Jacobson M.Z. Atmospheric Pollution
Подождите немного. Документ загружается.
were those during the last 1,000 years (Table 12.4), this argument does not explain
global warming.
Another proposed explanation for global warming has been that it is due to the nat-
ural variation in solar output. When sunspots appear, the intensity of the sun’s output
increases. A sunspot is a large magnetic solar storm that consists of a dark, cool cen-
tral core, called an umbra, surrounded by a ring of dark fibrils, called a penumbra.
As a result of the magnetic activity associated with sunspots, regions near the umbra
are hot, resulting in more net energy emitted by the sun when sunspots are present
than when they are absent. Sunspot number and size peak every 11 years, but because
the sun’s magnetic field reverses itself every 11 years, a complete sunspot cycle actual-
ly takes 22 years. The difference in solar intensity at the top of the Earth’s atmosphere
between times of sunspot maxima and minima is about 1.4 W m
2
, or 0.1 percent of
the solar constant. Although sunspots have been linked to changes in climate during
the course of a sunspot cycle, the fact that sunspot intensity varies relatively consis-
tently from cycle to cycle makes it difficult to link sunspots to multidecade increases
in temperatures.
A third proposed explanation has been that warming is due to natural internal
variability of the ocean atmosphere system. Internal variability results in sinusoidal
warming and cooling of the Earth’s climate. Whereas internal variability explains
part of the warming and cooling cycles between the 1850s and the present (seen in
Fig. 12.11), changes due to internal variability are on the order of /0.3C (Stott
et al., 2000), smaller than global observed temperature changes of 0.6 to 0.9C
since 1856.
12.4.2. Feedbacks of Gases to Climate
Whereas the simple radiative energy balance model introduced at the beginning of this
chapter described the equilibrium temperature of the Earth in the absence of natural
greenhouse gases, temperature changes in the real atmosphere depend not only on
greenhouse gases, but also on their feedbacks to clouds, winds, and the oceans.
Feedbacks will affect the magnitude of future global warming.
If an increase in emissions initially forces a warming of the climate, the climate
may respond either positively, enhancing the warming, or negatively, canceling the
warming. A positive feedback mechanism is a climate response mechanism that
causes temperatures to change further in the same direction as that of the initial
temperature perturbation. A negative feedback mechanism is a mechanism that caus-
es temperatures to change in the opposite direction from that of the initial temperature
perturbation. Positive feedbacks can lead to a runaway greenhouse effect, such as that
which occurred on Venus. Negative feedbacks tend to mitigate potential effects of
global warming. Next, some positive and negative feedback mechanisms resulting
from an initial increase in temperatures by greenhouse gases are listed.
• Water vapor – temperature rise positive feedback
If air temperatures initially increase, water evaporates from the oceans, increasing
atmospheric water vapor (a greenhouse gas), increasing temperatures further.
• Snow-albedo positive feedback
If air temperatures initially increase, sea ice and glaciers melt, decreasing the
Earth-atmosphere albedo, increasing incident solar radiation to the surface,
increasing temperatures further.
338 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION
• Water vapor – high cloud positive feedback
If air temperatures initially increase, water evaporates from the oceans, increas-
ing the cover of high clouds (made primarily of ice, which is relatively
transparent to solar radiation but absorbent of thermal-IR radiation), increasing
the absorption and reemission of the Earth’s thermal-IR radiation, increasing
temperatures further.
• Solubility – carbon dioxide positive feedback
If air temperatures initially increase, the solubility of carbon dioxide in ocean
water decreases, increasing the transfer of carbon dioxide from water to air,
increasing temperatures further.
• Saturation vapor pressure – water vapor positive feedback
If air temperatures initially increase, the saturation vapor pressure of water increas-
es, increasing the quantity of uncondensed water vapor in the air, increasing
temperatures further.
• Bacteria – carbon dioxide positive feedback
If air temperatures initially increase,
the rate at which soil bacteria decompose
dead organic matter into carbon dioxide and methane increases, increasing atmos-
pheric carbon dioxide levels, increasing temperatures further.
• Permafrost – methane positive feedback
If air temperatures initially increase, Arctic permafrost melts, enhancing release of
methane stored under the permafrost, increasing temperatures further.
