A new study  makes it clear that global warming will be the greatest
challenge that humans have ever faced.
Global warming is caused by the "greenhouse effect," which in turn is
caused by a buildup of carbon dioxide (CO2) and other gases in the
Earth's atmosphere. These gases act like the glass covering a
greenhouse; they let sunlight in but they don't let it back out again.
The result is a buildup of heat inside the greenhouse, which in the
case of a real greenhouse is good. However in this instance the
"greenhouse" is planet Earth, and warming up the planet will cause big
trouble. "A continuous warming will cause extraordinary disruption of
the human enterprise," says biologist George M. Woodwell, director of
the Woods Hole Research Center in Massachusetts.
The "greenhouse effect" itself is normal and natural. Carbon dioxide
and water vapor ordinarily trap some of the heat from sunlight, keeping
the Earth about 60 degrees Fahrenheit (F) warmer than it would
otherwise be, thus making life possible. Before the industrial age
began, in about 1750, the atmosphere contained 275 parts per million
(ppm) of carbon dioxide (CO2).
In the Earth's distant past, the amount of CO2 in the atmosphere has
varied up and down; and the planet's temperature has varied up and down
in lock step with the CO2. See Figure 1, which was produced by
scientists who found the history of earth's climate and atmosphere
revealed in the polar ice caps. There is little doubt that as CO2 has
gone up in the past, Earth's temperature has gone up. Thus the
"greenhouse effect" is not doubted by physicists, who know that CO2
really does trap heat from the sun. But there is a mystery in our
Humans have recently been loading up the atmosphere with CO2 and other
so-called "greenhouse gases," yet the planet's temperature has not
risen as high as the theory predicts it should. When scientists look at
the amount of greenhouse gases, and then check the planet's
temperature, they don't find as much warming as the CO2 would lead them
to expect. This is why we hear, "Oh, global warming isn't really a
problem, it isn't really happening."
The planet IS warming. Since 1880, when careful temperature records
began to be kept in the U.S., the average temperature has risen about 1
degree Fahrenheit. But if greenhouse gases really had the effect that
scientists say they do, the temperature should have risen by 2 degrees
F or more by now. This discrepancy between what scientists SAY should
be happening, and what IS happening, provides wiggle room for those who
want to deny the existence of the problem entirely. IT WILL ALLOW THE
DEBATE OVER GREENHOUSE WARMING TO CONTINUE FOR DECADES, WHILE THE
BUILDUP OF GREENHOUSE GASES INEXORABLY CONTINUES.
Recent findings have now explained the mystery. Although a buildup
of greenhouse gases is occurring (and is in fact accelerating), three
other forces are working simultaneously to cool the planet off. These
cooling forces are "masking" or canceling out the warming effects of
the greenhouse gases.
There are four kinds of greenhouse gases: CO2, methane, nitrous oxide,
and CFCs or chlorofluorocarbons. The main culprit is CO2, and the
greenhouse potential of the other gases is often expressed as "CO2
equivalents." When the warming effect of all four gases is added
together today and translated into CO2 equivalents, we have 425 ppm of
CO2 equivalents in the atmosphere, a 55% increase since 1750. (Actual
CO2 is now 356 ppm and the remainder is other greenhouse gases.)
CO2 itself comes chiefly from the combustion of coal and oil. Methane
comes from agriculture (mainly the growing of rice and cattle). Sources
of nitrous oxide are not well understood but production of Nylon is
certainly one source, and catalytic converters on automobiles, and
nitrogen fertilizers may be others. CFCs are created exclusively by
humans; they are refrigerants that are now famous because they are
destroying the Earth's stratospheric ozone layer, allowing an increase
in deadly ultraviolet light to reach the Earth's surface (see RHWN
Ironically the heating effect of these four greenhouse gases is being
nearly canceled out by other pollutants.
First, the effects of the CFCs are being countered by the CFCs
themselves as they destroy the stratospheric ozone layer. Ozone itself
is a greenhouse gas. The CFCs contribute to the greenhouse effect
themselves, but they destroy the ozone, thus removing the ozone's
greenhouse effect. Thus CFCs cancel out their own warming effect.
However, as CFCs are being phased out, DuPont and others are phasing in
substitute gases which are, themselves, powerful greenhouse gases, but
which will not destroy the ozone layer as effectively as the CFCs. The
effect of the new CFC substitutes will be to promote global warming.
Secondly, the injection of sulfur into the atmosphere in the form of
tiny particles emitted from the tall smoke stacks of coal-burning power
plants (and from metal smelters, and to a lesser extent from
automobiles), has created a haze over the whole planet, which is
reflecting sunlight back out into space. As a result, less sunlight is
striking the Earth's surface. This has nearly canceled out the warming
effects of all the greenhouse gases.
