Cold (10 page)

The glacial ice is long gone from Scotland, absent now for thousands of years. But ice still sculpts the landscape. In winter,
pipkrakes churn the soil. Pipkrakes give the collapsing crunch to frozen ground in early winter. They are known by other names:
needle ice and mush frost,
Kammeis
to Germans,
shimobashira
to Japanese. They grow within the soil, from the bottom up, when the temperature drops below freezing. Water in the soil
freezes, and the freezing water sucks more water up from beneath. Vertical crystals grow. They grow as much as half an inch
in a single night. As they grow, they push the soil upward. The churning of the ground pushes the fine-grained soil to the
surface, where it is blown away in areas with high winds, leaving behind shallow hollows and causing what some farmers call
soil deflation. If you are in the business of growing crops, soil deflation deflates your assets. Certain farmers, unable
to bear the thought of blowing assets, compact the ground where pipkrakes form.

Here in the Scottish Highlands, pipkrakes have sculpted steps into the slopes. These steps are anything but subtle. Pipkrakes
lift the smaller grains of soil away from larger pebbles and rocks. At a slower pace, pipkrakes lift the pebbles away from
the rocks, and at an even slower pace, they lift the smaller rocks away from the bigger rocks. In Canada, pipkrakes have lifted
rocks weighing upward of one ton. On steep slopes with scattered vegetation, the fine soil pushed to the top blows away. The
pebbles tumble downslope. The rocks settle back into place. All of this occurs at differing paces. The end result can be solifluction,
the slow and irregular sliding of a hillside. Under the right conditions of soils and slopes and moisture, solifluction leaves
what looks like a regular pattern of cryoturbation steps. These steps sometimes form diamond patterns on the slopes, but they
also form long parallel terraces, each progressively lower platform a step away from and a step below the next. It appears
as if some bored druid or some Iron Age tribe had carved steps up the sides of these mountains.

Moving downward, we take a shortcut across scree, loose rock and gravel splintered by ice. On scree, it is difficult to remain
upright. My companion, her hands still numb from the Raynaud’s, is afraid of falling, rightfully scared because her numb hands
will be little help in breaking the fall. I scurry ahead. Below the scree, I find a hollow of deflated soil that shaves a
notch off the wind and nap while waiting for her to catch up.

Recognition of the Pleistocene Ice Age is a surprisingly recent phenomenon. Two hundred years ago, no one would have suggested
that ice sheets many miles thick had once covered most of Britain, most of Norway and Switzerland, New York City and Boston.
People knew of ice sheets in Greenland, and they were learning about the ice of the far north. James Cook and others had sailed
far enough south to have been stopped by Antarctic ice. They knew of alpine glaciers, and they knew of the huge boulders scattered
around the lowlands — the erratics sitting on top of soil, with no hint of how they might have gotten there, miles from the
nearest source of this sort of rock, far too big to carry. There was some thought that the boulders had been carried there
by ice, but floating ice during the biblical Flood rather than vast ice sheets hundreds or thousands of feet thick and stretching
hundreds of miles to the north. As for other signs of glaciation — the strange hills of soil that would become known as moraines,
the baskets of eggs called drumlins, and the odd scoring often found across the faces of exposed bedrock — they were easy
enough to overlook and ignore.

Charles Darwin, after learning about ice ages, chastised himself and others for missing the obvious. “I had a striking instance
how easy it is to overlook phenomena,” he wrote, “however conspicuous, before they have been observed by anyone…. Neither
of us saw a trace of the wonderful glacial phenomena all around us; we did not notice the plainly scored rocks, the perched
boulders, the lateral and terminal moraines.”

