“[Brown’s] ability to make a complicated subject accessible to the general reader is remarkable...” –Katherine Salant, Washington Post
Chapter 4. Rising Temperatures and Rising Seas: Melting Ice and Rising Seas
In its landmark third edition report released in early 2001, the IPCC projected that sea level would rise during this century 0.09-0.88 meters (4-35 inches) as a result of thermal expansion and ice melting. New studies released during the two years since then indicate that the earth's ice cover is melting much faster than IPCC scientists assumed.23
A 2002 study by two scientists from the University of Colorado's Institute of Arctic and Alpine Research shows that the melting of large glaciers on the west coast of Alaska and in northern Canada is accelerating. Earlier data had indicated that the melting was raising sea level by 0.14 millimeters per year, but 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.24
The Colorado study is reinforced by a U.S. Geological Survey (USGS) study that 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 had dwindled from 150 in 1850 to fewer than 50 today. The remaining glaciers are projected to disappear within 30 years.25
Another team of USGS scientists, which used satellite data to measure changes in the area covered by glaciers worldwide, describes an accelerated melting of glaciers in several mountainous regions, including the South American Andes, the Swiss Alps, and the French and Spanish Pyrenees.26
The melting of glaciers is gaining momentum throughout the Andes. Lonnie Thompson of Ohio State University reports that the Qori Kalis glacier, which is located on the west side of the Quelccaya ice cap in the Peruvian Andes, shrank three times as fast each year from 1998 to 2000 as it did between 1995 and 1998. And the earlier rate, 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 Antisana glacier in Ecuador, which supplies half of the water for Quito, has retreated nearly 100 meters in the last eight years.27
Bernard Francou, research director for the French government's Institute of Research and Development, believes that within the next 15 years, 80 percent of South American glaciers will disappear. For countries like Bolivia, Peru, and Ecuador, which rely on glaciers for water for household and irrigation use, this is not good news.28
Lonnie Thompson's studies of Kilimanjaro show that between 1989 and 2000, Africa's tallest mountain lost 33 percent of its ice field. He projects that its snowcap could disappear entirely within the next 15 years.29
The vast snow/ice mass in the Himalayas is also retreating. Although data are not widely available, those glaciers that have been studied indicate an accelerating retreat. As one example, representatives of the major mountaineering association, The Union Internationale des Associations d'Alpinisme, report that the glacier that ended at the base camp from which Edmund Hillary and Tenzing Norgay launched their history-making ascent of Everest in 1953 has retreated about 5 kilometers (3 miles). Geologist Jeffrey Kargel, who studies the Himalayas, is not surprised by this. "That fits in with the general picture of what's happening in Nepal, India, Bhutan and, to a smaller extent, Tibet," he says.30
Both the North and the South Poles are showing the effects of rising temperature. While the South Pole is covered by a huge continent, the North Pole is covered by the Arctic Ocean. A flurry of papers presented at the annual conference of the American Geophysical Union (AGU) in December 2002 reported dramatic advances in ice melting. They noted that in summer 2002 the Arctic Ocean ice cover had shrunk to the smallest area seen since 1978, when detailed studies began. Mark Serreze of the National Snow and Ice Data Center in Boulder, Colorado, reported that this was the most abrupt change in the ocean's ice cover that scientists have seen during the 24 years they have been monitoring it.31
In addition to shrinking, the Arctic sea ice has thinned by 42 percent over the last 35 years—from an average of 3.1 meters to 1.8 meters. The combination of the shrinking and thinning has 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 within a matter of decades.32
If that happens, it would not affect sea level because the ice is already in the water. But it would alter the Arctic heat balance. When sunlight strikes ice and snow, roughly 80 percent of the light is reflected back into space and 20 percent is absorbed as heat. If, however, sunlight strikes land or open water, only 20 percent is bounced back into space and 80 percent is converted into heat, leading to higher temperatures. This is an example of a positive feedback loop, a situation in which a trend feeds on itself.33
The melting of Greenland's ice sheet is a different matter. Another report delivered at the AGU conference—this one by Konrad Steffen, a glaciologist at the University of Colorado—indicated that the ice cover on Greenland is also melting much faster over a 686,000-square-kilometer area (roughly a third of the total area) than at any time on record. Steffen described how he and his colleagues, who were camped on the normally frozen Greenland ice, were flooded under a foot of meltwater and had to be rescued by helicopter.34
