-in-law used to own two houseson the same block. He had urged her tosell them both.He pointed out one,nowunder new ownership; its roof had devel-oped an ominous-looking ripple. (WhenRomanovsky went to buy his own house,he looked only in permafrost-free areas.)

“Ten years ago, nobody cared aboutpermafrost,”he told me.“Now everybodywants to know.” Measurements that Ro-manovsky and his colleagues at the Uni-versity of Alaska have made around Fair-banks show that the temperature of thepermafrost has risen to the point where,in many places, it is now less than one degree below freezing. In places wherepermafrost has been disturbed, by roadsor houses or lawns, much of it is al-ready thawing. Romanovsky has alsobeen monitoring the permafrost on theNorth Slope and has found that there,too, are regions where the permafrost is

very nearly thirty-two degrees Fahren-heit.While the age of permafrost is diffi-cult to determine,Romanovsky estimatesthat most of it in Alaska probably datesback to the beginning of the last glacialcycle.This means that if it thaws it will bedoing so for the first time in more than ahundred and twenty thousand years.“It’sreally a very interesting time,” he said.

The next morning,Romanovsky pickedme up at seven. We were going to

drive from Fairbanks nearly five hun-dred miles north to the town of Dead-horse, on Prudhoe Bay, to collect datafrom electronic monitoring stations thatRomanovsky had set up. Since the roadwas largely unpaved, he had rented atruck for the occasion. Its windshieldwas cracked in several places. When Isuggested this could be a problem, Ro-manovsky assured me that it was “typicalAlaska.” For provisions, he had broughtalong an oversized bag of Tostitos.

The road that we were travelling onhad been built for Alaskan oil, and thepipeline followed it, sometimes to theleft, sometimes to the right. (Because ofthe permafrost, the pipeline runs mostlyaboveground, on pilings.) Trucks keptpassing us, some with severed caribouheads strapped to their roofs, others ad-vertising the Alyeska Pipeline Service

Company.About two hours outside Fair-banks, we started to pass through tractsof forest that had recently burned, thentracts that were still smoldering, and, fi-nally, tracts that were still, intermittently,in flames.The scene was part Dante,part“Apocalypse Now.” We crawled alongthrough the smoke. Beyond the town ofColdfoot—really just a gas station—wepassed the tree line. An evergreen wasmarked with a plaque that read “Far-thest North Spruce Tree on the AlaskaPipeline: Do Not Cut.” Predictably,someone had taken a knife to it. A deepgouge around the trunk was bound withduct tape.“I think it will die,”Romanov-sky said.

Finally,at around five in the afternoon,we reached the turnoff for the first moni-toring station. Because one of Roman-ovsky’s colleagues had nursed dreams—never realized—of travelling to it byplane, it was near a small airstrip, on thefar side of a river. We pulled on rubberboots and forded the river, which, owingto the lack of rain, was running low. Thesite consisted of a few posts sunk into thetundra; a solar panel; a two-hundred-foot-deep borehole with heavy-gaugewire sticking out of it; and a white con-tainer, resembling an ice chest, that heldcomputer equipment. The solar panel,which the previous summer had beenmounted a few feet off the ground, wasnow resting on the scrub. At first, Ro-manovsky speculated that this was a resultof vandalism, but after inspecting thingsmore closely he decided that it was thework of a bear. While he hooked up alaptop computer to one of the monitorsinside the white container, my job was tokeep an eye out for wildlife.

For the same reason that it is sweatyin a coal mine—heat flux from the centerof the earth—permafrost gets warmerthe farther down you go. Under equilib-rium conditions—which is to say, whenthe climate is stable—the very warmesttemperatures in a borehole will be foundat the bottom and they will decreasesteadily as you go higher. In these cir-cumstances, the lowest temperature willbe found at the permafrost’s surface, sothat, plotted on a graph, the results willbe a tilted line. In recent decades, though,the temperature profile of Alaska’s per-mafrost has drooped. Now, instead ofa straight line, what you get is shapedmore like a sickle. The permafrost is

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still warmest at the very bottom, but instead of being coldest at the top it iscoldest somewhere in the middle, andwarmer again toward the surface.This isan unambiguous sign that the climate isheating up.

“It’s very difficult to look at trends inair temperature, because it’s so variable,”Romanovsky explained after we wereback in the truck,bouncing along towardDeadhorse. It turned out that he hadbrought the Tostitos to stave off not hun-ger but fatigue—the crunching, he said,kept him awake—and by now the bagwas more than half empty. “So one yearyou have around Fairbanks a mean an-nual temperature of zero”—thirty-twodegrees Fahrenheit—“and you say, ‘Ohyeah, it’s warming,’ and other years youhave a mean annual temperature ofminus six”—twenty-one degrees Fahr-enheit—“and everybody says, ‘Where?Where is your global warming?’ In the airtemperature, the signal is very small com-pared to noise.What permafrost does is itworks as a low-pass filter. That’s why wecan see trends much easier in permafrosttemperatures than we can see them in at-mosphere.” In most parts of Alaska, thepermafrost has warmed by three degreessince the early nineteen-eighties. In someparts of the state, it has warmed by nearlysix degrees.

When you walk around in the Arc-tic, you are stepping not on per-

mafrost but on something called the “ac-tive layer.” The active layer, which can be anywhere from a few inches to a fewfeet deep, freezes in the winter but thawsover the summer, and it is what supportsthe growth of plants—large spruce treesin places where conditions are favorableenough and, where they aren’t, shrubsand, finally, just lichen. Life in the ac-tive layer proceeds much as it does inmore temperate regions,with one criticaldifference.Temperatures are so low thatwhen trees and grasses die they do notfully decompose.New plants grow out ofthe half-rotted old ones, and when theseplants die the same thing happens allover again.Eventually, through a processknown as cryoturbation, organic matteris pushed down beneath the active layerinto the permafrost, where it can sit forthousands of years in a botanical versionof suspended animation. (In Fairbanks,grass that is still green has been found in

permafrost dating back to the middle ofthe last ice age.) In this way, much like apeat bog or, for that matter, a coal de-posit, permafrost acts as a storage unitfor accumulated carbon.

One of the risks of rising tempera-tures is that this storage process can startto run in reverse. Under the right con-ditions, organic material that has beenfrozen for millennia will break down,giv-ing off carbon dioxide or methane,whichis an even more powerful greenhouse gas.In parts of the Arctic, this is already hap-pening. Researchers in Sweden, for ex-ample,have been measuring the methaneoutput of a bog known as the Stordalenmire,near the town of Abisko, for almostthirty-five years.As the permafrost in thearea has warmed, methane releases haveincreased, in some spots by up to sixty percent. Thawing permafrost could makethe active layer more hospitable to plants,which are a sink for carbon. Even this,though, probably wouldn’t offset the re-lease of greenhouse gases. No one knowsexactly how much carbon is stored in theworld’s permafrost, but estimates run ashigh as four hundred and fifty billionmetric tons.

