So you survive. But you’ve been to a very cold place, a place that most people don’t experience. You’ve taken the absolute cold into your body, and the mark of winter will be left at the tip of your nose, which you will lose to frostbite, along with the tip of one of your fingers. You have experienced what few of us really understand: that we exist in an illusion of warmth. No matter where we live on this planet, in the steaming equatorial rainforests of the Amazon or the wincing heat of the Sahara, a bone-chilling temperature of -20°C is never further than 26,000 feet away — straight up. And up just gets colder. The average temperature of interstellar space is -270°C. Warmth is the exception in this universe.
The Coldness of Winter
“Behold the frostwork on the pane — the wild, fantastic limnings and etchings! Can there be any doubt but this subtle agent has been here! Where is it not? It is the life of the crystal, the architect of the flake, the fire of the frost, the soul of the sunbeam. This crisp winter air is full of it. When I come in at night after an all-day tramp I am charged like a Leydon jar; my hair crackles and snaps beneath the comb like a cat’s back, and a strange, new glow diffuses itself through my system.”
John Burroughs
“In the bleak midwinter
Frosty wind made moan,
Earth stood hard as iron,
Water like a stone;
Snow had fallen,
Snow on snow,
Snow on snow,
In the bleak midwinter,
Long ago.”
Christina Rossetti
More than a decade ago, I visited Tobago, an island in the Caribbean just off the coast of Venezuela. There, in the coastal village of Bucco, I befriended a local skipper, a fisherman by the name of David, who piloted the glass-bottom boat out to the reef. He was fascinated by my stories about Canada and he seemed particularly interested in my descriptions of winter, about the intensity of the cold. By way of personal experience, he recounted how he had been at the top of a high hill in Tobago one evening and it was so cold he saw his breath. Was that like the winter in Canada?
I told him that seeing your breath was just the beginning. “You know the freezer compartment in a refrigerator?” I said. “That’s winter. That’s what it’s like outdoors in January. It’s so cold that everything is frozen rock hard, the earth, the lakes and the leafless trees.” I could see he was impressed, though there was a slight sense of incredulity to his amazement; after all, he was a reasonable person. How did people survive in such an extreme climate, and why on earth would they build cities that far north?
Sitting on the beach in Tobago, you’d never guess that we were in the middle of an ice age, but we are. If we weren’t, no snow would fall anywhere, not even in the Arctic. Any period of Earth’s history where ice covers one of the poles is considered an ice age, and the current one is called the Pliocene-Quaternary glaciation. Right now, massive glaciers cover Greenland, most of the Arctic islands and the entire continent of Antarctica. They also lurk at the summits of many mountains, waiting to pounce. Indeed, one large mountain glacier has the audacity to dwell on the equator, atop Chimborazo in Equador.
It will stay put, probably for thousands of years, because our ice age, which began less than four million years ago, is characterized by alternating periods of cooler and warmer climates. The colder periods, when the continental glaciers expand, are called stadials, and the relatively warm periods, when the glaciers retreat, are called interstadials. Currently we are enjoying a moderately warm interstadial period, although it’s nowhere near as warm as the last one, the Sangamonian interglacial, which peaked about 120,000 years ago, around the time when our species, Homo sapiens, began to expand north from South Africa.
But if we got started during a warm interstadial period, we came of age during a major glaciation event, the Wisconsin glaciation. Winter shaped our species. Our versatile and playful minds grasped the frictionless potential of ice and snow, and we used it. Long before the wheel was invented, snow sleds were common in northern Europe. A flat board, or two runners, placed under a load made it much easier to drag over the snow. It is likely that Cro-Magnons wore something like skis to to pursue game, and fragments of wooden skis dating back to 6,000 BCE have been discovered in northern Russia. But likely even earlier than that, in eastern North America, the indigenous people developed my favorite winter sport — snowsnakes — which is played to this day.