The prospect of much warmer Arctic summers is of concern because Greenland, which is three times the size of Texas, lies partly within the Arctic Circle. An article in Science reports that if the entire ice sheet on this huge island were to melt, it would raise sea level 7 meters (23 feet). Such a melting, even under the most rapid warming scenario, would be measured in centuries, not years. Nonetheless, if the Greenland ice sheet does disappear, hundreds of coastal cities will be below sea level, as will the rice-growing river floodplains and deltas of Asia. Many island countries will cease to exist.35
At the other end of the earth, the Antarctic ice sheet, which covers a continent the size of the United States and is 2.6 kilometers (1.6 miles) thick on average, contains over 90 percent of the world's fresh water. The immediate concern here is not the ice that covers the continent but the ice shelves that extend from the continent into the surrounding seas, which are beginning to break up at an alarming pace.36
The ice shelves surrounding Antarctica are formed by the flow of glaciers from the continent to lower levels. This flow of ice, fed by the continuous formation of new ice on land and culminating in the breakup of the shelves on the outer fringe and the calving of icebergs, is not new. What is new is the pace of this process. When Larsen A, a huge ice shelf on the east coast of the Antarctic Peninsula, broke up in 1995, it was a signal that all was not well in Antarctica. In 2000, a huge iceberg nearly the size of Connecticut—11,000 square kilometers, or 4,250 square miles—broke off the Ross Ice Shelf.37
After Larsen A broke up, it was only a matter of time, given the rise in temperature in the region, before Larsen B would do the same. In November 2001, an alert went out to the scientific community from a researcher at the Instituto Antártico Argentino, who noted the unusually warm spring temperature and the 20-percent acceleration in the flow of the ice shelf. So when the northern part of the Larsen B ice shelf collapsed into the sea in March 2002, it did not come as a surprise. At about the same time, a huge chunk of ice broke off the Thwaite Glacier. Covering 5,500 square kilometers, this iceberg was the size of Rhode Island.38
Even veteran ice watchers are surprised at how quickly the disintegration is occurring. "The speed of it is staggering," said Dr. David Vaughan, a glaciologist at the British Antarctic Survey, which has been monitoring the Larsen Ice Shelf closely. Along the Antarctic Peninsula, in the vicinity of the Larsen ice shelf, the average temperature has risen 2.5 degrees Celsius over the last five decades. Higher temperatures lead to ice melting on the surface of the ice shelves. Scientists theorize that as the melted water on the surface penetrates fractures it weakens the ice, making it vulnerable to further fracturing.39
As the ice shelves, already in the water, break off from the continental ice mass, this does not affect sea level per se. What is of concern to scientists is that without the ice shelves to impede the flow of glacial ice, typically at a rate of 400-900 meters a year, the flow of ice from the continent could accelerate, leading to a thinning of the ice sheet on the edges of the Antarctic continent. If this were to happen, it would raise sea level. Dr. Neal Young of the Antarctic Cooperative Research Centre at the University of Tasmania in Australia notes that after Larsen A broke off, the upstream rate of glacial flow at least doubled.40
Experts now say it is getting harder to avoid the conclusion that there is a link between the buildup of greenhouse gases and the accelerating breakup of Antarctic ice shelves. As Dr. Theodore A. Scambos of the National Snow and Ice Data Center at the University of Colorado observes, "With the disappearance of ice shelves that have existed for thousands of years, you rather rapidly run out of other explanations."41
The accelerated melting of ice, which is consistent with the accelerating rise in temperature that has occurred since 1980, is of great concern in low-lying regions of coastal countries and low-lying island countries. In 2000 the World Bank published a map showing that a 1-meter rise in sea level would inundate half of Bangladesh's riceland. With a rise in sea level of up to 1 meter forecast for this century, tens of millions of Bangladeshis would be forced to migrate. In a country with 144 million people—already one of the most densely populated on earth—this would be a traumatic experience. Rice-growing river floodplains in other Asian countries would also be affected, including India, Thailand, Viet Nam, Indonesia, and China. With a 1-meter rise in sea level, more than a third of Shanghai would be under water. For China as a whole, 70 million people would be vulnerable to a 100-year storm surge.42
The most easily measured effect of rising sea level is the inundation of coastal areas. Donald F. Boesch, with the University of Maryland's Center for Environmental Sciences, estimates that for each 1-meter rise in sea level, the shoreline will retreat by an average 1,500 meters, or nearly a mile. With such a rise, the United States would lose 36,000 square kilometers (14,000 square miles) of land—with the middle Atlantic and Mississippi Gulf states losing the most. Large portions of Lower Manhattan and the Mall in the center of Washington, D.C., would be flooded with seawater during a 50-year storm surge. New Orleans would be under water.43
Thermal expansion of the oceans and ice melting are raising sea level at a measurable rate. It has become an indicator to watch—a trend that could force a human migration of unimaginable dimensions. It also raises questions about responsibility to other nations and to future generations that humanity has never before faced.
