Mountains of Evidence
Thin Ice: Unlocking the Secrets of Climate in the World's
Highest Mountains. Mark Bowen. xiv + 463 pp. Henry Holt and
Company, 2005. $30.
In the summer of 1997, a magazine editor telephoned science writer
Mark Bowen to invite him to join paleoclimatologist Lonnie Thompson
on the summit of Nevado Sajama, the highest peak in Bolivia (some
6,500 meters above sea level). Bowen, an experienced alpinist with a
doctorate in physics, accepted the invitation and linked up with
Thompson and his intrepid band just as their ice-drilling equipment
was reaching bedrock. The two long ice cores that Thompson's group
removed from Sajama were at the time the highest-elevation ice
records ever recovered. The year-by-year layering preserved in those
ice cores (and in others that have been obtained at high-altitude
locations in the tropics) yielded information about the climate in
the ancient past—information that has fundamentally changed
our view of how Earth's climate system works.
Bowen went on to accompany Thompson on other expeditions, including
one to Mount Kilimanjaro in East Africa. In Thin Ice, Bowen
has woven accounts of these journeys into a highly readable tale
that is equal parts scientific biography, adventure story and
history of the science of climate change.
Thompson is a professor of geological sciences at Ohio State
University, where he is affiliated with the famed Byrd Polar
Research Center. In 1983, he led an expedition of 10 people and a
few dozen pack animals to the top of the Quelccaya ice cap in the
high Peruvian Andes, where his team removed the first deep ice core
ever taken from a tropical glacier. Before that point, drilling into
ice caps at high altitudes in the tropics and subtropics had been
considered technically unfeasible and scientifically misguided.
Willi Dansgaard, one of the founding fathers of ice drilling in
polar regions, once told the National Science Foundation in a review
of one of Thompson's funding proposals that "Quelccaya is too
high for human beings, and the technology does not exist to drill
it." Furthermore, back in 1983 it was widely believed that the
tropics were climatically stable and were largely uninvolved in
climate change. Thompson's results from Quelccaya, however, along
with his later data from ice caps elsewhere in the Andes, at several
sites on the Tibetan Plateau, and in Africa have convincingly shown
that the tropics are climatically volatile, as much so as the poles.
In 2001, Thompson made headlines around the world with his
announcement that over the course of the 20th century Kilimanjaro
had lost 80 percent of its ice cover, and with his prediction that
the remaining ice on the summit would be completely gone by about
2015. On repeat visits to Quelccaya and trips to the remaining ice
caps in the tropics, he has documented dramatic melting, which is
among the most visible and compelling evidence of global warming.
Thompson sees himself as racing against time to recover
irreplaceable climate records from the world's rapidly disappearing
In his efforts to obtain ice cores, Thompson has spent an enormous
amount of time at elevations above 5,500 meters. High-altitude
climbers typically tackle a peak by spending time in a series of
camps at lower elevations to acclimatize and then making a final
rushed push for the summit. But Thompson and his loyal band of
colleagues, students and mountain guides spend literally months at a
time working at altitude. The work is strenuous and not without
danger. For example, during one particularly nasty storm near the
top of Huascarán, Peru's highest peak (more than 6,000 meters
above sea level), gale-force winds toppled Thompson's tent with him
inside, and it began sliding across the frozen surface toward a
sheer precipice. With the help of a team member, he avoided plunging
over the edge by jamming an ice ax through the floor of the tent.
More mundane hardships, including altitude sickness, frostbite and
sunburn, have of course also plagued his group.
Historically, drilling programs in Greenland and the Antarctic have
been undertaken with massive logistical support—the use of
military transport aircraft, convoys of tracked vehicles and the
like. In contrast, Thompson and his colleagues have managed to drill
into tropical glaciers with nothing more to rely on than a
combination of modest funding, low-tech equipment, ingenuity and
sheer muscle power. Because the thin air at high altitudes precludes
the use of helicopters, all of the drilling equipment and supplies
must be carried up and down the slopes by yaks, mules, horses or
humans. Thompson's team has designed special lightweight drills that
can be broken down for transport. They have also shunned heavy
generators and fuel, instead carrying solar panels to the drill site
and mounting them there to harness the power of the Sun.
An additional problem faced by those who drill in the tropics is
that the ice they have collected melts as they descend to warmer
altitudes. Thus they must race to get ice cores off the mountain and
into freezers before shipping them back to a repository at the Byrd
Polar Research Center. A much-publicized effort in 2000 to move ice
cores off the summit of Kilimanjaro using a hot-air balloon was
aborted when the Tanzanian government refused to approve the needed
permits. Thompson had to hire additional porters to carry the cores down.
Although Bowen's narrative is constructed around Thompson's heroic
quest to gain insights into climate behavior, Thin Ice is
also a detailed and impressively researched history of the science
of climate change, from the theoretical underpinnings of greenhouse
science provided in the early 19th century by mathematician Joseph
Fourier and chemist Svante Arrhenius, to the 20th-century insights
and contributions of Guy Stewart Callendar, Roger Revelle and
Charles David Keeling, to the most recent literature on El
Niño and the modeling of changes in ocean circulation.
Fortunately, what could have been a dry litany of scientific
accomplishments is enlivened by tales of personalities and
rivalries, competing ideas and struggles for funding, and political
debates on the floor of Congress. The result is an entertaining and
illuminating account of how science works and of the dangers of its politicization.
A final theme that emerges in Thin Ice is the link between
climate change and human history. As paleoclimatologists like
Thompson have produced increasingly detailed records of changes over
time in temperature and precipitation patterns in the tropics,
anthropologists and historians have begun to examine the
implications of that research for our understanding of the rise and
fall of civilizations. Time after time, dating has produced
compelling correlations that argue for the role of climate change as
a trigger for societal upheaval. The annual layers of the ice cores
from Quelccaya contain evidence of a 300-year-long drought that
began about 1150 A.D., which coincides with the collapse of the
Tiwanaku civilization around Lake Titicaca. In ice from Kilimanjaro,
a prominent dust-rich band indicative of a disastrous drought about
4,200 years ago correlates with the sudden simultaneous collapses of
the Old Kingdom of Egypt and the Akkadian Empire in Mesopotamia.
As human activities are increasingly implicated as the primary cause
of the current rise in global temperature, the realization that
ancient cultures may have succumbed to climate changes may provide
valuable lessons for humanity in the face of an uncertain climate
future. This is a timely message that deserves our attention.
Reading Thin Ice leaves one with an appreciation of how
vulnerable we are to climate change and how important it is for
future generations that we consider now how to avoid contributing to
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