Did you know: For the first time in 2008 the world’s city dwellers outnumbered those in the countryside. The share of urbanites is projected to continue increasing, so that by 2030 some 60 percent of the world’s population will live in cities. For more information view the text and data in Chapter 6 of Plan B 4.0: Mobilizing to Save Civilization.
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 century—currently 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 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 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 percent—from 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 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 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 kilometers—three times the size of Texas—is 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.
Copyright © 2002 Earth Policy Institute