• Water vapor – low cloud negative feedback
If air temperatures initially increase, water evaporates from the oceans, increasing
the cover of low clouds (made of liquid water, which reflects solar radiation),
increasing the effective Earth-atmosphere albedo, decreasing incident solar radia-
tion, decreasing temperatures.
• Plant – carbon dioxide negative feedback
If air temperatures initially increase, plants and trees flourish and photosynthesize
more, decreasing the quantity of carbon dioxide in the air, decreasing temperatures.
The only practical way to elucidate the relative importance of the different feed-
back mechanisms is through computer modeling of the climate. To date, climate models
accounting for feedbacks have found that increases in the atmospheric greenhouse
gases increase global near-surface temperatures and cool stratospheric temperatures,
consistent with theory and observations described in Section 12.3.1.
12.4.3. Effects of Aerosol Particles on Climate
Although all greenhouse gases warm near-surface air, some aerosol particle compo-
nents warm and others cool the air. Particle components that warm the air include
black carbon (BC), iron, aluminum, polycyclic aromatic compounds, and nitrated
aromatic compounds. These components warm the air primarily by absorbing solar
radiation, although they also absorb thermal-IR radiation. Most other particle compo-
nents, including water, sulfate, nitrate, and most organic compounds, cool near-surface
air by backscattering incident solar radiation to space more than they absorb thermal-
IR radiation from the Earth. A major unresolved issue is the extent to which warming
from absorbing particle components offsets cooling from other components. If only
instantaneous radiative effects are considered and time-dependent effects are ignored,
cooling caused by all reflective components appears to exceed the warming caused by
THE GREENHOUSE EFFECT AND GLOBAL WARMING 339
all absorbing components in the global average, but not by much. Instantaneous radia-
tive effects, however, tell only part of the story. A true estimate of the effect of aerosol
particles on climate requires the consideration of time-dependent effects as well. Some
time-dependent effects are summarized next.
The “Self-Feedback Effect”
When particles are emitted into to the air, they change the air temperature, relative
humidity, and surface area available for gases to condense upon, all of which affect the
composition, liquid water content, size, and optical properties of both the new and
existing particles. This process is called the self-feedback effect (Jacobson, 2002). For
example, when BC warms the air, it decreases the relative humidity, decreasing the liq-
uid water content and reflectivity of particles containing sulfate and nitrate, warming
the air further. Reduced aerosol particle liquid-w
ater also decreases the liquid-phase
chemical conversion of sulfur dioxide to sulfate and the dissolution of ammonia, nitric
acid, and hydrochloric acid into particles, further reducing particle size and reflectivity.
In addition, when BC is emitted in one location, it increases the surface area available
for sulfuric acid to condense upon, increasing the formation of sulfate upwind and
decreasing it downwind.
The “Photochemistry Effect”
Aerosol particles alter photolysis coefficients of gases, affecting their concentra-
tions and those of other gases (through chemical reactions). Because many gases
absorb solar and/or thermal-IR radiation,
changing the concentration of such gases
affects temperatures. The process by which aerosol particles change photolysis coeffi-
cients, thereby affecting temperatures, is the photochemistry effect (Jacobson, 2002).
The “Smudge-Pot Effect”
During day and night all aerosol particles trap the Earth’s thermal-IR radiation,
warming the air (Bergstrom and Viskanta, 1973; Zdunkowski et al., 1976). This warm-
ing is well known to citrus growers who, at night, used to burn crude oil in smudge
pots to fill the air with smoke and trap thermal-IR radiation, preventing crops from
freezing. The warming of air relative to a surface below increases the stability of air,
slowing surface winds (and increasing them aloft), reducing the wind speed dependent
emission rates of sea spray, soil dust, road dust, pollens, spores and some gas-phase
particle precursors. The reduction in concentration of these particles affects daytime
solar reflectivity and day-and nighttime thermal-IR heating. Changes in stability and
winds due to thermal-IR absorption by aerosols also affect energy and pollutant trans-
port. The effect of thermal-IR absorption by particles on emissions of other particles
and gases and on local energy and pollutant transport is referred to as the smudge-pot
effect (Jacobson, 2002).
The “Daytime Stability Effect”
If airborne particles absorb solar radiation, the air warms. Whether the particles
absorb or only scatter, they prevent solar radiation from reaching the surface, cooling
the surface and increasing the air’s stability (Bergstrom and Viskanta, 1973; Venkatram
and Viskanta, 1977; Ackerman, 1977). Like with the smudge-pot effect, enhanced day-
time stability slows surface winds, reducing emissions of wind-driven particles and
gases and affecting local pollutant and energy transport. This effect is called the day-
time stability effect (Jacobson, 2002).
