January 22, 2004-1
Copyright © 2004 Earth Policy Institute
Glaciers and Sea Ice Endangered by Rising
Temperatures
Janet Larsen
By 2020, the snows of Kilimanjaro
may exist only in old photographs. The glaciers in Montana's Glacier
National Park could disappear by 2030. And by mid-century, the Arctic
Sea may be completely ice-free during summertime. As the earth's
temperature has risen in recent decades, the earth's ice cover has
begun to melt. And that melting is accelerating.
In both 2002 and 2003, the Northern Hemisphere
registered record-low sea ice cover. New satellite data show the
Arctic region warming more during the 1990s than during the 1980s,
with Arctic Sea ice now melting by up to 15 percent per decade.
The long-sought Northwest Passage, a dream of early explorers, could
become our nightmare. The loss of Arctic Sea ice could alter ocean
circulation patterns and trigger changes in global climate patterns.
On the opposite end of the globe, Southern
Ocean sea ice floating near Antarctica has shrunk by some 20 percent
since 1950. This unprecedented melting of sea ice corroborates records
showing that the regional air temperature has increased by 2.5 degrees
Celsius (4.5 degrees Fahrenheit) since 1950.
Antarctic ice shelves that existed for thousands
of years are crumbling. One of the world's largest icebergs, named
B-15, that measured near 10,000 square kilometers (4,000 square
miles) or half the size of New Jersey, calved off the Ross Ice Shelf
in March 2000. In May 2002, the shelf lost another section measuring
31 kilometers (19 miles) wide and 200 kilometers (124 miles) long.
Elsewhere on Antarctica, the Larsen Ice
Shelf has largely disintegrated within the last decade, shrinking
to 40 percent of its previously stable size. Following the break-off
of the Larsen A section in 1995 and the collapse of Larsen B in
early 2002, melting of the nearby land-based glaciers that the ice
shelves once supported has more than doubled.
Unlike the melting of sea ice or the floating
ice shelves along coasts, the melting of ice on land raises sea
level. Recent studies showing the worldwide acceleration of glacier
melting indicate that the Intergovernmental Panel on Climate Change's
estimate for sea level rise this centuryranging
from 0.1 meters to 0.9 meterswill
need to be revised upwards. (.)
On Greenland, an ice-covered island three
times the size of Texas, once-stable glaciers are now melting at
a quickening rate. The Jakobshavn Glacier on the island's southwest
coast, which is one of the major drainage outlets from the interior
ice sheet, is now thinning four times faster than during most of
the twentieth century. Each year Greenland loses some 51 cubic kilometers
of ice, enough to annually raise sea level 0.13 millimeters. Were
Greenland's entire ice sheet to melt, global sea level could rise
by a startling 7 meters (23 feet), inundating most of the world's
coastal cities.
The Himalayas contain the world's third
largest ice mass after Antarctica and Greenland. Most Himalayan
glaciers have been thinning and retreating over the past 30 years,
with losses accelerating to alarming levels in the past decade.
On Mount Everest, the glacier that ended at the historic base camp
of Edmund Hillary and Tenzing Norgay, the first humans to reach
the summit, has retreated 5 kilometers (3 miles) since their 1953
ascent. Glaciers in Bhutan are retreating at an average rate of
3040
meters a year. A similar situation is found in Nepal.
As the glaciers melt they are rapidly filling
glacial lakes, creating a flood risk. An international team of scientists
has warned that with current melt rates, at least 44 glacial lakes
in the Himalayas could burst their banks in as little as five years.
Glaciers themselves store vast quantities
of water. More than half of the world's population relies on water
that originates in mountains, coming from rainfall runoff or ice
melt. In some areas glaciers help sustain a constant water supply;
in others, meltwater from glaciers is a primary water source during
the dry season. In the short term, accelerated melting means that
more water feeds rivers. Yet as glaciers disappear, dry season river
flow declines.
The Himalayan glaciers feed the seven major
rivers of Asiathe
Ganges, Indus, Brahmaputra, Salween, Mekong, Yangtze, and Huang
He (Yellow)and
thus contribute to the year-round water supply of a vast population.
In India alone, some 500 million people, including those in New
Delhi and Calcutta, depend on glacier meltwater that feeds into
the Ganges River system. Glaciers in Central Asia's Tien Shan Mountains
have shrunk by nearly 30 percent between 1955 and 1990. In arid
western China, shrinking glaciers account for at least 10 percent
of freshwater supplies.
The largest aggregation of tropical glaciers
is in the northern Andes. The retreat of the Qori Kalis Glacier
on the west side of the Quelccaya Ice Cap that stretches across
Peru has accelerated to 155 meters a year between 1998 and 2000three
times faster than during the previous three-year period. The entire
ice cap could vanish over the next two decades.
The Antizana Glacier, which provides Quito,
Ecuador, with almost half its water, has retreated more than 90
meters over the last eight years. The Chacaltaya Glacier near La
Paz, Bolivia, melted to 7 percent of its 1940s volume by 1998. It
could disappear entirely by the end of this decade, depriving the
1.5 million people in La Paz and the nearby city of Alto of an important
source of water and power.
Africa's glaciers are also disappearing.
Across the continent, mountain glaciers have shrunk to one third
their size over the twentieth century. On Tanzania's Kilimanjaro,
ice cover has shrunk by more than 33 percent since 1989. By 2020
it could be completely gone.
