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. 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
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
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
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. 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. 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
** 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. 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. 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. 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, 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)
 Bette Hileman, "Case Grows for Climate Change," C&EN
[CHEMICAL & ENGINEERING NEWS] (August 9, 1999), pgs. 16-23.
 M. L. Goulden and others, "Sensitivity of Boreal Forest
Carbon Balance to Soil Thaw," SCIENCE Vol. 279 (January 9, 1998),
 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.
 Joan A. Kleypas and others, "Geochemical Consequences of
Increased Atmospheric Carbon Dioxide on Coral Reefs," SCIENCE
Vol. 284 (April 2, 1999), pgs. 118-120.
 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.
 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
 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:-
Descriptor terms: global warming; greenhouse effect; fossil fuel;
coral; precipitation increases; tundra; forests; carbon sinks;
carbon sources; methane gas; glaciers;