In the coldest week of February, the small town of Brantford in southern Ontario plays host to a gathering of the Six Nations: the Mohawk from upstate New York, the Cayuga, Tuscarora, Onondaga and Oneida from Ontario, the Seneca from Michigan as well as the Delaware from Ohio. There they compete in the annual winter tournament of snowsnakes. The snakes themselves are exquisitely honed and lacquered wooden lances, some six feet long, whose snake-like heads are inlaid with finely wrought intaglios of metal. These lances are hurled with professional skill onto a narrow luge track that stretches more than a mile and a half. Whoever’s snowsnake goes the farthest is the winner.
Speed is winter’s gift. I can remember February weekends when all the kids on my street were tobogganing down the highest hill in the neighborhood. If they didn’t have a sled or a toboggan, a piece of cardboard would do. We also had a frozen pond for hockey games. I used to skate all afternoon there, until my feet were numb. I was continuing a tradition, it turns out, thousands of years old. Five-thousand-year-old bone skates have been uncovered by archeologists in Scandinavia and Russia. Four and a half millennia later, just in time for the Little Ice Age, the Dutch invented iron skates, similar to the ones we use today.
Previously, during the medieval warm period, which lasted almost 700 years from 800 to 1450 CE, the climate was so balmy that Vikings established farms in Greenland, and England hosted extensive vineyards. Geoffrey Chaucer, who lived from 1343 to 1400, was a product of the last century of the medieval warm period. His grandfather and his father were wealthy vintners who could afford Geoffrey’s education and an entrée into royal court society. The Norse farms and English vineyards ended with the arrival of the Little Ice Age, which lasted 400 years from 1450 to 1850.
Climatologists have a time machine of sorts, one that allows them to see what winters looked like back then. Pieter Bruegel the Elder’s painting The Hunters in the Snow (1565) is one such marvelous window into the period. Two Dutch hunters and a pack of dogs plod through deep snow on a moody, overcast winter day in Holland. Behind them, in the distance, frozen ponds are covered with diminutive skating figures. This scene would be impossible in today’s Netherlands. Hans Neuberger, former head of the department of meteorology at Pennsylvania State University analyzed The Hunters in the Snow and approximately 12,000 other paintings that dated between 1400 and 1967 from European and American museums. Measuring the percentage of cloudiness and darkness in paintings of the outdoors, Neuberger tracked the progress of the Little Ice Age and discovered a peak between 1600 and 1649 that almost exactly coincides with the beginning of the Maunder minimum (1645 to 1710), with the coldest period spanning the 40 years from 1670 to 1710. It is thought that this protracted cold period was caused by a dimming of solar activity characterized by a complete lack of sunspots; hence “minimum.” The eponym “Maunder” is a tribute to solar astronomers Annie Russell Maunder (1868–1947) and her husband, E. Walter Maunder (1851–1928), who were the first to link solar activity to climate change. During the 40 years of the Maunder miniumum, the Thames River froze solidly enough that for decades winter fairs were held regularly on the thick ice.
Toward the end of the Little Ice Age, it was still cold enough to ensure that 1816 was the “year without a summer,” in the United States. New England experienced heavy snowfalls in June, July and August. In Savannah, Georgia, that same year, the Independence Day high was only 8°C. (Of course the concurrent eruption of Mount Tambora in Indonesia didn’t help matters that year.) Yet none of these Little Ice Age minimum temperatures compar
e with Fairbanks, Alaska, in January, where the average daytime high temperature is -18°C, or to one frigid day in February 1947, when the inhabitants of Snag, Yukon, watched their temperature drop to -63°C! But there’s no competition when it comes to the coldest place on Earth — the home turf of the Pleistocene glacial age.
Antarctica
“The squeak of the snow will the temperature show.”
Weather proverb
Antarctica is the heart of winter, with temperatures rivaling the surface of Mars and the entire continent scoured by inhumanly cold winds. Explorers trying to reach the South Pole on foot were the first to battle the dreaded subfreezing katabatic winds, caused by cold air flowing down the continental gradient toward the ocean, gaining speed as they move. Gusting at a more-or-less constant 40 miles per hour, they sometimes pick up to hurricane-strength blasts of 200 miles per hour. Scott’s ill-fated expedition to the South Pole was wiped out by these winds in 1912.