The observer who pointed out the obvious was Louis Agassiz, a Swiss scientist. As a student in Munich, he cataloged fish from
the Amazon for one of his professors. This did not mean traveling to the Amazon itself. Agassiz traveled instead through pickled
samples, sketching whole fish and scales and bones. He explored the vistas of a laboratory bench and named the fish that he
encountered in those wanderings. In 1829, while still a student and despite never having been to Brazil, he published
Brazilian Fishes,
making his first mark as a naturalist. Ten years later, by then widely recognized for his work, Agassiz vacationed near Bex
in the Swiss Alps. There the geologist Jean de Charpentier ran a salt mining operation. Charpentier, in part through his association
with an engineer named Ignatz Venetz, was convinced that the Swiss glaciers had shrunk over time. He took Agassiz to look
at boulders along the faces of existing glaciers, then showed him others farther downhill, dumped there sometime in the past.
They were of a kind of rock that might not occur for miles around, and as often as not they were stuck precariously on valley
walls or left standing in odd positions. They were erratics. The two men also saw curved beds of gravel and earth — moraines
— along the faces of glaciers that matched those farther downslope, and they saw grooves and scratches cut into bedrock.

A year later, in 1837, Agassiz presided over a meeting of the Natural History Society of Switzerland. In his introductory
speech, when he was expected to talk about fossil fish, he sprang the idea of an ice age. Although Charpentier knew that the
alpine glaciers had once covered more of the Alps than they currently did, Agassiz went further. He described a sheet of ice
extending from the North Pole to the Mediterranean. He knew that some would view this as harebrained. “I am afraid,” he said,
“that this approach will not be accepted by a great number of our geologists, who have well-established opinions on this subject,
and the fate of this question will be that of all those that contradict traditional ideas.”

Three years went by before Agassiz published
Études sur les Glaciers
. “In my opinion,” he wrote, “the only way to account for all these facts and relate them to known geological phenomena is
to assume that… the Earth was covered by a huge ice sheet that buried the Siberian mammoths and reached just as far south
as did the phenomenon of erratic boulders.” He was wrong about many things. “The development of these huge ice sheets must
have led to the destruction of all organic life at the Earth’s surface,” he wrote. “The land of Europe, previously covered
with tropical vegetation and inhabited by herds of great elephants, enormous hippopotami, and gigantic carnivore, was suddenly
buried under a vast expanse of ice, covering plains, lakes, seas, and plateaus alike.” In fact, the Ice Age was not sudden,
it did not bury all of Europe under ice, and it did not destroy all organic life, but his general premise was correct. Made
famous by this premise, he moved to the United States to take a professorship at Harvard. He died in 1873 and was buried in
Cambridge, Massachusetts, under a granite erratic shipped from a moraine in Switzerland. Its transport across the Atlantic
made it the most erratic of erratics. By that time — nearly six decades after the Year Without Summer and Shelley’s
Frankenstein,
a few years before Greely and a handful of his men barely survived their experience in the Arctic, and fifteen years before
the School Children’s Blizzard — the existence of a great ice age was considered a fact. The world knew of the Pleistocene
glaciations.

Speculations about the cause of the Ice Age abounded. James Croll, a self-educated Scotsman who had run a tea shop and worked
as a millwright before becoming known for his scientific contributions, wrote, “We may describe, arrange, and classify the
effects as we may, but without a knowledge of the laws of the agent we can have no rational unity.” Some thought that the
sun might change over time. Others wondered if the earth might occasionally drift through cold regions of space. Some thought
that the earth might have somehow rolled, so that the poles were at the equators. But Croll built his work on a proposal put
forward in Charles Lyell’s famous
Principles of Geology
in 1830. Lyell had skeptically suggested that someone should look into the possible influence of astronomical conditions.
Someone, Lyell had suggested, should do the math. Croll decided that he was the someone for the job.