“It’s like ready-use mix—just a lit-tle heat, and it will start cooking,” Ro-manovsky told me. It was the day afterwe had arrived in Deadhorse, and wewere driving through a steady drizzle outto another monitoring site. “I think it’sjust a time bomb, just waiting for a littlewarmer conditions.” Romanovsky waswearing a rain suit over his canvas workclothes. I put on a rain suit that he hadbrought along for me. He pulled a tarpout of the back of the truck.

Whenever he has had funding, Ro-manovsky has added new monitoringsites to his network. There are now sixtyof them,and while we were on the NorthSlope he spent all day and also part ofthe night—it stayed light until nearlyeleven—rushing from one to the next.At each site, the routine was more or lessthe same.First,Romanovsky would hook

up his computer to the data logger,whichhad been recording permafrost tempera-tures on an hourly basis since the previ-ous summer. (When it was raining, hewould perform this step hunched underthe tarp.) Then he would take out a metalprobe shaped like a “T” and poke it intothe ground at regular intervals,measuringthe depth of the active layer. The probewas a metre long, which, it turned out,was no longer quite long enough. Thesummer had been so warm that almosteverywhere the active layer had growndeeper, in some spots by just a few cen-timetres, in other spots by more than that;in places where the active layer was par-ticularly deep, Romanovsky had had towork out a new way of measuring it usingthe probe and a wooden ruler.Eventually,he explained, the heat that had gone intoincreasing the depth of the active layerwould work its way downward, bringingthe permafrost that much closer to thethawing point.“Come back next year,”headvised me.

On the last day I spent on the NorthSlope,a friend of Romanovsky’s,NicolaiPanikov, a microbiologist at the Stev-ens Institute of Technology, in New Jer-sey, arrived. Panikov had come to collectcold-loving microörganisms known aspsychrophiles.He was planning to studythese organisms in order to determinewhether they could have functioned inthe sort of conditions that, it is believed,were once found on Mars. Panikov toldme that he was quite convinced that Mar-tian life existed—or, at least,had existed.Romanovsky expressed his opinion onthis by rolling his eyes; nevertheless, hehad agreed to help Panikov dig up somepermafrost.

That day, I also flew with Romanov-sky by helicopter to a small island in theArctic Ocean, where he had set up yet another monitoring site. The island, justnorth of the seventieth parallel, was ableak expanse of mud dotted with littleclumps of yellowing vegetation. It wasfilled with ice wedges that were starting tomelt, creating a network of polygonal de-pressions.The weather was cold and wet,so while Romanovsky hunched under histarp I stayed in the helicopter and chattedwith the pilot. He had lived in Alaskasince 1967.“It’s definitely gotten warmersince I’ve been here,” he told me. “I havereally noticed that.”

When Romanovsky emerged,we took

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a walk around the island. Apparently,in the spring it had been a nesting site for birds, because everywhere we went there were bits of eggshell and piles ofdroppings.The island was only about tenfeet above sea level, and at the edges itdropped off sharply into the water. Ro-manovsky pointed out a spot along theshore where the previous summer a seriesof ice wedges had been exposed. Theyhad since melted, and the ground behindthem had given way in a cascade of blackmud. In a few years, he said, he expectedmore ice wedges would be exposed, andthen these would melt, causing furthererosion. Although the process was dif-ferent in its mechanics from what wasgoing on in Shishmaref, it had much thesame cause and, according to Romanov-sky, was likely to have the same result.“Another disappearing island,” he said,gesturing toward some freshly exposedbluffs. “It’s moving very, very fast.”

On September 18, 1997, the DesGroseilliers, a three-hundred-and-

eighteen-foot-long icebreaker with abright-red hull, set out from the town ofTuktoyaktuk, on the Beaufort Sea, andheaded north under overcast skies. Nor-mally, the Des Groseilliers,which is basedin Québec City, is used by the CanadianCoast Guard, but for this particular jour-ney it was carrying a group of Americangeophysicists,who were planning to jam itinto an ice floe.The scientists were hopingto conduct a series of experiments as theyand the ship and the ice floe all drifted,as one, around the Arctic Ocean.The ex-pedition had taken several years to pre-pare for, and during the planning phase its organizers had carefully consulted thefindings of a previous Arctic expedition,which took place back in 1975. Based onthose findings, they had decided to lookfor a floe averaging nine feet thick. Butwhen they reached the area where theyplanned to overwinter—at seventy-fivedegrees north latitude—they found thatnot only were there no floes nine feet thickbut there were barely any that reached sixfeet. One of the scientists on board re-called the reaction on the Des Groseilliersthis way: “It was like ‘Here we are, alldressed up and nowhere to go.’We imag-ined calling the sponsors at the NationalScience Foundation and saying, ‘Well,youknow, we can’t find any ice.’ ”

Sea ice in the Arctic comes in two va-

rieties.There is seasonal ice,which formsin the winter and then melts in the sum-mer, and perennial ice, which persistsyear-round.To the untrained eye, all seaice looks pretty much the same, but bylicking it you can get a good idea of howlong a particular piece has been floatingaround.When ice begins to form in sea-water, it forces out the salt, which has noplace in the crystal structure. As the icegets thicker, the rejected salt collects intiny pockets of brine too highly concen-trated to freeze. If you suck on a piece of first-year ice, it will taste salty. Even-tually, if the ice survives, these pockets of brine drain out through fine, vein-likechannels, and the ice becomes fresher.Multiyear ice is so fresh that if you meltit you can drink it.

The most precise measurements ofArctic sea ice have been made by NASA,using satellites equipped with microwavesensors. In 1979, the satellite data show,perennial sea ice covered 1.7 billion acres,or an area nearly the size of the continen-tal United States. The ice’s extent variesfrom year to year,but since then the over-all trend has been strongly downward.The losses have been particularly great inthe Beaufort and Chukchi Seas, and alsoconsiderable in the Siberian and LaptevSeas. During this same period, an atmo-spheric circulation pattern known as theArctic Oscillation has mostly been in whatclimatologists call a “positive”mode.Thepositive Arctic Oscillation is marked bylow pressure over the Arctic Ocean,and ittends to produce strong winds and highertemperatures in the far north.No one re-ally knows whether the recent behav-ior of the Arctic Oscillation is indepen-dent of global warming or a product ofit. By now, though, the perennial sea icehas shrunk by roughly two hundred andfifty million acres, an area the size of NewYork, Georgia, and Texas combined. Ac-cording to mathematical models, eventhe extended period of a positive ArcticOscillation can account for only part ofthis loss.

