EARTH'S ICE MELTING
FASTER THAN PROJECTED
EARTH'S ICE MELTING
FASTER THAN PROJECTED
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, willneed to revise upward its projected rise in sea level for thiscentury--currently estimated to range from 0.09 meters to 0.88 meters (from4 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 thewest coast of Alaska and in northern Canada is accelerating. Earlier data indicated that the melting of glaciers in these areas was raising sea levelby 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 1850to fewer than 50 today. They project the remaining glaciers will disappearwithin 30 years.
Another team of USGS scientists, which uses satellite data to measurechanges in the area covered by glaciers, describes an accelerated melting ofglaciers 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 Quri Kalis glacier,which is located on the west side of the Quelccaya ice cap in the PeruvianAndes, the annual shrinkage from 1998 to 2000 was three times that which occurred between 1995 and 1998. And that, in turn, was nearly double theannual rate of retreat from 1993 to 1995. Thompson also projects that thelarge Quelccaya ice cap will disappear entirely between 2010 and 2020.
The vast snow/ice mass in the Himalayas, which ranks third in fresh waterstored, after Antarctica and Greenland, is also retreating. Although dataare not widely available for the Himalayan glaciers, those that have been studied indicate an accelerating retreat. For example, data for the 1990sshow that the Dokriani Bamak Glacier in the Indian Himalayas retreated by 20meters 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.
Both the North and the South Poles are showing the effects of climatechange. 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 shelves--the portions of the ice sheet that extend into the surrounding seas--are 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 fullretreat. 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 havebroken 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 iscovered by the Arctic Ocean. Arctic sea ice is melting fast. Over the last35 years, the ice has thinned 42 percent--from an average of 3.1 meters to1.8 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 passage--a shortcut from Europe to Asia--could 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 sealevel because the ice is already in the water, but it would alter theregional 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 apositive feedback loop, a situation where a trend creates conditions that reinforce itself.
Richard Kerr, writing in Science, says summer "would convert the ArcticOcean from a brilliantly white reflector sending 80 percent of solar energyback into space into a heat collector absorbing 80 percent of [incomingsunlight]." The discovery of open water at the North Pole by an ice breaker cruise ship in August 2000 provides further evidence that the meltingprocess 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 withinthe Arctic Circle. In a Science article in 2000, a team of U.S. scientistsfrom 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 south eastern coasts. This huge island of 2.2 million squarekilometers--three times the size of Texas--is experiencing a net loss of 51billion cubic meters of ice each year, which is raising sea level by 0.13millimeters 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 morethan a meter a year since 1993. If all the ice on Greenland were to melt, itwould raise sea level by 7 meters (23 feet), but even under a hightemperature rise scenario, it could take many centuries for it to meltcompletely.
The accelerated melting of ice, particularly during the last decade or so,is consistent with the accelerating rise in temperature that has occurredsince 1980. With the IPCC projecting global average temperature to rise by1.4 to 5.8 degrees Celsius (2.5 to 10.4 degrees Fahrenheit) during thiscentury, the melting of ice will likely continue to gain momentum.
Our generation is the first to have the capacity to alter the earth'sclimate. We are also, therefore, the first to wrestle with the ethical question of whether the capacity to change the planet's climate gives us theright to do so.
Written by: Lester R. Brown, Earth Policy Institute
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