This was in a time before computers, but it was known that the earth’s orbit was elliptical and that the ellipse changed over
time. As other planets tugged at the earth, its orbit could become more round or more stretched. When its orbit was stretched,
the earth would be farther from the sun during the winter and might receive less light. It was also known that the earth’s
axis was tilted; the earth leaned at an angle to the sun, making winter days shorter than summer days. More important for
Croll, it was known that the earth’s axis wobbled over time. And Croll knew that periods of extensive glaciation during the
Ice Age had in fact come and gone and come and gone through repeated cycles, that the Ice Age was not a single event but rather
a pattern of events that had to be explained. Building on the work of others, he looked for a cause that could explain these
cycles of relative cold and relative warmth, or more correctly, relative cold and relatively less cold. He saw that the combination
of changes in the earth’s orbit and a wobbling axis would lead to at least mild changes in the heat coming into the Northern
Hemisphere. He realized that slight cooling could mean more snow. He knew snow to be a nearly perfect reflector of heat. On
a cold, clear day, warmth from the sun that hits snow is reflected back into the air and lost. And he believed that as glaciers
grew, wind patterns would change and that this could lead to changes in oceanic currents.

Croll had many of the facts correct, but his timing was off. As geologists learned more about the coming and going of cold,
they saw that the cycles from Croll’s work did not match what they saw on the ground. Croll’s math was out of kilter with
the earth’s behavior, and his ideas were discarded. But, as sometimes happens in science, his ideas were later resurrected.
Milutin Milankovitch, a Serbian mathematician and engineer known as an authority on the properties of concrete, decided that
his talents could best be used in developing a mathematical theory of the earth’s climate. Working through the chaos of the
First World War, spending part of that time as a prisoner of war, using new information on just how much energy the sun delivers
to the earth, Milankovitch reworked what Croll had started. In 1920, he wrote
A Mathematical Theory of the Thermal Phenomena Produced by Solar Radiation,
a book with a title that doomed it to limited circulation. But among the few readers of the book was Wladimir Köppen. Köppen’s
daughter was married to Alfred Wegener, the man responsible for the theory of continental drift, who would later, in a historical
footnote, die on the Greenland ice. Köppen and Wegener realized that Milankovitch’s work could be extended to the distant
past. They wanted him to run the calculations to six hundred thousand years before the present. The results were consistent
with the history of the Ice Age as it was then understood. In 1941, Milan kovitch published another book with another catchy
title,
Canon of Insolation and the Ice Age Problem
. The Second World War broke out. The manuscript was at the printer when the Germans invaded Yugoslavia. The printing shop
was flattened, but the manuscript survived more or less intact and was printed and distributed during the German occupation.
From the memoirs of Milankovitch: “Our civilized existence had disintegrated into a life of hard grind.”

Like Croll’s work, Milankovitch’s efforts were eventually dismissed. In a repeat of Croll’s situation, new evidence suggested
that the timing from Milankovitch’s models did not match what had happened on the ground. But the parallel with Croll extended
to the resurrection of Milankovitch’s work. In 1976, a trio of scientists showed that the on-the-ground record matches a set
of overlaid astronomical cycles: changes in the earth’s orbit over a hundred-thousand-year cycle, changes in the earth’s tilt
over a forty-three-thousand-year cycle, and wobble of the earth’s tilt over a twenty-thousand-year cycle combine to correspond
to some degree with what is known about climate history during the hundreds of thousands of years of the Pleistocene Ice Age.

Circle the earth in late winter, and what do you see? In the Northern Hemisphere, half the land is covered with snow, and
a third of the ocean is frozen. We are in the midst of a warm spell, we are worried about global warming, but the fact remains
that even in summer, whole regions remain covered with snow and ice. An area of land five times the size of Texas is in the
permafrost zone, underlain by permanently frozen ground. If the mathematical predictions are right, we are at the tail end
of an interglacial period, dramatically increasing its warmth with greenhouse gas emissions. But nevertheless we remain in
what a geologist one hundred thousand years in the future would clearly recognize as part of the Pleistocene Ice Age. If the
Ice Age does not die a natural death, and we do not kill it with greenhouse gases, renewed glaciation will come within a few
thousand years.