The researchers aboard the Des Gro-seilliers knew that the Arctic sea ice wasretreating; that was, in fact, why they were there. At the time, however, therewasn’t much data on trends in sea-icedepth. (Since then, a limited amount ofinformation on this topic—gathered, forrather different purposes,by nuclear sub-marines—has been declassified.) Eventu-

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NEW LIFE In a deal reached last week, the Oak

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Bar at the Plaza, which had been scheduled to close, will reopen after the hotel is renovated. Photograph by Robert Polidori.

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ally, the researchers decided to settle forthe best ice floe they could find. Theypicked one that stretched over some thirtysquare miles and in some spots was sixfeet thick, in some spots three.Tents wereset up on the floe to house experiments,and a safety protocol was established:anyone venturing out onto the ice had totravel with a buddy and a radio. (Manyalso carried a gun, in case of polar-bearproblems.) Some of the scientists specu-lated that, since the ice was abnormallythin, it would grow during the expedi-tion. The opposite turned out to be thecase. The Des Groseilliers spent twelvemonths frozen into the floe, and, duringthat time, it drifted some three hundredmiles north. Nevertheless, at the end ofthe year, the average thickness of the icehad declined, in some spots by as much asa third. By August, 1998, so many of thescientists had fallen through that a newrequirement was added to the protocol:anyone who set foot off the ship had towear a life jacket.

Donald Perovich has studied sea icefor thirty years, and on a rainy day

last fall I went to visit him at his office in Hanover, New Hampshire. Perovichworks for the Cold Regions Researchand Engineering Laboratory, or CRREL

(pronounced “crell”), a division of theU.S. Army established in 1961 in antic-ipation of a very cold war. (The assump-tion was that if the Soviets invaded theywould probably do so from the north.)He is a tall man with black hair, veryblack eyebrows, and an earnest manner.His office is decorated with photographsfrom the Des Groseilliers expedition, forwhich he served as the lead scientist;there are shots of the ship, the tents, and,if you look closely enough, the bears.One grainy-looking photo shows some-one dressed up as Santa Claus, celebrat-ing Christmas out on the ice.“The mostfun you could ever have” was how Pe-rovich described the expedition to me.

Perovich’s particular area of expertise,in the words of his CRREL biography, is“the interaction of solar radiation with seaice.”During the Des Groseilliers expedi-tion, he spent most of his time monitor-ing conditions on the floe using a deviceknown as a spectroradiometer.Facing to-ward the sun, a spectroradiometer mea-sures incident light, and facing towardearth it measures reflected light. If you di-

vide the latter by the former, you get aquantity known as albedo. (The termcomes from the Latin word for “white-ness.”) During April and May,when con-ditions on the floe were relatively stable,Perovich took measurements with hisspectroradiometer once a week, and dur-ing June,July,and August,when they werechanging more rapidly,he took measure-ments every other day. The arrangementallowed him to plot exactly how thealbedo varied as the snow on top of the ice turned to slush, and then the slush be-came puddles, and, finally, some of thepuddles melted through to the waterbelow.

An ideal white surface, which re-flected all the light that shone on it,would have an albedo of one, and anideal black surface, which absorbed allthe light, would have an albedo of zero.The albedo of the earth, in aggregate,is 0.3, meaning that a little less than athird of the sunlight that hits it gets re-flected back out. Anything that changesthe earth’s albedo changes how muchenergy the planet absorbs, with poten-tially dramatic consequences. “I like itbecause it deals with simple concepts,but it’s important,” Perovich told me.

At one point, Perovich asked me toimagine that we were looking down atthe earth from a spaceship above theNorth Pole. “It’s springtime, and the iceis covered with snow, and it ’s reallybright and white,” he said. “It reflectsover eighty per cent of the incident sunlight. The albedo’s around 0.8, 0.9.Now, let’s suppose that we melt that iceaway and we’re left with the ocean. Thealbedo of the ocean is less than 0.1; it’slike 0.07.

“Not only is the albedo of the snow-covered ice high; it’s the highest of any-thing we find on earth,” he went on.“And not only is the albedo of waterlow; it’s pretty much as low as anythingyou can find on earth. So what you’redoing is you’re replacing the best re-flector with the worst reflector.” Themore open water that’s exposed, themore solar energy goes into heating theocean. The result is a positive feedback,similar to the one between thawing per-mafrost and carbon releases, only moredirect. This so-called ice-albedo feed-back is believed to be a major reasonthat the Arctic is warming so rapidly.

“As we melt that ice back, we can put

more heat into the system, which meanswe can melt the ice back even more,which means we can put more heat intoit, and, you see, it just kind of builds onitself,” Perovich said. “It takes a smallnudge to the climate system and ampli-fies it into a big change.”

Afew dozen miles to the east ofCRREL, not far from the Maine-

New Hampshire border, is a small parkcalled the Madison Boulder NaturalArea. The park’s major—indeed, only—attraction is a block of granite the size ofa two-story house.The Madison Boulderis thirty-seven feet wide and eighty-threefeet long and weighs about ten millionpounds. It was plucked out of the WhiteMountains and deposited in its currentlocation eleven thousand years ago,and itillustrates how relatively minor changesto the climate system have, when ampli-fied, yielded cataclysmic results.

Geologically speaking, we are nowliving in a warm period after an ice age.Over the past two million years,huge icesheets have advanced across the North-ern Hemisphere and retreated againmore than twenty times. (Each majorglaciation tended, for obvious reasons,to destroy the evidence of its predeces-sors.) The most recent advance, calledthe Wisconsin, began roughly a hun-dred and twenty thousand years ago,when ice began to creep outward fromcenters in Scandinavia, Siberia, and thehighlands near Hudson Bay.By the timethe sheets had reached their maximumsouthern extent, most of New Englandand New York and a good part of theupper Midwest were buried under icenearly a mile thick. The ice sheets wereso heavy that they depressed the crust ofthe earth,pushing it down into the man-tle. (In some places, the process of re-covery, known as isostatic rebound, isstill going on.) As the ice retreated, it de-posited, among other landmarks, the ter-minal moraine called Long Island.

It is now known, or at least almostuniversally accepted, that glacial cyclesare initiated by slight,periodic variationsin the earth’s orbit. These orbital varia-tions alter the distribution of sunlight atdifferent latitudes during different sea-sons according to a complex pattern thattakes a hundred thousand years to com-plete. But orbital variations in them-selves aren’t nearly sufficient to produce

That’s what we’re doing as a society.This climate, if it starts rolling, we don’treally know where it will stop.”

As a cause for alarm, global warm-ing could be said to be a nineteen-

seventies idea; as pure science, however,it is much older than that. In 1859, aBritish physicist named John Tyndall,experimenting with a machine he hadbuilt—the world’s first ratio spectro-photometer—set out to study the heat-trapping properties of various gases.Tyndall found that the most commonelements in the air—oxygen and nitro-gen—were transparent to both visibleand infrared radiation.Gases like carbondioxide, methane, and water vapor, bycontrast, were not. Tyndall was quick to appreciate the implications of his discovery: the imperfectly transparentgases,he declared,were largely responsi-ble for determining the earth’s climate.He likened their impact to that of a dam built across a river: just as a dam“causes a local deepening of the stream,so our atmosphere, thrown as a barrieracross the terrestrial rays,produces a local

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the sort of massive ice sheet that movedthe Madison Boulder.

