March 12, 2002-4
Copyright © 2002 Earth Policy Institute
Earth's Ice Melting Faster Than Projected
Lester R. Brown
Several new studies report that the earth's ice cover is melting
faster than projected by the Intergovernmental Panel on Climate
Change (IPCC) in its landmark report released in early 2001. Among
other things, this means that the IPCC team, which did not have
the ice melt data through the 1990s, will need to revise upward
its projected rise in sea level for this centurycurrently
estimated to range from 0.09 meters to 0.88 meters (from 4 to 35
inches).
A study by two scientists from the University of Colorado's Institute
of Arctic and Alpine Research shows that melting of the large glaciers
on the west coast of Alaska and in northern Canada is accelerating.
Earlier data indicated that the melting of glaciers in these areas
was raising sea level by 0.14 millimeters per year, but the new
data for the 1990s indicate that the more rapid melting is now raising
sea level by 0.32 millimeters a year, more than twice as fast.
The Colorado study is reinforced by a U.S. Geological Survey (USGS)
study, which indicates glaciers are now shrinking in all 11 of Alaska's
glaciated mountain ranges. An earlier USGS study reported that the
number of glaciers in Glacier National Park in the United States
has dwindled from 150 in 1850 to fewer than 50 today. They project
the remaining glaciers will disappear within 30 years.
Another team of USGS scientists, which uses satellite data to measure
changes in the area covered by glaciers, describes an accelerated
melting of glaciers in several mountainous regions, including the
South American Andes, the Swiss Alps, and the French and Spanish
Pyrenees.
Glaciers are shrinking faster throughout the Andes. Professor Lonnie
Thompson of Ohio State University reports that for the Qori Kalis
glacier, which is located on the west side of the Quelccaya ice
cap in the Peruvian Andes, the annual shrinkage from 1998 to 2000
was three times that which occurred between 1995 and 1998. And that,
in turn, was nearly double the annual rate of retreat from 1993
to 1995. Thompson also projects that the large Quelccaya ice cap
will disappear entirely between 2010 and 2020.
The vast snow/ice mass in the Himalayas, which ranks third in fresh
water stored, after Antarctica and Greenland, is also retreating.
Although data are not widely available for the Himalayan glaciers,
those that have been studied indicate an accelerating retreat. For
example, data for the 1990s show that the Dokriani Bamak Glacier
in the Indian Himalayas retreated by 20 meters in 1998, more than
during the preceding five years.
Thompson has also studied Kilimanjaro, observing that between 1989
and 2000, Kilimanjaro lost 33 percent of its ice field. He projects
that it could disappear entirely within the next 15 years. (See
table.)
Both the North and the South Poles are showing the effects of climate
change. The South Pole is covered by a continent the size of the
United States. The Antarctic ice sheet, which is 1.5 miles thick
in some places, contains over 90 percent of the world's fresh water.
While this vast ice sheet is relatively stable, the ice shelvesthe
portions of the ice sheet that extend into the surrounding seasare
fast disappearing. A team of U.S. and British scientists reported
in 1999 that the ice shelves on either side of the Antarctic Peninsula
are in full retreat. From mid-century through 1997, these areas
lost 7,000 square kilometers as the ice sheet disintegrated. But
then within scarcely one year they lost another 3,000 square kilometers.
Delaware-sized icebergs that have broken off are a threat to ships
in the area. The scientists attribute the accelerated ice melting
to a regional temperature rise of 2.5 degrees Celsius (4.5 degrees
Fahrenheit) since 1940.
While the South Pole is covered by a huge continent, the North Pole
is covered by the Arctic Ocean. Arctic sea ice is melting fast.
Over the last 35 years, the ice has thinned 42 percentfrom
an average of 3.1 meters to 1.8 meters. It has also shrunk by 6
percent since 1978. Together, thinning and shrinking have reduced
the mass of sea ice by half. A team of Norwegian scientists projects
that the Arctic Sea could be entirely ice-free during the summer
by mid-century, if not before.
If this melting materializes as projected, the early explorers'
dream of a northwest passagea shortcut from Europe to Asiacould
be realized. Unfortunately, what was a dream for them could be a
nightmare for us.