As sulfur pollution becomes better-controlled (for example, by
provisions of the Clean Air Act of 1990), the sulfur haze will clear up
and will "unmask" the effects of the greenhouse gases which are
relentlessly building up. At this point--in a decade or two--global
warming will become apparent with a vengeance.
The third (temporary) masking effect is the eruption of Mount Pinatubo
in June, 1990. Airborne debris from Pinatubo has reduced the sunlight
reaching Earth's surface about one percent and produced the relatively
cool summer that we all experienced in 1992.
Pinatubo's cooling effects will disappear after a year or two. But the
masking effects of CFCs and sulfur will linger for a decade or longer.
While this masking is occurring, those who are inclined to pooh-pooh
the problem, such as most political leaders in recent memory, will be
able to pretend the problem isn't real and will prevent the action we
need: a rapid transition away from our coal-and-oil-based economy and a
switch to renewable fuels. Meanwhile greenhouse gases are inexorably
building. CO2 alone grows at 1.5 ppm each year.
When the effects of greenhouse gases become fully apparent, what will
happen? Ultimately, major shifts in ecosystems will occur. Cold regions
will become warmer; warm regions will become hotter. Rainfall patterns
will change. The interiors of continents, such as the corn-and wheat-
growing regions of the U.S. may become drier and less productive.
In the meantime we can probably expect unstable weather conditions,
such as more unusual events like big hurricanes, tornadoes, droughts,
floods, and extremes of temperature (hot AND cold). As Douglas Cogan
A SIMPLE ANALOGY TO THE PRESENT SITUATION IS TRYING TO PREDICT WHEN
WATER WILL DRIP FROM A FAUCET. WHEN THE FLOW OF WATER THROUGH THE SPOUT
IS SLOW AND REGULAR, ONE CAN OBSERVE THE PATTERN OF DROPS AND EASILY
PREDICT WHEN THE NEXT DROP WILL FALL IF THE FLOW IS THEN INCREASED
SUFFICIENTLY AND MAINTAINED AT THAT RATE, ONE CAN SIMILARLY FORECAST
THAT THE DRIPS WILL BEAD TOGETHER AND FORM A CONTINUOUS STREAM. THE
SYSTEM HAS SHIFTED FROM ONE STEADY STATE TO ANOTHER. BUT IF THE FLOW OF
WATER IS INCREASED GRADUALLY, THERE WILL BE A PERIOD WHEN THE DRIPS
COME TWO OR THREE IN A ROW, THAT PAUSE FOR AN INSTANT, FOLLOWED BY FIVE
DRIPS IN RAPID SUCCESSION, AND SO ON; THE PATTERN BECOMES ERRATIC AND
HIGH UNPREDICTABLE. THIS UNSTEADY PHASE IS THE PART OF GLOBAL WARMING
THAT THE PLANET MAY NOW BE EXPERIENCING, AS THE FLOW OF GREENHOUSE
GASES ENTERING THE ATMOSPHERE SLOWLY INCREASES. [pgs. 42-43]
Outstanding among all the available facts is the global temperature
record dating back more than a century, in which the 1980s stand out as
the warmest decade by far, and in which the '90s are now setting new
The ten warmest years since 1880 have been (in temperature order):
1990; 1991; 1988 and 1981 (tied); 1987; 1983 and 1980 (tied); 1989;
1973; 1986 and 1977 (tied). Is it a coincidence that the past six years
are among the 10 hottest years ever recorded? Not likely.
[Diagram has been removed. Fig. 1 Long-term Variations in Global
Temperature and Atmospheric Carbon Dioxide. Notice how one tracks the
other It seems highly unlikely that future patterns will be different.
Source: J.M. Barnola, et al. "Wostok Ice Core Provides 160,000-year
Record of Atmospheric CO2," NATURE, Vol. 329, No. 6138 (1-7 October
1987), p. 410.]
 Douglas Cogan, THE GREENHOUSE GAMBIT: BUSINESS AND INVESTMENT
RESPONSES TO CLIMATE CHANGE (Washington, DC: Investor Responsibility
Research Center [IRRC], 1992). Available for $45 from IRRC, 1755
Massachusetts Avenue, N.W., Washington, DC 20036; phone (202) 234-7500.
 THE EARTH IN TRANSITION; PATTERNS AND PROCESSES OF BIOTIC
IMPOVERISHMENT (NY: Cambridge University Press, 1990), pg. 5.
 Intergovernmental Panel on Climate Change [IPCC], 1992 IPCC
SUPPLEMENT (Geneva, Switzerland: World Meteorological Organization and
the United Nations Environment Programme, February, 1992).
Descriptor terms: global warming; greenhouse effect; ozone; pinatubo;
greenhouse gases; global environmental problems; carbon dioxide; ozone