The crushing size of that ice sheet,the Laurentide, which stretched oversome five million square miles, was theresult of feedbacks, more or less analo-gous to those now being studied in theArctic, only operating in reverse. As icebuilt up, albedo increased, leading to lessheat absorption and the growth of yetmore ice. At the same time, for reasonsthat are not entirely understood, as theice sheets advanced CO2 levels declined:during each of the most recent glacia-tions, carbon-dioxide levels dropped al-most precisely in synch with falling tem-peratures. During each warm period,when the ice retreated, CO2 levels roseagain. Ice cores from Antarctica con-tain a record of the atmosphere stretch-ing back more than four glacial cycles—minute samples of air get trapped intiny bubbles—and researchers who havestudied these cores have concluded thatfully half the temperature difference be-tween cold periods and warm ones canbe attributed to changes in the concen-trations of greenhouse gases. Antarcticice cores also show that carbon-dioxidelevels today are significantly higher thanthey have been at any other point in the last four hundred and twenty thou-sand years.

While I was at CRREL, Perovich tookme to meet a colleague of his named JohnWeatherly. Posted on Weatherly’s officedoor was a bumper sticker designed to bepasted—illicitly—on S.U.V.s. It said,“I’mChanging the Climate! Ask Me How!”For the last several years, Weatherly andPerovich have been working to translatethe data gathered on the Des Groseilliersexpedition into computer algorithms tobe used in climate forecasting.Weatherlytold me that some climate models—worldwide, there are about fifteen majorones in operation—predict that the pe-rennial sea-ice cover in the Arctic willdisappear entirely by the year 2080. Atthat point, although there would con-tinue to be seasonal ice that forms in win-ter, in summer the Arctic Ocean would be completely ice-free.“That’s not in ourlifetime,” he observed. “But it is in thelifetime of our kids.”

Later, back in his office, Perovich andI talked about the long-term prospects forthe Arctic.Perovich noted that the earth’sclimate system is so vast that it is not eas-

ily altered. “On the one hand, you think,It’s the earth’s climate system, it’s big; it’srobust. And, indeed, it has to be some-what robust or else it would be chang-ing all the time.” On the other hand, the climate record shows that it would be amistake to assume that change, when itcomes,will come slowly.Perovich offereda comparison that he had heard from aglaciologist friend.The friend likened theclimate system to a rowboat:“You can tipand then you’ll just go back.You can tip itand just go back. And then you tip it andyou get to the other stable state, which isupside down.”

Perovich said that he also liked a regional analogy. “The way I’ve beenthinking about it, riding my bike aroundhere, is, You ride by all these pasturesand they’ve got these big granite boul-ders in the middle of them. You’ve got abig boulder sitting there on this rollinghill. You can’t just go by this boulder.You’ve got to try to push it. So you startrocking it, and you get a bunch offriends, and they start rocking it, and fi-nally it starts moving. And then you re-alize, Maybe this wasn’t the best idea.

“Pardon me, but I couldn’t help overhearing your conversation.”

heightening of the temperature at theearth’s surface.”

The phenomenon that Tyndall iden-tified is now referred to as the “naturalgreenhouse effect.” It is not remotelycontroversial; indeed, it’s an essentialcondition of life on earth as we know it.To understand how it works, it helps toimagine the planet without it. In thatsituation, the earth would constantly bereceiving energy from the sun and, atthe same time, constantly radiating en-ergy back out to space.All hot bodies ra-diate, and the amount that they radiate isa function of their temperature. In orderfor the earth to be in equilibrium, thequantity of energy it sends into spacemust equal the quantity it is receiving.When, for whatever reason, equilibriumis disturbed, the planet will either warmup or cool down until the temperature isonce again sufficient to make the twoenergy streams balance out.

If there were no greenhouse gases,energy radiating from the surface of theearth would flow away from it unim-peded. In that case, it would be compar-atively easy to calculate how warm theplanet would have to get to throw backinto space the same amount of energy it absorbs from the sun. (This amountvaries widely by location and time ofyear; averaged out, it comes to some twohundred and thirty-five watts per squaremetre, or roughly the energy of fourhousehold light bulbs.) The result of thiscalculation is a frigid zero degrees.To use

Tyndall’s Victorian language, if the heat-trapping gases were removed from theair for a single night “the warmth of ourfields and gardens would pour itself un-requited into space, and the sun wouldrise upon an island held fast in the irongrip of frost.”

Greenhouse gases alter the situationbecause of their peculiar absorptive prop-erties. The sun’s radiation arrives mostlyin the form of visible light,which green-house gases allow to pass freely. Theearth’s radiation, meanwhile, is emittedmostly in the infrared part of the spec-trum. Greenhouse gases absorb infraredradiation and then reëmit it—some outtoward space and some back towardearth. This process of absorption andreëmission has the effect of limiting theoutward flow of energy; as a result, theearth’s surface and lower atmospherehave to be that much warmer before theplanet can radiate out the necessary twohundred and thirty-five watts per squaremetre.The presence of greenhouse gasesis what largely accounts for the fact thatthe average global temperature, insteadof zero, is actually a far more comfort-able fifty-seven degrees.

By the end of the nineteenth century,Tyndall’s work on the natural green-house effect had been extended to whatwould today be called the “enhancedgreenhouse effect.” In 1894, the Swedishchemist Svante Arrhenius became con-vinced that humans were altering theearth’s energy balance. Much as Tyndall

had tried to imagine what the worldwould be like in the absence of green-house gases, Arrhenius tried to imaginewhat it would be like in the presence ofmore of them. Starting on ChristmasEve, he set out to calculate what wouldhappen to the earth’s temperature if CO2levels were doubled.Arrhenius describedthe calculations as some of the most te-dious of his life. He routinely worked on them for fourteen hours a day, andwas not finished for nearly a year. Fi-nally, in December, 1895, he announcedhis results to the Royal Swedish Acad-emy of Sciences.

Like the natural greenhouse effect,the enhanced greenhouse effect is—intheoretical terms, at least—uncontrover-sial. If greenhouse-gas levels in the at-mosphere increase, all other things beingequal, the earth’s temperature will rise.The key uncertainties concern how thisprocess will play out in practice, since inthe real world all things rarely are equal.For several decades after Arrhenius com-pleted his calculations, scientists wereunsure to what extent mankind was evencapable of affecting atmospheric carbon-dioxide levels; the general assumptionwas that the oceans would absorb justabout everything humans could emit.Arrhenius himself predicted that itwould take three thousand years of coalburning to double the CO2 in the air, aprediction, it is now known, that was offby roughly twenty-eight centuries.

