When your Jeep
spins lazily off the mountain road and slams backward into a snowbank,
you don’t worry immediately about the cold. Your first thought is
that you’ve just dented your bumper. Your second is that you’ve
failed to bring a shovel. Your third is that you’ll be late for
dinner. Friends are expecting you at their cabin around eight for
a moonlight ski, a late dinner, a sauna. Nothing can keep you from
of town, defroster roaring, you barely noted the bank thermometer
on the town square: minus 27 degrees at 6:36. The radio weather
report warned of a deep mass of arctic air settling over the region.
The man who took your money at the Conoco station shook his head
at the register and said he wouldn’t be going anywhere tonight if
he were you. You smiled. A little chill never hurt anybody with
enough fleece and a good four-wheel-drive.
But now you’re
stuck. Jamming the gearshift into low, you try to muscle out of
the drift. The tires whine on ice-slicked snow as headlights dance
on the curtain of frosted firs across the road. Shoving the lever
back into park, you shoulder open the door and step from your heated
capsule. Cold slaps your naked face, squeezes tears from your eyes.
You check your
watch: 7:18. You consult your map: A thin, switchbacking line snakes
up the mountain to the penciled square that marks the cabin.
from you in short frosted puffs. The Jeep lies cocked sideways in
the snowbank like an empty turtle shell. You think of firelight
and saunas and warm food and wine. You look again at the map. It’s
maybe five or six miles more to that penciled square. You run that
far every day before breakfast. You’ll just put on your skis. No
There is no
precise core temperature at which the human body perishes from cold.
At Dachau’s cold-water immersion baths, Nazi doctors calculated
death to arrive at around 77 degrees Fahrenheit. The lowest recorded
core temperature in a surviving adult is 60.8 degrees. For a child
it’s lower: In 1994, a two-year-old girl in Saskatchewan wandered
out of her house into a minus-40 night. She was found near her doorstep
the next morning, limbs frozen solid, her core temperature 57 degrees.
less fortunate, even in much milder conditions. One of Europe’s
worst weather disasters occurred during a 1964 competitive walk
on a windy, rainy English moor; three of the racers died from hypothermia,
though temperatures never fell below freezing and ranged as high
But for all
scientists and statisticians now know of freezing and its physiology,
no one can yet predict exactly how quickly and in whom hypothermia
will strike – and whether it will kill when it does. The cold
remains a mystery, more prone to fell men than women, more lethal
to the thin and well muscled than to those with avoirdupois, and
least forgiving to the arrogant and the unaware.
begins even before you leave the car, when you remove your gloves
to squeeze a loose bail back into one of your ski bindings. The
freezing metal bites your flesh. Your skin temperature drops.
Within a few
seconds, the palms of your hands are a chilly, painful 60 degrees.
Instinctively, the web of surface capillaries on your hands constrict,
sending blood coursing away from your skin and deeper into your
torso. Your body is allowing your fingers to chill in order to keep
its vital organs warm.
your gloves, noticing only that your fingers have numbed slightly.
Then you kick boots into bindings and start up the road.
Were you a
Norwegian fisherman or Inuit hunter, both of whom frequently work
gloveless in the cold, your chilled hands would open their surface
capillaries periodically to allow surges of warm blood to pass into
them and maintain their flexibility. This phenomenon, known as the
hunter’s response, can elevate a 35-degree skin temperature to 50
degrees within seven or eight minutes.
adaptations to the cold are more mysterious. Tibetan Buddhist monks
can raise the skin temperature of their hands and feet by 15 degrees
through meditation. Australian aborigines, who once slept on the
ground, unclothed, on near-freezing nights, would slip into a light
hypothermic state, suppressing shivering until the rising sun rewarmed
You have no
such defenses, having spent your days at a keyboard in a climate-controlled
office. Only after about ten minutes of hard climbing, as your body
temperature rises, does blood start seeping back into your fingers.
Sweat trickles down your sternum and spine.
By now you’ve
left the road and decided to shortcut up the forested mountainside
to the road’s next switchback. Treading slowly through deep, soft
snow as the full moon hefts over a spiny ridgetop, throwing silvery
bands of moonlight and shadow, you think your friends were right:
It’s a beautiful night for skiing – though you admit, feeling
the minus-30 air bite at your face, it’s also cold.
After an hour,
there’s still no sign of the switchback, and you’ve begun to worry.
You pause to check the map. At this moment, your core temperature
reaches its high: 100.8. Climbing in deep snow, you’ve generated
nearly ten times as much body heat as you do when you are resting.
As you step
around to orient map to forest, you hear a metallic pop. You look
down. The loose bail has disappeared from your binding. You lift
your foot and your ski falls from your boot.