The coldest temperature measured on our planet since we have been keeping records was in Vostok, Antarctica, on July 23, 1983, when the mercury dropped to -89.2°C. Vostock experienced some of its warmest weather during the summer of 2003, when temperatures reached a balmy -32°C. By comparison, among the temperatures that a Viking lander recorded on Mars, the highest was -17.2°C while the lowest was -107°C. So, although the long winter night in Vostok does not rival the deep freeze on Mars, Vostok’s warmest weather can be colder than a Martian summer. Which is not to say that temperatures on Earth have never fallen as low as those on Mars.
Snowball Earth
Imagine you are our time traveler again, this time visiting our planet 600 million years ago. When the time mist clears, you step out of your machine into the middle of a polar landscape, a vast, snowy plain that extends from horizon to horizon. It’s fortunate you packed an Antarctic expedition suit because, even though the sky is a cloudless blue, the outside temperature is -35°C. You scrape at the crust of wind-hardened snow beneath your boots to reveal the icy surface of a frozen ocean. If you drilled through that layer of ice, you’d have to bore down 65 feet before you hit salt water. But you don’t have time for that.
Even through your thermal insulation, you’re beginning to feel the chill. Equally disturbing is the fact that the sun, directly overhead, tells you that you are in the tropics, possibly standing on the equator itself. How could that be? Welcome to Snowball Earth.
Spitsbergen’s Secret
W. Brian Harland was a mid-twentieth century geologist from Cambridge University who specialized in glacial physiography. He had an encyclopedic memory and a reputation for being tenacious, cantankerous and a dogged researcher. He was also a Quaker, yet another in a long line of Quaker scientists. He liked to do his geology in the field, and the Norwegian island of Spitsbergen became his real-world geological laboratory.
From 1938 to 1981, he made dozens of field trips to the island and the surrounding Svalbard archipelago to observe, among other things, “galloping glaciers,” ice-gouged fjords, towering moraines and meltwater sediment. He also explored and collected samples from the bedrock beneath the glacial deposits, and there, in the sedimentary rocks, Harland uncovered a mystery.
Spitsbergen was primarily composed of strata that had been laid down in shallow, tropical seas during the Devonian period. But on the west and north coasts, Harland found much older rocks, sediments laid down in the Precambrian-era tropics. Within these, he discovered tillites, the telltale deposits from glaciers. Problem was, the rock was 600 million years old — much, much older than any known glacial deposits. If these glacial tillites had indeed been formed in the tropics, what were they doing there?
Harland experienced his first intimation of a monstrous, heretical idea. If glaciers had extended all the way to the tropics, then the whole planet must have been frozen. Perhaps there had been a catastrophic, global ice age, one so extreme it made recent glacial ages look like spring frosts. But he needed more evidence, so between field trips to Spitsbergen, he began a search through geological collections from all over the world. He was looking for 600-million-year-old rocks. He was particularly interested in dropstones.
As a glacier scrapes over bedrock, it picks up stone fragments and carries them along. If a glacier melts on land, it leaves piles of ice-rounded stones in drifts called moraines. But if a glacier extends over water, the stones fall beneath the floating glacier to the bottom of the lake or ocean. These are dropstones. And Harland found them everywhere, in every collection of 600-million-year-old rocks from around the world.
His hunch was right: there had been a worldwide ice age. He published his findings in 1963 and braced himself for scientific fame. Instead, his geological colleagues dismissed his theory as ludicrous. The tropics could never freeze, they argued, not now, not 600 million years ago. They insisted that the rocks that Harland had analyzed were not in the tropics when the dropstone layer was formed. Continental drift had carried them far from where they had originally been deposited. Harland’s global deep freeze theory seemed to have come to a dead end. He had to wait more than 20 years before it was resurrected.