Swiss Camp is a research station set up in 1990 on a platform drilled into

the Greenland ice sheet. Because the icesheet is moving—ice flows like water,only more slowly—the camp is always inmotion: in fifteen years, it has migrated bymore than a mile, generally in a westerlydirection.Every summer, the whole placegets flooded,and every winter its contentssolidify.The cumulative effect of all this isthat almost nothing at Swiss Camp func-tions anymore the way it was supposed to.To get into it, you have to clamber up asnowdrift and descend through a trap-door in the roof, as if entering a ship’shold or a space module. The living quar-ters are no longer habitable, so now thescientists at the camp sleep outside, intents. (The one assigned to me was thesame sort used by Robert Scott on his ill-fated expedition to the South Pole.) Bythe time I arrived at the camp, late last

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66 THE NEW YORKER, APRIL 25, 2005

“I’m sorry, Eddie, but the old man wants me to kill you.”

• •

May, someone had jackhammered outthe center of the workspace but had leftthe desks encased in three-foot-highblocks of ice. Inside them I could dimlymake out a tangle of wires,a bulging plas-tic bag, and an old dustpan.

Konrad Steffen, a professor of ge-ography at the University of Colorado,is the director of Swiss Camp. A na-tive of Zurich, Steffen is tall and lanky,with pale-blue eyes, blondish hair, and a blondish-gray beard. He fell in lovewith the Arctic when, as a graduate stu-dent in 1975,he spent a summer on AxelHeiberg Island, four hundred milesnorthwest of the north magnetic pole.A few years later, for his doctoral disser-tation,he lived for two winters on the seaice off Baffin Island. (Steffen told methat for his honeymoon he had wantedto take his wife to Spitsbergen, an islandfive hundred miles north of Norway,butshe demurred, and they had ended updriving across the Sahara instead.)

When Steffen planned Swiss Camp—he built much of the place himself—itwas not with global warming in mind.Rather, he was interested in meteorolog-ical conditions on what is known as theice sheet’s “equilibrium line.” Along thisline, winter snow and summer melt aresupposed to be precisely in balance. But,in recent years, “equilibrium” has becomean increasingly elusive quality. In thesummer of 2002, the ice sheet melted to an unprecedented extent. Satellite im-ages taken by NASA showed that snowhad melted up to an elevation of sixty-five hundred feet. In some of these spots,ice-core records revealed, liquid water had not been seen for hundreds, perhapsthousands, of years. The following win-ter, there was an unusually low snowfall,and in the summer of 2003 the melt wasso great that, around Swiss Camp, fivefeet of ice were lost.

When I arrived at the camp, the 2004melt season was already under way.This,to Steffen, was a matter of both intensescientific interest and serious practicalconcern. A few days earlier, one of hisgraduate students, Russell Huff, and apostdoc, Nicolas Cullen, had driven outon snowmobiles to service some weatherstations closer to the coast. The snowthere was melting so fast that they hadhad to work until five in the morning,andthen take a long detour back, to avoidgetting caught in the quickly forming

rivers. Steffen wanted to get everythingthat needed to be done completed aheadof schedule, in case everyone had to packup and leave early. My first day at SwissCamp he spent fixing an antenna thathad fallen over in the previous year’s melt.It was bristling with equipment, like ahigh-tech Christmas tree. Even on a rel-atively warm day on the ice sheet, whichthis was, it never gets more than a few de-grees above freezing, and I was walkingaround in a huge parka, two pairs of pantsplus long underwear, and two pairs ofgloves. Steffen, meanwhile, was tinker-ing with the antenna with his bare hands.He has spent fourteen summers at SwissCamp, and I asked him what he hadlearned during that time. He answeredwith another question.

“Are we disintegrating part of theGreenland ice sheet over the longerterm?” he asked. He was sorting througha tangle of wires that to me all lookedthe same but must have had some sort of distinguishing characteristics.“Whatthe regional models tell us is that we will get more melt at the coast. It willcontinue to melt. But warmer air canhold more water vapor, and at the top ofthe ice sheet you’ll get more precipita-tion. So we’ll add more snow there.We’ll get an imbalance of having moreaccumulation at the top, and more meltat the bottom. The key question now is:What is the dominant one, the moremelt or the increase?”

Greenland’s ice sheet is the second-largest on earth. (Antarctica’s is the

largest.) In its present form, the Green-land ice sheet is, quite literally, a relic ofthe last glaciation.The top layers consistof snow that fell recently. Beneath theselayers is snow that fell centuries and thenmillennia ago, until, at the very bottom,there is snow that fell a hundred andthirty thousand years ago. Under cur-rent climate conditions, the ice sheetprobably would not form, and it is onlyits enormous size that has sustained it forthis long. In the middle of the island, theice is so thick—nearly two miles—that itcreates a kind of perpetual winter. Snowfalls in central Greenland year-roundand it never melts, although, over time,the snow gets compacted into ice and ispressed out toward the coast. There,eventually, it either calves off into ice-bergs or flows away. In summertime,

lakes of a spectacular iridescent blueform at the ice sheet’s lower elevations;these empty into vast rivers that fan out toward the sea.Near Swiss Camp—elevation 3,770 feet—there is a huge de-pression where one such lake forms eachJuly, but by that point no one is aroundto see it: it would be far too dangerous.

Much of what is known about theearth’s climate over the last hundred thou-sand years comes from ice cores drilled in central Greenland, along a line knownas the ice divide. Owing to differences between summer and winter snow, eachlayer in a Greenland core can be indi-vidually dated, much like the rings ofa tree. Then, by analyzing the isotopiccomposition of the ice, it is possible to de-termine how cold it was at the time eachlayer was formed. (Although ice coresfrom Antarctica contain a much longerclimate record, it is not as detailed.) Overthe last decade, three Greenland coreshave been drilled to a depth of ten thou-sand feet, and these cores have prompteda rethinking of how the climate operates.Where once the system was thought tochange, as it were, only glacially, now it isknown to be capable of sudden and un-predictable reversals. One such reversal,called the Younger Dryas, after a smallArctic plant—Dryas octopetala—that sud-denly reappeared in Scandinavia, tookplace roughly twelve thousand eight hun-dred years ago. At that point, the earth,which had been warming rapidly, wasplunged back into glacial conditions. Itremained frigid for twelve centuries andthen warmed again, even more abruptly.In Greenland, average annual tempera-tures shot up by nearly twenty degrees ina single decade.

