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Four years ago the Intergovernmental Panel on Climate Change (IPCC) concluded that humans are at least partly responsible for global warming: "The balance of evidence suggests a discernible human influence on global climate," IPCC said.[1] IPCC is an international group of 2500 meteorologists gathered under the auspices of the United Nations, trying to figure out why the Earth is warming up and what it might mean for human civilization.

The mechanism of warming is called the "greenhouse effect." Sunlight streams in from outer space, strikes the surface of the planet, turns to heat and then is radiated back out toward outer space. But some of the heat cannot escape because it is reflected back to Earth by "greenhouse gases" in the atmosphere. These "greenhouse gases" (water vapor, carbon dioxide and methane) allow sunlight to pass through but they block heat, thus acting like the glass roof on a greenhouse, producing warmth within.

The greenhouse effect is natural -- without it the Earth would be a frozen rock spinning through space. But over the past few hundred years, humans have contributed substantially to an increase in greenhouse gases. Burning coal, oil and natural gas (so-called fossil fuels), plus deforestation, have increased the atmospheric content of carbon dioxide by 31% (from 275 parts per million [ppm] to 360 ppm) during the past few hundred years, a trend that continues today. Fossil fuel combustion and deforestation now add about 7.7 billion tons (7 billion metric tonnes) of carbon dioxide to the atmosphere each year. Other human activities have increased the methane content of the atmosphere -- growing cattle, growing rice, and landfilling garbage.

Since 1995, much new evidence has come to light indicating that the Earth is indeed warming and that human activities are at least partly responsible. A recent summary article by Bette Hileman in CHEMICAL & ENGINEERING NEWS, voice of the American Chemical Society, describes some of the new evidence indicating that the planet is warming at an accelerating pace:

** The Earth's average temperature has been rising for at least 100 years, but in recent decades the rate of increase has speeded up. Eleven of the past 16 years have been the hottest of the century. The average global temperature in 1998 was higher than it had been at any other time during the previous 1000 years.

** The polar regions of the planet are heating up much more rapidly than the average. Alaska is now as much as 10 degrees Fahrenheit (F.) (6 degrees Celsius [C.]) warmer than it was 35 years ago. As the frozen north warms and thaws, peat buried in the tundra decays, releasing carbon dioxide. This is a positive feedback mechanism that could speed up the rate of increase of greenhouse gases in the atmosphere -- the warmer the tundra becomes, the more carbon dioxide it releases, in turn warming the tundra further. According to Walter C. Oechel, director of the Global Change Research Group at San Diego State University (California), the arctic tundra has been a sink (or storage place) for carbon for the last 9000 years, but since 1982 its role has reversed and now it has become a source of carbon to the atmosphere.

Some far-northern (boreal) forests also seem to be shifting their role from that of a carbon sink to a carbon source for the atmosphere as warmer temperatures thaw frozen soils.[2] Whether the entire boreal forest belt, which encircles the Earth, has become a net source of carbon remains unknown.

Bette Hileman does not say so, but the warming arctic tundra will likely also release methane gas which, pound for pound, is about 20 times as powerful as carbon dioxide at creating a greenhouse effect.[3] The quantity of carbon locked in arctic soils is huge and the positive feedback loop that has begun to release it to the atmosphere is ominous.

** Average summertime temperatures in Antarctica have risen 4.5 degrees F. (2.5 degrees C.) since the 1940s. According to members of the British Antarctic Survey, ice shelves along the coast of the Antarctic Peninsula have been breaking up for 50 years, having lost 7000 square kilometers (2703 square miles) during that time. The loss of 3000 square kilometers (1158 square miles) within just the last year indicates that the breakup of ice shelves has accelerated.

The Greenland Ice Sheet, the world's second largest glacier, is growing thinner at the rate of a meter (39 inches) per year. However, snowfall may be increasing in polar regions, so no one is yet sure whether the overall amount of ice at the poles is changing.

** The bleaching and loss of corals in the world's warm oceans (Indo-Pacific, western Atlantic, and Caribbean) provide further evidence of accelerated global warming. Corals are showing signs of stress in areas of human habitation and in uninhabited regions. In uninhabited regions, the main causes are likely to be increased ultraviolet light penetrating through the Earth's damaged ozone shield, and global warming. Coral bleaching occurs when water temperatures rise, and coral bleaching has been increasing worldwide since the 1970s as Earth's temperature has risen most steeply.

Furthermore, recent work shows that, as the carbon dioxide content of the atmosphere increases, so does the carbon dioxide content of ocean water. This in turn lowers the concentration of carbonate ion, reducing the ability of corals to build their skeletons.[4] The future for coral reefs looks grim.

Coral reefs are economically important -- they provide food, coastal protection, and new medications for drug-resistant diseases. And they attract tourists by the millions: Caribbean countries derive half their income from coral reefs. The coral reefs of southeast Asia provide homes for one-quarter of the world's fish species.

** Annual precipitation over the continental U.S. has increased about 10% during this century, much of it during the winter, and much of it in heavy events. For example, the number of days with rainfall exceeding 2 inches has increased about 10% during the past century. Similar trends are observable in Canada, Japan, Russia, China, and Australia.

Other consequences of global warming include:

** Moisture in the lower atmosphere has increased about 10% during the past 20 years.

** The annual number of intense storms over the North Atlantic and the North Pacific has doubled since 1900.

** There have been more, and longer-lasting, El Nino events since the 1970s. El Nino is a huge but localized warming in the eastern Pacific Ocean that gives rise to violent storms along the U.S. Pacific coast, devastating droughts in Africa and Australia, and often a failure of the monsoon rains in Asia.