If the Arctic Ocean becomes ice-free in the summer, it would not
affect sea level because the ice is already in the water, but it
would alter the regional heat balance. When sunlight strikes ice
and snow, most of it is reflected back into space, but if it instead
strikes land or open water, then much of the energy in the light
is absorbed and converted into heat, leading to higher temperatures.
This is what computer modelers refer to as a positive feedback loop,
a situation where a trend creates conditions that reinforce itself.
Richard Kerr, writing in Science, says summer "would convert the
Arctic Ocean from a brilliantly white reflector sending 80 percent
of solar energy back into space into a heat collector absorbing
80 percent of [incoming sunlight]." The discovery of open water
at the North Pole by an ice breaker cruise ship in August 2000 provides
further evidence that the melting process may now be feeding on
itself.
This prospect of much warmer summers in the Arctic is of concern
because Greenland, which has the world's second largest ice sheet,
is largely within the Arctic Circle. In a Science article in 2000,
a team of U.S. scientists from NASA reported that the vast Greenland
ice sheet is starting to melt. Greenland is gaining some ice in
higher elevations in its northern reaches, but it is losing much
more at the lower elevations along its southern and southeastern
coasts. This huge island of 2.2 million square kilometersthree
times the size of Texasis experiencing a net loss of 51 billion
cubic meters of ice each year, which is raising sea level by 0.13
millimeters per year, according to the NASA team.
The team also reports that the melting there appears to be accelerating
because the ice sheet on its southern and eastern edges has thinned
by more than a meter a year since 1993. If all the ice on Greenland
were to melt, it would raise sea level by 7 meters (23 feet), but
even under a high temperature rise scenario, it could take many
centuries for it to melt completely.
The accelerated melting of ice, particularly during the last decade
or so, is consistent with the accelerating rise in temperature that
has occurred since 1980. With the IPCC projecting global average
temperature to rise by 1.4 to 5.8 degrees Celsius (2.5 to 10.4 degrees
Fahrenheit) during this century, the melting of ice will likely
continue to gain momentum.
Our generation is the first to have the capacity to alter the earth's
climate. We are also, therefore, the first to wrestle with the ethical
question of whether the capacity to change the planet's climate
gives us the right to do so.
See
data and graphs
Copyright
© 2002 Earth Policy Institute
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FOR ADDITIONAL INFORMATION
From Earth Policy Institute
Lester R. Brown, Eco-Economy:
Building an Economy for the Earth (New York: W.W. Norton
& Company, 2001).
Lester R. Brown, "This Year May Be Second Warmest
on Record," Eco-Economy Update,
18 December 2001.
From Worldwatch Institute
Seth Dunn, Global Temperature Steady
and Carbon Emissions Continue Decline, in Worldwatch
Institute, Vital Signs 2001: The Trends that are Shaping Our
Future (New York: W.W. Norton & Company, 2001), pp. 50-53.
From Other Sources
Dorthe Dahl-Jensen, "The Greenland Ice Sheet Reacts,"
Science, 21 July 2000.
Goddard Institute for Space Studies, NASA Goddard
Space Flight Center Earth Sciences Directorate, Global Temperature
Anomalies in .01 C, updated January 2002, http:/www.giss.nasa.gov/data.
IPCC, Climate Change 2001. Contributions of Working
Groups 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 available at http:/www.ipcc.ch.
C.D. Keeling, T.P. Whorf, and the Carbon Dioxide
Research Group, Atmospheric Carbon Dioxide Record from Mauna
Loa, Scripps Institution of Oceanography, University of California,
13 August 2001, http:/cdiac.esd.ornl.gov/ftp/
ndp001/maunaloa.co2.
Richard Kerr, Will the Arctic Lose All Its
Ice? Science, v. 286, 3 December 1999, p. 1828.
W. Krabill et al., Greenland Ice Sheet: High-Elevation
Balance and Peripheral Thinning, Science, 21 July 2000.
D.A. Rothrock et al., Thinning of the Arctic
Sea-Ice Cover, Geophysical Research Letters, v. 26,
n. 23, 1 December 1999, pp. 3469-3472.
Lars H. Smedsrud and Tore Furevik, Towards
an Ice-Free Arctic? Cicerone, 2/2000, http:/www.cicero.uio.no/cicerone
/00/2/en/smedsrud.pdf
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
International Research Institute for Climate Prediction
http:/iri.ldeo.columbia.edu/
climate/cid/
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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