As a continuous temperature record,the Greenland ice cores stop provid-ing reliable information right around the start of the last glacial cycle. Cli-mate records pieced together from othersources indicate that the last interglacial,which is known as the Eemian, wassomewhat warmer than the present one,the Holocene. They also show that sealevels during that time were at least fif-teen feet higher than they are today.Onetheory attributes this to a collapse ofthe West Antarctic Ice Sheet. A secondholds that meltwater from Greenlandwas responsible. (When sea ice melts, itdoes not affect sea level, because the ice, which was floating, was already dis-

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THE NEW YORKER, APRIL 25, 2005 67

placing an equivalent volume of water.)All told, the Greenland ice sheet holdsenough water to raise sea levels world-wide by twenty-three feet. Scientists atNASA have calculated that throughoutthe nineteen-nineties the ice sheet, de-spite some thickening at the center, wasshrinking by twelve cubic miles per year.

Jay Zwally is a NASA scientist whoworks on a satellite project known

as ICESat. He is also a friend of Steffen’s,and about ten years ago he got the idea of installing global-positioning-systemreceivers around Swiss Camp to studychanges in the ice sheet ’s elevation.Zwally happened to be at the campwhile I was there, and the second day ofmy visit we all got onto snowmobilesand headed out to a location known asJAR 1 (for Jakobshavn Ablation Region)to reinstall a G.P.S. receiver. The tripwas about ten miles. Midway through it,Zwally told me that he had once seenspy-satellite photos of the region wewere crossing, and that they had shownthat underneath the snow it was full ofcrevasses. Later, when I asked Steffenabout this, he told me that he had hadthe whole area surveyed with bottom-seeking radar, and no crevasses of anynote had been found. I was never surewhich one of them to believe.

Reinstalling Zwally’s G.P.S. receiverentailed putting up a series of poles, aprocess that, in turn, required drillingholes thirty feet down into the ice. Thedrilling was done not mechanically butthermally, using a steam drill that con-sisted of a propane burner, a steel tank to hold snow, and a long rubber hose.Everyone—Steffen, Zwally, the grad-uate students, me—took a turn. Thismeant holding onto the hose while itmelted its way down, an activity reminis-cent of ice fishing.Seventy-five years ago,not far from JAR 1, Alfred Wegener, theGerman scientist who proposed the the-ory of continental drift, died while on ameteorological expedition.He was buriedin the ice sheet, and there is a runningjoke at Swiss Camp about stumbling ontohis body. “It ’s Wegener!” one of the graduate students exclaimed, as the drillworked its way downward.The first holewas finished relatively quickly, at whichpoint everyone decided—prematurely, asit turned out—that it was time for a mid-day snack. Unless a hole stays filled with

water, it starts to close up again, and can’tbe used.Apparently, there were fissures inthe ice,because water kept draining out ofthe next few holes that were tried. Theoriginal plan had been for three holes,but, some six hours later, only two hadbeen drilled, and it was decided that thiswould have to suffice.

Although Zwally had set out to lookfor changes in the ice sheet’s elevation,what he ended up measuring was,poten-tially, even more significant. His G.P.S.data showed that the more the ice sheetmelted the faster it started to move.Thusin the summer of 1996, the ice aroundSwiss Camp moved at a rate of thirteeninches per day, but in 2001 it had sped up to twenty inches per day. The reasonfor this acceleration, it is believed, is that meltwater from the surface makesits way down to the bedrock below,where it acts as a lubricant. (In the pro-cess, it enlarges cracks and forms hugeice tunnels, known as moulins.) Zwally’smeasurements also showed that, in thesummer, the ice sheet rises by about sixinches, indicating that it is floating on acushion of water.

At the end of the last glaciation,the icesheets that covered much of the North-ern Hemisphere disappeared in a mat-ter of a few thousand years—a surpris-ingly short time, considering how long ithad taken them to build up.At one point,about fourteen thousand years ago, theywere melting so fast that sea levels wererising at the rate of more than a foot a decade. Just how this happened is not entirely understood, but the accelerationof the Greenland ice sheet suggests yetanother feedback mechanism: once an ice sheet begins to melt, it starts to flowfaster,which means it also thins out faster,encouraging further melt. Not far fromSwiss Camp, there is a huge river of iceknown as the Jakobshavn Isbrae, whichprobably was the source of the icebergthat sank the Titanic. In 1992, the Jakob-shavn Isbrae flowed at a rate of three anda half miles per hour;by 2003, its velocityhad increased to 7.8 miles per hour.Sim-ilar findings were announced earlier thisyear by scientists measuring the flow ofice streams on the Antarctic Peninsula.

Over the last century, global sea levelshave risen by about half a foot. The mostrecent report of the U.N.’s Intergovern-mental Panel on Climate Change, issuedin 2001, predicts that they will rise any-

where from four inches to three feet by the year 2100. This prediction includes almost no contribution from Greenland or Antarctica; it is based mostly on thephysics of water,which,as it warms up,ex-pands.Two climatologists at PennsylvaniaState University,Richard Alley and ByronParizek, recently issued new predictionsthat take into account the observed ac-celeration of the ice sheets; this effect inGreenland alone, they estimate,will causeup to two and half inches of additionalsea-level rise over the coming century.James Hansen, the NASA official who di-rected one of the initial nineteen-seventiesstudies on the effects of carbon dioxide,has gone much further, arguing that ifgreenhouse-gas emissions are not con-trolled the total disintegration of theGreenland ice sheet could be set in mo-tion in a matter of decades.Although theprocess would take hundreds, perhapsthousands,of years to fully play out,oncebegun it would become self-reinforcing,and hence virtually impossible to stop.In an article published earlier last year inthe journal Climatic Change, Hansen,who is now the head of the Goddard In-stitute for Space Studies, wrote that hehoped he was wrong about the ice sheet,“but I doubt it.”

As it happened, I was at Swiss Campjust as last summer’s global-warming

disaster movie, “The Day After Tomor-row,”was opening in theatres.One night,Steffen’s wife called on the camp’s satel-lite phone to say that she had just takenthe couple’s two teen-age children to seeit. Everyone had enjoyed the film, shereported, especially because of the fam-ily connection.

The fantastic conceit of “The DayAfter Tomorrow” is that global warm-ing produces global freezing. At the startof the film, a chunk of Antarctic ice thesize of Rhode Island suddenly melts.(Something very similar to this actuallyhappened in March, 2002, when theLarsen B ice shelf collapsed.) Most ofwhat follows—an instant ice age,cyclonicwinds that descend from the upper atmo-sphere—is impossible as science but notas metaphor.The record preserved in theGreenland ice sheet shows that over thelast hundred thousand years temperatureshave often swung wildly—so often that itis our own relatively static experience ofclimate that has come to look exceptional.

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Nobody knows what caused the sud-den climate shifts of the past; however,many climatologists suspect that they hadsomething to do with changes in ocean-current patterns that are known as thethermohaline circulation.

“When you freeze sea ice, the salt ispushed out of the pores, so that the saltywater actually drains,” Steffen explainedto me one day when we were standing outon the ice, trying to talk above the howl ofthe wind.“And salty water’s actually heav-ier, so it starts to sink.”Meanwhile,owingboth to evaporation and to heat loss,water from the tropics becomes denser asit drifts toward the Arctic, so that nearGreenland a tremendous volume of sea-water is constantly sinking toward theocean floor.As a result of this process, stillmore warm water is drawn from the trop-ics toward the poles, setting up what isoften referred to as a “conveyor belt” thatmoves heat around the globe.