** New computer models have been able to mimic past climate changes, and they predict future warming of the atmosphere. Skeptics used to say that computer models had done such a poor job of mimicking past events that their predictive ability must also be flawed. That argument has been put to rest by better models that track past events properly and which now predict an average global temperature rise somewhere between 1.2 degrees C. (2.2 degrees F.) and 4 degrees C. (7.2 degrees F.) in the next century. Even a 1 degree C. (1.8 deg. F.) average temperature rise could have important consequences because of exaggerated effects already evident at the poles, though not all scientists agree with this assessment.

** Rather than diminish production of carbon dioxide, the U.S. government favors a technical fix: U.S. global warming policy relies on the ability of forests and agricultural soils to sop up excess carbon dioxide from the atmosphere. A 1998 paper by U.S. government scientists seemed to show that North American forests and soils were absorbing all of the carbon dioxide being emitted by the burning of fossil fuels in North America.[5] Based on that study, the U.S. demanded that forests-as-carbon -sinks be written into the Kyoto Treaty, an international agreement intended to slow the production of greenhouse gases. (See REHW #577.) At the meeting in Kyoto (Japan), the European Union remained skeptical of the U.S. approach, but the U.S. threatened to walk out if its approach was rejected. Now, according to Bette Hileman, two additional studies -- one from France and the other from Australia -- have challenged the findings of the original U.S. study, but these new studies remain unpublished and therefore outside the debate.

This issue of forests as "sinks" for excess carbon has paralyzed Kyoto Treaty negotiations since the Kyoto meeting because the issue is not fully resolvable with present-day science and the U.S. continues to insist that its viewpoint is defensible. Paralysis suits many U.S. leaders just fine -- key members of Congress have indicated that the Kyoto Treaty will be ratified over their dead bodies because they say the Kyoto Treaty will harm the U.S. economy. But what if global warming will harm the economy for our children in the future? Let the unborn speak now or forever hold their peace.

Independent U.S. scientists who have examined the ability of forests to absorb carbon dioxide are not optimistic that the U.S. "sinks" plan has much merit. Under ideal conditions, forests may be able to absorb as much as 50% of excess carbon dioxide from the atmosphere, but to achieve that level of absorption would require all trees to be young and all trees to be as responsive to carbon dioxide as the most responsive, the loblolly pine. And of course when the trees die, they will release the excess carbon back into the ecosystem. To prevent global warming, trees would have to keep excess carbon out of the atmosphere forever.

Cleaner sources of energy are already available and affordable. Adopting them in the U.S. alone would create 770,000 jobs, save $530 per household per year, and significantly reduce the threat of global warming.[6] Why can't we make the shift? A recent report from the Natural Resources Defense Council (NRDC), U.S. Public Interest Research Group, and the Union of Concerned Scientists points out that 80% of greenhouse gases are produced by only 122 corporations,[7] which act as "carbon pushers" comparable to drug pushers. The authors of the report do not express it quite this way, but the conclusion is obvious: these 122 corporations are jeopardizing the integrity of the entire global ecosystem, endangering the future for all children, and holding the world's people and their governments hostage by a combination of bribery and brute force. A simple question: Why do we allow such antisocial -- even sociopathic -- behavior to go unrewarded by prison sentences for culpable executives and boards of directors? Please give it some thought.

--Peter Montague (National Writers Union, UAW Local 1981/AFL-CIO)


[1] Bette Hileman, "Case Grows for Climate Change," C&EN [CHEMICAL & ENGINEERING NEWS] (August 9, 1999), pgs. 16-23.

[2] M. L. Goulden and others, "Sensitivity of Boreal Forest Carbon Balance to Soil Thaw," SCIENCE Vol. 279 (January 9, 1998), pgs. 214-216.

[3] Jeff Hecht, "Shallow Methane Could Turn on the Heat," NEW SCIENTIST (July 8, 1995), pg. 16. And: Jeff Hecht, "Baked Alaska," NEW SCIENTIST (October 11, 1997), pg. 4. And: Fred Pearce, "Methane: The Hidden Greenhouse Gas. Coming out of cattle, rubbish tips and rice fields, is warming the earth. Yet methane from the Arctic could be the most damaging of all," NEW SCIENTIST (May 6, 1989), pg. 37.

[4] Joan A. Kleypas and others, "Geochemical Consequences of Increased Atmospheric Carbon Dioxide on Coral Reefs," SCIENCE Vol. 284 (April 2, 1999), pgs. 118-120.

[5] S. Fan and others, "A Large Terrestrial Carbon Sink in North America Implied by Atmospheric and Oceanic Carbon Dioxide Data and Models," SCIENCE Vol. 282 (October 16, 1998), pgs. 442-446.

[6] ENERGY INNOVATIONS: A PROSPEROUS PATH TO A CLEAN ENVIRONMENT (Washington, D.C.: American Council for an Energy-Efficient Economy [1001 Connecticut Ave., NW, Suite 801, Washington, D.C. 20036; phone (202) 429-0063], June 1997. Available for $25. See http://www.tellus.org/ei/eireport.html.

[7] KINGPINS OF CARBON; HOW FOSSIL FUEL PRODUCERS CONTRIBUTE TO GLOBAL WARMING (New York: Natural Resources Defense Council and others, July 1999). Tel. (212) 727-1773. Available at: http:- file://www.nrdc.org/nrdcpro/fppubl.html .

Descriptor terms: global warming; greenhouse effect; fossil fuel; coral; precipitation increases; tundra; forests; carbon sinks; carbon sources; methane gas; glaciers;

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