In Western Europe, glacial area has shrunk
by up to 40 percent and glacial volume by more than half since 1850.
If temperatures continue to rise at recent rates, major sections
of glaciers covering the Alps and the French and Spanish Pyrenees
could be gone in the next few decades. During the record-high temperature
summer of 2003, some Swiss glaciers retreated by an unprecedented
150 meters. The United Nations Environment Programme is warning
that for this region long associated with ice and snow, warming
temperatures signify the demise of a popular ski industry, not to
mention a cultural identity.
Boundaries around Banff, Yoho, and Jasper
National Parks in the Canadian Rockies cannot stop the melting of
the glaciers there. Glacier National Park in Montana has lost over
two thirds of its glaciers since 1850. If temperatures continue
to rise, it may lose the remainder by 2030.
In just the past 30 years, the average temperature
in Alaska climbed more than 3 degrees Celsius (5 degrees Fahrenheit)easily
four times the global increase. Glaciers in all of Alaska's 11 glaciated
mountain ranges are shrinking. Since the mid-1990s, Alaskan glaciers
have been thinning by 1.8 meters a year, more than three times as
fast as during the preceding 40 years.
The global average temperature has climbed
by 0.6 degrees Celsius (1 degree Fahrenheit) in the past 25 years.
Over this time period, melting of sea ice and mountain glaciers
has increased dramatically. During this century, global temperature
may rise between 1.4 and 5.8 degrees Celsius, and melting will accelerate
further. Just how much will depend in part on the energy policy
choices made today.
Copyright
© 2004 Earth Policy Institute
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FOR ADDITIONAL INFORMATION
From Earth Policy Institute
Lester R. Brown, Plan
B: Rescuing a Planet Under Stress and a Civilization in Trouble
(New York: W.W. Norton & Company, 2003).
Lester R. Brown, Janet Larsen, and Bernie Fischlowitz-Roberts,
The
Earth Policy Reader (New York: W.W. Norton & Company, 2002).
Lester R. Brown, Eco-Economy:
Building an Economy for the Earth (New York: W.W. Norton
& Company, 2001).
Lester R. Brown, "Global Temperature Near Record
for 2002," Eco-Economy Update,
11 December 2002.
Lester R. Brown, "Earth's Ice Melting Faster than
Projected," Eco-Economy Update,
12 March 2002.
Lester R. Brown, "This Year May Be Second Warmest
on Record," Eco-Economy Update,
18 December 2001.
From Other Sources
Mark A.J. Curran, et al., "Ice Core Evidence for
Antarctic Sea Ice Decline Since the 1950s," Science, vol.
302 (14 November 2003), pp. 1203-06.
De Angelis and Skvarca, "Glacier Surge After Ice
Shelf Collapse," Science, vol. 299 (7 March 2003).
Mark B. Dyurgerov and Mark F. Meier, "Twentieth
Century Climate Change: Evidence from Small Glaciers," Proceedings
of the National Academy of Sciences, vol. 97, no. 4 (15 February
2000), 1406-11.
Goddard Institute for Space Studies, NASA Goddard
Space Flight Center Earth Sciences Directorate, "Global Temperature
Anomalies in .01 C," http:/www.giss.nasa.gov/data,
updated January 2001.
IPCC, Climate Change 2001: The Scientific Basis;
Impacts, Adaptation, and Vulnerability; and Mitigation. Contributions
of Working Group I, II, and III to the Third Assessment Report of
the Intergovernmental Panel on Climate Change (Cambridge and
New York: Cambridge University Press). Text and summaries of each
report available at http:/www.ipcc.ch.
W. Krabill et al., "Greenland Ice Sheet: High Elevation
Balance and Peripheral Thinning," Science, vol. 289 (21 July
2000), pp. 428-30.
Thomas V. Lowell, "As Climate Changes, So Do Glaciers,"
Proceedings of the National Academy of Sciences, vol. 97,
no. 4 (15 February 2000), 1351-54.
M.C. Serreze, et al., "A Record Minimum Arctic Sea
Ice Extent and Area in 2002," Geophysical Research Letters,
vol. 30, no. 3 (2003), pp. 1110-14.
Lars H. Smedsrud and Tore Furevik, "Towards an Ice-Free
Arctic?" Cicerone
2/2000.
Lonnie G. Thompson, et al., "Kilimanjaro Ice Core
Records: Evidence of Holocene Climate Change in Tropical Africa,"
Science, vol. 298 (18 October 2002), pp. 589-93
WWF, "Going,
Going, Gone!: Climate Change and Global Glacier Decline,"
news report, 27 November 2003.
LINKS
Global Land Ice Measurements from Space
http:/www.GLIMS.org
Institute of Arctic and Alpine Research, University
of Colorado
http:/instaar.colorado.edu
Intergovernmental Panel on Climate Change
http:/www.ipcc.ch
National Snow and Ice Data Center
http:/www-nsidc.colorado.edu
United Nations Framework Convention on Climate Change
http:/www.unfccc.de
World Glacier Inventory
http:/nsidc.org/data/glacier
_inventory/
World Glacier Monitoring Service
http:/www.geo.unizh.ch/wgms
Worldwatch Institute Climate Resource Center
http:/www.worldwatch.org
/topics/energy/climate
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