You twist on
your flashlight, and its cold-weakened batteries throw a yellowish
circle in the snow. It’s right around here somewhere, you think,
as you sift the snow through gloved fingers. Focused so intently
on finding the bail, you hardly notice the frigid air pressing against
your tired body and sweat-soaked clothes.
that warmed you on the way uphill now works against you: Your exercise-dilated
capillaries carry the excess heat of your core to your skin, and
your wet clothing dispels it rapidly into the night. The lack of
insulating fat over your muscles allows the cold to creep that much
closer to your warm blood.
begins to plummet. Within 17 minutes it reaches the normal 98.6.
Then it slips below.
At 97 degrees,
hunched over in your slow search, the muscles along your neck and
shoulders tighten in what’s known as pre-shivering muscle tone.
Sensors have signaled the temperature control center in your hypothalamus,
which in turn has ordered the constriction of the entire web of
surface capillaries. Your hands and feet begin to ache with cold.
Ignoring the pain, you dig carefully through the snow; another ten
minutes pass. Without the bail you know you’re in deep trouble.
45 minutes later, you find the bail. You even manage to pop it back
into its socket and clamp your boot into the binding. But the clammy
chill that started around your skin has now wrapped deep into your
At 95, you’ve
entered the zone of mild hypothermia. You’re now trembling violently
as your body attains its maximum shivering response, an involuntary
condition in which your muscles contract rapidly to generate additional
It was a mistake,
you realize, to come out on a night this cold. You should turn back.
Fishing into the front pocket of your shell parka, you fumble out
the map. You consulted it to get here; it should be able to guide
you back to the warm car. It doesn’t occur to you in your increasingly
clouded and panicky mental state that you could simply follow your
tracks down the way you came.
And after this
long stop, the skiing itself has become more difficult. By the time
you push off downhill, your muscles have cooled and tightened so
dramatically that they no longer contract easily, and once contracted,
they won’t relax. You’re locked into an ungainly, spread-armed,
manage to maneuver between stands of fir, swishing down through
silvery light and pools of shadow. You’re too cold to think of the
beautiful night or of the friends you had meant to see. You think
only of the warm Jeep that waits for you somewhere at the bottom
of the hill. Its gleaming shell is centered in your mind’s eye as
you come over the crest of a small knoll. You hear the sudden whistle
of wind in your ears as you gain speed. Then, before your mind can
quite process what the sight means, you notice a lump in the snow
slowly, the danger that you are in, you try to jam your skis to
a stop. But in your panic, your balance and judgment are poor. Moments
later, your ski tips plow into the buried log and you sail headfirst
through the air and bellyflop into the snow.
You lie still.
There’s a dead silence in the forest, broken by the pumping of blood
in your ears. Your ankle is throbbing with pain and you’ve hit your
head. You’ve also lost your hat and a glove. Scratchy snow is packed
down your shirt. Meltwater trickles down your neck and spine, joined
soon by a thin line of blood from a small cut on your head.
you realize with an immediate sense of panic, is serious. Scrambling
to rise, you collapse in pain, your ankle crumpling beneath you.
As you sink
back into the snow, shaken, your heat begins to drain away at an
alarming rate, your head alone accounting for 50 percent of the
loss. The pain of the cold soon pierces your ears so sharply that
you root about in the snow until you find your hat and mash it back
onto your head.
But even that
little activity has been exhausting. You know you should find your
glove as well, and yet you’re becoming too weary to feel any urgency.
You decide to have a short rest before going on.
An hour passes.
at one point, a stray thought says you should start being scared,
but fear is a concept that floats somewhere beyond your immediate
reach, like that numb hand lying naked in the snow. You’ve slid
into the temperature range at which cold renders the enzymes in
your brain less efficient. With every one-degree drop in body temperature
below 95, your cerebral metabolic rate falls off by 3 to 5 percent.
When your core temperature reaches 93, amnesia nibbles at your consciousness.
You check your watch: 12:58. Maybe someone will come looking for
you soon. Moments later, you check again. You can’t keep the numbers
in your head. You’ll remember little of what happens next.
Your head drops
back. The snow crunches softly in your ear. In the minus-35-degree
air, your core temperature falls about one degree every 30 to 40
minutes, your body heat leaching out into the soft, enveloping snow.
Apathy at 91 degrees. Stupor at 90.
crossed the boundary into profound hypothermia. By the time your
core temperature has fallen to 88 degrees, your body has abandoned
the urge to warm itself by shivering. Your blood is thickening like
crankcase oil in a cold engine. Your oxygen consumption, a measure
of your metabolic rate, has fallen by more than a quarter. Your
kidneys, however, work overtime to process the fluid overload that
occurred when the blood vessels in your extremities constricted
and squeezed fluids toward your center. You feel a powerful urge
to urinate, the only thing you feel at all.
By 87 degrees
you’ve lost the ability to recognize a familiar face, should one
suddenly appear from the woods.