Cold (22 page)

The world’s liquid freshwater resides in rivers and lakes, in underground aquifers, and in the sky. Eight-tenths of the world’s
freshwater is frozen. Another three thousand trillion gallons drifts in the atmosphere. But to say that it drifts does not
do it justice. The water cycles through, riding thermals, now as a vapor, now as a droplet, now as a speck of ice coalesced
around a particle of dust nine miles high in the troposphere. It is now in the air as mist, now as rain within a cloud, now
in the Pacific, now as a downpour falling on hot pavement in south Georgia, now on the northern pack ice. It might rise up
from the equator, sink down as a driving rain in the horse latitudes, drift for a while in the Gulf Stream. Rising again to
travel farther north, it eventually makes its way poleward and falls as snow, then melts, running off into the North Atlantic
to follow currents carrying it downward, finding its way to an upwelling, then drifting on the surface until it evaporates
once more, only to wind up God knows where. In geological time, water molecules have been grand travelers, each finding its
way everywhere, touching down everyplace, like irrepressible tourists on a four-and-a-half-billion-year junket.

To understand the movement of water, to understand weather, one has to appreciate the earth for what it is: a spinning round
ball with a rough surface. If the world were flat, facing the sun, receiving equal amounts of sunlight across every square
inch, it would be a simpler place. It is not flat. It is a sphere. A square foot of sunlight hitting the equator at noon spreads
out across a square foot of the earth’s surface, while a square foot of sunlight hitting the earth near the poles, where the
globe curves away and the earth’s surface is turned at an angle to the sun, spreads out over two square feet or three square
feet or ten square feet of the earth’s surface, depending on where one stands. The square foot of light and heat and sustenance
that hits the ground at the equator has to be shared across those multiple square feet at higher latitudes.

Air at the equator, warmed by the sun, rises. Rising air leaves behind an area of low pressure — a low, as it is called. Wind
blows from areas of high pressure to areas of low pressure, performing the singular role of restoring equilibrium, of preventing
too much air from piling up in any one place. But in fulfilling this role, wind transfers heat. Near the surface of the earth,
air rushes in to fill the low, replacing the warm air that has risen. The new air itself warms under the tropical sun and
rises. More air is sucked in. Meanwhile, the rising hot air spreads out as it gains altitude. In spreading out, its pressure
drops, and the heat contained in the air mass spreads out too, making the air mass cooler. The drop in pressure is accompanied
by a drop in temperature. The whole mass spills outward from the equator. Along the way, water vapor carried in the air mass
grows cool enough to condense and tumble downward as liquid water. Around the latitude of Shanghai and Jacksonville in the
Northern Hemisphere and Easter Island and Cape Town in the Southern Hemisphere, and moderated by local geography and the myriad
factors that affect air movements, it tumbles down. George Hadley imagined these global patterns in 1735, before satellites,
before computers, before reasonable maps of the world. The global loops of rising and cooling air near the equator became
known as Hadley cells. Farther north, similar patterns of rising and falling air became known as Ferrel cells and Polar cells.

The earth, spinning, moves beneath the air above it. The air — cycling up and down in Hadley cells and Ferrel cells and Polar
cells, then spilling out north and south in what should be a straight line — is turned by a spinning earth. In the Northern
Hemisphere, the earth’s spin tends to move wind to the right of its direction of travel. In the Southern Hemisphere, the earth’s
spin moves wind to the left of its direction of travel. This effect, this odd rightward and leftward trending of moving air,
was described in 1835 by the Frenchman Gaspard-Gustave de Coriolis and has become known as the Coriolis effect.

But the earth is rough, with mountains and valleys and their attendant shadows. Here on the southern slopes of this mountain,
the sun bathes the earth in warmth, but there in that shadowed valley, the earth is cool. And the ground itself is patchy.
Here on this dull patch of bare dirt, sunlight warms the soil, while there on that patch of snow — on that patch of crystalline
water turned white and smooth to form what amounts to the closest thing nature offers to a perfect reflector — the warmth
bounces off, back into the sky. Under this clear blue sky, the heat is lost, reflected back into space. There under that cloud,
the heat is trapped, held in by a blanket of dust and moisture. This shoreline warms quickly under the morning sun, sending
its air skyward, and the air above the ocean or lake or river blows shoreward to fill what would otherwise become a vacuum.
The air above that black roof is hot, and when it moves skyward, it sucks in air from around the yard, which then is heated
and sent skyward, too. The air is heating and cooling and tumbling about, cells within cells within cells, none of it standing
still for very long, all of it moving with a Coriolis twist.

Even within the simplicity of Hadley cells and Ferrel cells and Polar cells, ignoring the spinning earth and the irregularities
of mountains and reflections from snow, local complexities arise. Superimposed on the simplicity of global patterns is the
nature of fluid dynamics. High in the atmosphere, where warm and cold air meet, vortices form, like the eddies and whirlpools
of fast-flowing rivers, spinning around themselves and floating downstream, confusing the eye by combining directional motion
with spinning and chaotic dancing. The eddies become regions of low pressure, depressions that must be filled. They suck in
air and moisture, pulling it skyward, and high in the sky condensing damp air to rain or snow or sleet or hail and then tossing
it back to the earth.