More Than a Chance in Hell
In the late 1980s, Joseph Kirschvink at the California Institute of Technology became fascinated by Harland’s theory. As the world’s foremost expert in geomagnetism, Kirschvink was in a unique position to prove or disprove Harland’s global ice age hypothesis. He knew that when a rock is formed, it is permanently imprinted with the direction of the Earth’s magnetic field lines. Rocks that are formed in the tropics have horizontal field lines and those from the Arctic have almost vertical ones. Kirschvink had just constructed an extremely sensitive magnetic field detector in his laboratory, and he decided to put Harland’s theory to the ultimate test. He was prepared for the worst. “Many wonderful, beautiful theories,” he said, “have been slaughtered by a nasty little fact.”
So, like Harland before him, Kirschvink acquired samples of 600-million-year-old dropstone strata from all over the world. He then analyzed them in his geomagnetic detector. What he found astonished him. Many of the rocks had been formed in the tropics. Harland’s vision of a planet-wide ice age of unimaginable proportions was now based on solid evidence. Kirschvink was converted. He coined the term “Snowball Earth” to describe the catastrophic deep freeze that had now, at least in his mind, become an historical fact. A disastrous glacial age had almost ended life on Earth 650 million years before our time. Simple, multicellular organisms that had been thriving for more than a billion years were decimated by this brutal 15-million-year glacial age. The world’s oceans were capped with a layer of ice that was almost a mile thick at the poles and 65 feet thick at the equator. On an unusually warm day in the “tropics” of Snowball Earth, the temperature might have reached a torrid -30°C.
If, during this period, there had been a Martian civilization with astronomical telescopes and a space exploration program, they would never have bothered to send a probe to look for life on Earth. Our planet would have appeared as a small, brilliant white sphere through their telescopes — a barren, hostile desert that had been locked in ice for as long as our hypothetical Martian civilization had existed. No one could have guessed that life was hanging on precariously beneath the ice.
Back to the Drawing Board
But science is a skeptical, often conservative field. As Max Planck once grimly quipped, “Science advances one funeral at a time.” Kirschvink found few allies for his resurrection of Harland’s theory; his critics pointed out that the terrestrial albedo effect, which governs the reflectivity of the Earth and its ability to shed or acquire heat, had two corollaries that damned Harland’s hypothesis. First of all, it was impossible for glaciers to reach the equator, and there was math to prove as much. Second, if glaciers had somehow managed to overrun the tropics and all the oceans had frozen, then terrestrial albedo dictated that there would be no way out of the deep freeze. It would last forever.
Kirsch
vink would not admit defeat. Yes, the balance of seasonal temperatures and terrestrial albedo seemed to rule out the possibility of glaciers extending any further south or north from the poles than 40° latitude (New York City or Tasmania). And certainly, at first, he couldn’t coax any flexibility out of the numbers. But then he had a stroke of luck.
A Russian climatologist by the name of Mikhail Budyko had been studying the effects of nuclear winter. Years before, in the 1960s, Budyko had discovered a terrifying formula, a climatic tipping point that kicked in when half the sun’s heat was reflected away from the Earth by the albedo effect of large glaciers. He proved mathematically that under certain climatic conditions glaciers could reach the latitude of 32° north or south (Houston, Texas, in the northern hemisphere or Santiago, Chile, in the southern hemisphere). This latitude was the point of no return; once a continental glacier crossed this line then runaway ice-albedo feedback would cause catastrophic heat loss. The result would be a planetary freeze. For Kirschvink, Budyko became the white knight of Harland’s theory. Kirschvink contacted him, and within weeks Budyko’s calculations were in his hands. The math was airtight.
Kirschvink was elated. The first flaw had been overcome. Unfortunately that left an even larger question: How the hell did the planet get out of an irreversible deep freeze? How did life survive? Kirschvink wrestled with the problem for months. There had to be an outside force, some vector of climate change he hadn’t thought of. An asteroid impact like the one that wiped out the dinosaurs was a possibility, but dust and ash kicked up by the collision would have cooled the atmosphere even further. There was no evidence of greater solar activity either; if anything, the sun was slightly dimmer than it is today.
18 Miles Page 18