23. IPCC, op. cit. note 6.
24. University of Colorado at Boulder, "Global Sea Levels Likely to Rise Higher in 21st Century than Previous Predictions," press release (Boulder, CO: 16 February 2002).
25. "Alaska Examines Impacts of Global Warming," National Geographic News, 21 December 2001; Myrna H. P. Hall and Daniel B. Fagre, "Modeled Climate-Induced Glacier Change in Glacier National Park, 1850-2100," BioScience, February 2003, pp. 131-40.
26. American Institute of Physics, "New Research Shows Mountain Glaciers Shrinking Worldwide," press release (Boston: 30 May 2001).
27. Lonnie G. Thompson, "Disappearing Glaciers Evidence of a Rapidly Changing Earth," American Association for the Advancement of Science annual meeting proceedings, San Francisco, CA February 2001; Eric Hansen, "Hot Peaks," On Earth, fall 2002, p. 8.
28. Hansen, op. cit. note 27.
29. Thompson, op. cit. note 27.
30. Kargel quoted in Hansen, op. cit. note 27.
31. David Perlman, "Global Warming Evidence Mounts: Flurry of Reports Show a Withering Ice Cap," San Francisco Chronicle, 23 December 2002; M. C. Serreze et al., "A Record Minimum Arctic Sea Ice Extent and Area in 2002," Geophysical Research Letters, vol. 30, no. 3, p. 1110.
32. D. A. Rothrock et al., "Thinning of the Arctic Sea-Ice Cover," Geophysical Research Letters, 1 December 1999, pp. 3469-72; Lars H. Smedsrud and Tore Furevik, "Towards an Ice-Free Arctic?" Cicerone, no. 2, 2000.
33. Richard A. Kerr, "Will the Arctic Ocean Lose All Its Ice?" Science, 3 December 1999, p. 1828.
34. Perlman, op. cit. note 31.
35. W. Krabill et al., "Greenland Ice Sheet: High Elevation Balance and Peripheral Thinning," Science, 21 July 2000, p. 428.
36. National Science Foundation, Office of Polar Programs, "Ice Sheets," at www.nsf.gov/od/opp/support/icesheet.htm, updated March 2001.
37. National Snow and Ice Data Center, "Antarctic Ice Shelf Collapses," at nsidc.org/iceshelves/larsenb2002, 19 March 2002; "Breakaway Bergs Disrupt Antarctic Ecosystem,"Environment News Service, 9 May 2002; "Giant Antarctic Ice Shelves Shatter and Break Away," Environment News Service, 19 March 2002.
38. National Snow and Ice Data Center, op. cit. note 37; "Breakaway Bergs Disrupt Antarctic Ecosystem," op. cit. note 37; "Giant Antarctic Ice Shelves Shatter and Break Away," op. cit. note 37.
39. National Snow and Ice Data Center, op. cit. note 37; "Breakaway Bergs Disrupt Antarctic Ecosystem," op. cit. note 37; "Giant Antarctic Ice Shelves Shatter and Break Away," op. cit. note 37; Vaughan quoted in Andrew Revkin, "Large Ice Shelf in Antarctica Disintegrates at Great Speed," New York Times, 20 March 2002.
40. Michael Byrnes, "New Antarctic Iceberg Split No Threat," Reuters, 20 May 2002; Young quoted in "Giant Antarctic Ice Shelves Shatter and Break Away," op. cit. note 37.
41. Scambos quoted in Revkin, op. cit. note 39.
42. World Bank, World Development Report 1999/2000 (New York: Oxford University Press, 2000), p. 100; population from United Nations, World Population Prospects: The 2002 Revision (New York: February 2003); Shanghai and China as a whole from Stuart R. Gaffin, High Water Blues: Impacts of Sea Level Rise on Selected Coasts and Islands (Washington, DC: Environmental Defense Fund, 1997), p. 27.
43. Boesch cited in Bette Hileman, "Consequences of Climate Change," Chemical & Engineering News, 27 March 2000, pp. 18-19; James E. Neumann et al., Sea-level Rise & Global Climate Change: A Review of Impacts to U.S. Coasts (Arlington, VA: Pew Center on Global Climate Change, 2000); Gaffin, op. cit. note 42.
Copyright © 2003 Earth Policy Institute