“This is the energy engine for theworld climate,” Steffen went on. “And ithas one source: the water that sinks down.And if you just turn the knob here a littlebit”—he made a motion of turning thewater on in a bathtub—“we can expectsignificant temperature changes based onthe redistribution of energy.”One way toturn the knob is to heat the oceans,whichis already happening. Another is to pourmore freshwater into the polar seas. Thisis also occurring. Not only is runoff fromcoastal Greenland increasing; the volumeof river discharge into the Arctic Oceanhas been rising. Oceanographers moni-toring the North Atlantic have docu-mented that in recent decades its watershave become significantly less salty. Atotal shutdown of the thermohaline cir-culation is considered extremely unlikelyin the coming century.But, if the Green-land ice sheet started to disintegrate, thepossibility of such a shutdown could notbe ruled out.Wallace Broecker, a profes-sor of geochemistry at Columbia Uni-versity’s Lamont-Doherty Earth Obser-vatory, has labelled the thermohalinecirculation the “Achilles’ heel of the cli-mate system.” Were it to halt, places likeBritain, whose climate is heavily influ-enced by the Gulf Stream,could becomemuch colder, even as the planet as awhole continued to warm up.

For the whole time I was at SwissCamp, it was “polar day,” and so the sunnever set. Dinner was generally served at

10 or 11 P.M., and afterward everyone sataround a makeshift table in the kitchen,talking and drinking coffee. (Because it isnot—strictly speaking—necessary, alco-hol was in short supply.) One night, Iasked Steffen what he thought condi-tions at Swiss Camp would be like in thesame season a decade hence.“In ten years,the signal should be much more distinct,because we will have added another tenyears of greenhouse warming,” he said.

Zwally interjected,“I predict that tenyears from now we won’t be coming thistime of year. We won’t be able to comethis late. To put it nicely, we are headinginto deep doo-doo.”

Either by disposition or by training,Steffen was reluctant to make specificpredictions,whether about Greenland or,more generally, about the Arctic. Often,he prefaced his remarks by noting thatthere could be a change in atmospheric-circulation patterns that would dampenthe rate of temperature increase oreven—temporarily at least—reverse itentirely. But he was emphatic that “cli-mate change is a real thing.

“It’s not something dramatic now—that’s why people don’t really react,” hetold me.“But if you can convey the mes-

sage that it will be dramatic for our chil-dren and our children’s children—therisk is too big not to care.”

The time, he added, “is already fivepast midnight.”

On the last night that I spent at SwissCamp, Steffen took the data he haddownloaded off his weather station and,after running them through various pro-grams on his laptop, produced the meantemperature at the camp for the previousyear. It was the highest of any year sincethe camp was built.

That night,dinner was unusually late.On the return trip of another pole-drillingexpedition, one of the snowmobiles hadcaught on fire, and had to be towed backto camp. When I finally went out to mytent to go to bed, I found that the snowunderneath it had started to melt, andthere was a large puddle in the middle of the floor. I got some paper towels andtried to mop it up, but the puddle wastoo big, and eventually I gave up.

No nation takes a keener interest inclimate change, at least on a per-

capita basis, than Iceland. More than tenper cent of the country is covered by gla-ciers, the largest of which, Vatnajökull,

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“I’m old enough to recognize a lecture disguised as grace.”

stretches over thirty-two hundred squaremiles. During the so-called Little IceAge, the advance of the glaciers causedwidespread misery; it has been esti-mated that in the mid-eighteenth centurynearly a third of the country’s popula-tion died of starvation or associated ills.For Icelanders, many of whom can tracetheir genealogy back a thousand years,this is considered to be almost recent history.

Oddur Sigurdsson heads up a groupcalled the Icelandic Glaciological So-ciety. One day last fall, I went to visit him in his office, at the headquarters ofIceland’s National Energy Authority,in Reykjavík. Little towheaded childrenkept wandering in to peer under hisdesk. Sigurdsson explained that Reyk-javík’s public schoolteachers were onstrike, and his colleagues had had tobring their children to work.

The Icelandic Glaciological Society iscomposed entirely of volunteers. Everyfall, after the summer-melt season hasended, they survey the size of the coun-try’s three hundred-odd glaciers and thenfile reports, which Sigurdsson collects inbrightly colored binders. In the organiza-tion’s early years—it was founded in1930—the volunteers were mostly farm-ers; they took measurements by building

cairns and pacing off the distance to theglacier’s edge.These days,members comefrom all walks of life—one is a retiredplastic surgeon—and they take more ex-acting surveys, using tape measures andiron poles. Some glaciers have been inthe same family, so to speak, for genera-tions.Sigurdsson became head of the so-ciety in 1987, at which point one volun-teer told him that he thought he wouldlike to relinquish his post.

“He was about ninety when I realizedhow old he was,” Sigurdsson recalled.“His father had done this at that place be-fore and then his nephew took over forhim.” Another volunteer has been moni-toring his glacier, a section of Vatnajökull,since 1948.“He’s eighty,”Sigurdsson said.“And if I have some questions that go be-yond his age I just go and ask his mother.She’s a hundred and seven.”

In contrast to glaciers in North Amer-ica, which have been shrinking steadilysince the nineteen-sixties, Iceland’s gla-ciers grew through the nineteen-seventiesand eighties.Then, in the mid-nineteen-nineties, they, too, began to decline, atfirst slowly and then much more rapidly.Sigurdsson pulled out a notebook ofglaciological reports, filled out on yellowforms, and turned to the section on a glacier called Sólheimajökull, a tongue-

shaped spit of ice that sticks out from amuch larger glacier, called Myrdalsjökull.In 1996, Sólheimajökull crept back byten feet. In 1997, it receded by anotherthirty-three feet, and in 1998 by ninety-eight feet.Every year since then, it has re-treated even more. In 2003, it shrank bythree hundred and two feet and in 2004by two hundred and eighty-five feet. Alltold, Sólheimajökull—the name means“sun-home glacier”and refers to a nearbyfarm—is now eleven hundred feet shorterthan it was just a decade ago. Sigurds-son pulled out another notebook, whichwas filled with slides.He picked out somerecent ones of Sólheimajökull. The gla-cier ended in a wide river. An enormousrock, which Sólheimajökull had depos-ited when it began its retreat, stuck outfrom the water, like the hull of an aban-doned ship.