Wind moves frigid air to warmer climes. It creates blizzards that trap schoolchildren on the prairie. It creates raging gales
into which people walk or sail or ski. It picks up snow that sand-blasts bark from trees.

In the end, weather can be described as a mishmash of events, each one alone predictable, but intermingling to compound one
another and confuse the issue, and in the end adding up to nothing less than a complex mess of unpredictability.

The ancient Babylonians said, “When a halo surrounds the sun, rain will fall. When a cloud grows dark in the sky, the wind
will blow.” Before Socrates, Thales of Miletus made a weather calendar. Aristotle commented on clouds, dew, snow, and hail,
recognizing that they differ because of temperature. The barometer was invented in 1643 and the anemometer, for measuring
wind speed, in 1667. Ben Franklin realized that the weather in Philadelphia came from somewhere else and left for somewhere
else. His attempts to observe a lunar eclipse in 1743 were foiled by storm clouds, but his friends in Boston watched the eclipse
and then, four hours later, watched his storm clouds roll in.

By 1846, weather reports transmitted by telegraph could be purchased for between twelve and twenty-five cents a day. During
the Crimean War, the warship
Henri IV
was lost in a storm on November 14, 1854, and Urbain Leverrier, director of the Paris Observatory, urged the French government
to recognize the need for improved weather forecasting. A year later, in the United States, the Smithsonian was posting weather
maps in its Great Hall. Networks of weather reporters — some paid, some amateurs — sent information on local conditions to
central repositories. A man wearing a raincoat and carrying an umbrella might sit on a park bench in the city, studying the
contents of a rain gauge, while another might record temperatures on Texas rangelands from the back of his horse. A third
might measure the wind blowing in off a busy harbor, and a fourth might record the presence of morning dew on his cornfield.
And then, with all of these observers working, with all of them piping in information through more than twenty thousand miles
of telegraph wires, Adolphus Greely, not long back from the Arctic, failed to effectively foresee the Blizzard of 1888, the
School Children’s Blizzard, predicting instead a cold wave with snowdrifts. The failure left nineteen-year-old Etta Shattuck
alone for three days, bivouacked in a haystack, singing hymns and praying while the storm raged, saved from the haystack only
to die from the infections that followed frostbite. The failure left a seventeen-year-old girl frozen to death standing up.
Because of the failure, the bodies of the Kaufmann brothers, who died huddled like penguins trying to stay warm, had to be
thawed in front of a woodstove before they could be separated.

Vilhelm Bjerknes, a Norwegian working at the beginning of the twentieth century, was the first to propose the application
of thermodynamics and fluid mechanics to the atmosphere. His thoughts evolved to rely on a system of cells, stacked one above
the other and covering the entire earth in nothing less than a three-dimensional checkerboard. The idea was to populate the
three-dimensional checkerboard with data from observations and then use the data to predict what would happen next.

During World War I, the English meteorologist Lewis Fry Richardson tackled the rat’s nest of calculations needed for numerical
forecasting. In 1922, he published a book saying that the calculations would require sixty-four thousand people working day
and night to keep up with the weather. He envisioned a city of workers in a building laid out to mimic the globe itself, with
each of the workers struggling through his equations in a space representing his part of the globe. There would be green space
outside, soccer fields and lakes. Those who predicted the weather, Richardson believed, should have the opportunity to experience
it. In the end, though, the city was never built. It turns out that this decision was justified. Had the city been built,
it would have failed in its purpose, doomed from the outset by a naive belief in a strictly deterministic universe.

The Americans were the first to use electronic computers in weather prediction, in the 1950s. The data, one might think, would
be adequate: more than ten thousand weather stations check conditions around the globe, another five thousand ships and planes
send in information, unmanned buoys transmit data from remote reaches of the world’s oceans, more than a thousand weather
balloons go up each day to sample the sky, and satellites circle endlessly with their gaze turned back toward earth. But the
data are not adequate. In 1963, Edward Lorenz set up weather models on a computer. He compared models run with data offering
three decimal points of accuracy and those run with data offering six decimal points of accuracy. The results were completely
different. Tiny differences in the starting point resulted in major differences at the end point. It would be comparable to
a banker counting his wealth in dollars and in pennies, only to discover that he was well positioned in dollars but flat broke
in pennies. It made no sense. It led to what was later called chaos theory. Lorenz delivered a talk to the American Academy
for the Advancement of Science titled “Predictability: Does the Flap of a Butterfly’s Wings in Brazil Set Off a Tornado in
Texas?” The answer: yes. Or at least it might.

In medieval times, weather predicting was an occult art. Forecasters were burned at the stake.

It is January ninth and twenty below at the Anchorage airport, close to the record cold set in 1952. The ground hides under
four feet of snow, with plowed piles and drifts running deeper. Long icicles hang from roofs. El Niño, where have you gone?

I head south. By the time I fly over the Canadian border, temperatures on the ground are above forty. They hover in the forties
for more than a thousand air miles, and then, as abruptly as a color change on a weather map, they reach the fifties. And
by the time I land in New Orleans, the mercury flirts with seventy. I have flown across almost ninety degrees of temperature
change.