“You can tell by this glacier what theclimate is doing,” Sigurdsson said. “It ismore sensitive than the most sensitivemeteorological measurement.”He intro-duced me to a colleague of his, KristjanaEythórsdóttir, who, as it turned out, wasthe granddaughter of the founder of theIcelandic Glaciological Society.Eythórs-dóttir keeps tabs on a glacier named Lei-darjökull, which is a four-hour trek fromthe nearest road. I asked her how it wasdoing.“Oh,it’s getting smaller and smaller,just like all the others,” she said. Sigurds-son told me that climate models pre-dicted that by the end of the next centuryIceland would be virtually ice-free. “Wewill have small ice caps on the highestmountains, but the mass of the glacierswill have gone,”he said. It is believed thatthere have been glaciers on Iceland for thelast few million years. “Probably longer,”Sigurdsson said.

In October, 2000, in a middle school in Barrow, Alaska, officials from the

eight Arctic nations—the U.S., Russia,Canada, Denmark, Norway, Sweden,Finland, and Iceland—met to talk aboutglobal warming. The group announcedplans for a three-part, two-million-dollar study of climate change in the region. This past fall, the first two partsof the study—a massive technical doc-ument and a hundred-and-forty-pagesummary—were presented at a sympo-sium in Reykjavík.

The day after I went to talk to Sig-urdsson, I attended the symposium’s ple-

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70 THE NEW YORKER, APRIL 25, 2005

“How many miles before our next fight?”

• •

nary session. In addition to nearly threehundred scientists, it drew a sizable con-tingent of native Arctic residents—rein-deer herders, subsistence hunters, andrepresentatives of groups like the Inu-vialuit Game Council. In among theshirts and ties, I spotted two men dressedin the brightly colored tunics of theSami and several others wearing seal-skin vests. As the session went on, thesubject kept changing—from hydrol-ogy and biodiversity to fisheries and onto forests.The message, however, stayedthe same. Almost wherever you looked,temperatures in the Arctic were rising,and at a rate that surprised even thosewho had expected to find clear signs ofclimate change.Robert Corell, an Amer-ican oceanographer and a former assis-tant director at the National ScienceFoundation, coördinated the study. Inhis opening remarks, he ran through itsfindings—shrinking sea ice, receding gla-ciers, thawing permafrost—and summedthem up as follows: “The Arctic climateis warming rapidly now, with an em-phasis on now.” Particularly alarming,Corell said, were the most recent datafrom Greenland, which showed the icesheet melting much faster “than wethought possible even a decade ago.”

Global warming is routinely de-scribed as a matter of scientific debate—a theory whose validity has yet to bedemonstrated. This characterization, orat least a variant of it, is offered most sig-nificantly by the Bush Administration,which maintains that there is still in-sufficient scientific understanding to jus-tify mandatory action.The symposium’sopening session lasted for more than ninehours. During that time, many speakersstressed the uncertainties that remainabout global warming and its effects—on the thermohaline circulation, on thedistribution of vegetation, on the sur-vival of cold-loving species, on the fre-quency of forest fires. But this sort ofquestioning, which is so basic to scien-tific discourse, never extended to the re-lationship between carbon dioxide andrising temperatures. The study’s execu-tive summary stated, unequivocally, thathuman beings had become the “domi-nant factor” influencing the climate.During an afternoon coffee break, Icaught up with Corell. “Let’s say thatthere’s three hundred people in thisroom,” he told me. “I don’t think you’ll

find five who would say that globalwarming is just a natural process.”

The third part of the Arctic-climatestudy, which was still unfinished at thetime of the symposium,was the so-called“policy document.” This was supposed to outline practical steps to be taken in re-sponse to the scientific findings, includ-ing—presumably—reducing greenhouse-gas emissions. The policy documentremained unfinished because Americannegotiators had rejected much of the language proposed by the seven otherArctic nations. (A few weeks later, theU.S. agreed to a vaguely worded state-ment calling for “effective”—but notobligatory—actions to combat the prob-lem.) This recalcitrance left those Amer-icans who had travelled to Reykjavík in an awkward position. A few tried—half-heartedly—to defend the Administra-tion’s stand to me; most, including manygovernment employees,were critical of it.At one point, Corell observed that theloss of sea ice since the late nineteen-seventies was equal to “the size of Texasand Arizona combined. That analogywas made for obvious reasons.”

That evening, at the hotel bar, I talkedto an Inuit hunter named John Keogak,who lives on Banks Island, in Canada’sNorthwest Territories, some five hundredmiles north of the Arctic Circle. He toldme that he and his fellow-hunters hadstarted to notice that the climate waschanging in the mid-eighties.A few yearsago, for the first time, people began to seerobins, a bird for which the Inuit in his re-gion have no word.

“We just thought,Oh,gee, it’s warm-ing up a little bit,” he recalled. “It wasgood at the start—warmer winters, youknow—but now everything is going sofast. The things that we saw coming inthe early nineties, they’ve just multiplied.

“Of the people involved in globalwarming, I think we’re on top of the listof who would be most affected,”Keogakwent on.“Our way of life, our traditions,maybe our families. Our children may

not have a future. I mean, all young peo-ple, put it that way. It’s just not happen-ing in the Arctic. It’s going to happen all over the world. The whole world isgoing too fast.”

The symposium in Reykjavík lastedfor four days. One morning, when thepresentations on the agenda included“Char as a Model for Assessing ClimateChange Impacts on Arctic Fishery Re-sources,” I decided to rent a car and take adrive. In recent years, Reykjavík has beenexpanding almost on a daily basis, and theold port city is now surrounded by ringsof identical, European-looking suburbs.Ten minutes from the car-rental place,these began to give out, and I found my-self in a desolate landscape in which therewere no trees or bushes or really even soil.The ground—fields of lava from somedefunct, or perhaps just dormant, volca-noes—resembled macadam that had re-cently been bulldozed. I stopped to get acup of coffee in the town of Hveragerdi,where roses are raised in greenhousesheated with steam that pours directly outof the earth. Farther on, I crossed intofarm country; the landscape was still tree-less, but now there was grass, and sheepeating it. Finally, I reached the sign forSólheimajökull, the glacier whose retreatOddur Sigurdsson had described to me. Iturned off onto a dirt road. It ran along-side a brown river, between two crazilyshaped ridges.After a few miles, the roadended, and the only option was to con-tinue on foot.

By the time I got to the lookout overSólheimajökull, it was raining. In thegloomy light, the glacier looked forlorn.Much of it was gray—covered in a filmof dark grit. In its retreat, it had left be-hind ridged piles of silt. These were jetblack and barren—not even the toughlocal grasses had had a chance to takeroot on them. I looked for the enormousboulder I had seen in the photos in Sig-urdsson’s office. It was such a long wayfrom the edge of the glacier that for amoment I wondered if perhaps it hadbeen carried along by the current. A rawwind came up, and I started to headdown. Then I thought about what Sig-urdsson had told me. If I returned inanother decade, the glacier would prob-ably no longer even be visible from theridge where I was standing. I climbedback up to take a second look. ♦

(This is the first part of a three-part article.)

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