340 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION
The “Particle Effect Through Surface Albedo”
During the day, airborne BC reduces sunlight to and cools the ground, increasing
the lifetime of existing snow. Conversely, because BC warms the air, snow passing
through a BC layer is more likely to melt. At night, airborne BC also enhances down-
ward thermal-IR, melting snow on the ground. Because the albedo of new snow
exceeds that of sea ice, which exceeds those of soil or water, the melting of snow or
sea ice increases sunlight to the surface. The effect of aerosol particles on temperatures
through their change in snow and sea-ice cover is the particle effect through surface
albedo.
The “Particle Effect Through Large-Scale Meteorology”
Aerosol particles affect local temperatures, which affect local air pressures, winds,
relative humidities, and clouds. Changes in local meteorology slightly shift the loca-
tions and magnitudes of semipermanent and thermal pressure systems and jet streams.
The effect of local particles on lar
ge-scale temperatures is the
particle effect thr
ough
large-scale meteorology.
The “Indirect Effect”
When pollution particles are emitted, more cloud-condensation nuclei (CCN) are
available for water vapor to condense on. If all else is the same, the addition of more
CCN produces more small cloud drops and fewer large cloud drops. For the same total
volume of water, a large number of small drops has a greater cross-sectional area,
summed among all drops, than does a small number of large drops. The greater cross-
sectional area of small drops in comparison with large drops means that adding CCN
to the air increases the reflectivity of sunlight, cooling the ground during the day
(Twomey, 1977). An increase in the number of small drops and a decrease in the num-
ber of large drops due to the addition of pollution particles also reduces rates of drizzle
in low clouds, thereby increasing the liquid water content and fractional cloudiness of
such clouds, further cooling the surface during the day (Albrecht, 1989). These two
effects of aerosol particles on clouds and, therefore, temperatures, are referred to as
indirect effects.
The “Semidirect Effect”
Solar absorption by a low cloud increases stability below the cloud, reducing verti-
cal mixing of moisture, thinning the cloud (Nicholls, 1984). Decreases in relative
humidity correlate with decreases in low cloud cover (Bretherton et al., 1995; Klein,
1997). Similarly, absorbing particles warm the air, decreasing its relative humidity and
increasing its stability, reducing low-cloud cover (Hansen et al., 1997; Ackerman et al.,
2000). Reduced cloud cover increases sunlight reaching the surface, warming the sur-
face in a process called the semidirect effect (Hansen et al., 1997).
The “BC-Low-Cloud-Positive Feedback Loop”
When BC reduces low-cloud cover by increasing stability and decreasing relative
humidity, enhanced sunlight through the air is absorbed by BC, further heating the air
and reducing cloud cover in a positive feedback loop, called the BC-low-cloud positive
feedback loop (Jacobson, 2002). Whereas CO
2
also warms the air by absorbing
thermal- and solar-near-IR radiation, reducing low cloud cover and enhancing surface
solar radiation in some cases, it absorbs solar radiation much less effectively than does
BC, so it partakes less in this positive feedback loop than does BC.
THE GREENHOUSE EFFECT AND GLOBAL WARMING 341
12.5 POSSIBLE CONSEQUENCES OF GLOBAL WARMING
CO
2
(g) mixing ratios are expected to increase from about 355 ppmv in 1990 to 540 to
970 ppmv in 2100. During that same period, global near-surface temperatures are esti-
mated to increase by 1.4 to 5.8C (IPCC, 2001). The possible consequences of global
warming are discussed next.
12.5.1. Rise in Sea Level
Increases in temperatures affect sea levels in at least two ways. First, higher tempera-
tures enhance the melting of ice sheets and glaciers, adding water to the oceans.
Second, because liquid water density decreases with increasing temperature, higher
temperatures cause water to expand and sea levels to rise. Historical changes in glob-
al temperature have been correlated with changes in sea levels. When temperatures
peaked 120 to 90 m.y.a., during the mid-Cretaceous period, the Earth’s polar caps
melted, sea levels rose to unprecedented levels, and 20 percent of continental land
flooded. Today, snow and ice cover 3.3 percent of the Earth’s total surface area. The
total ice volume is about 25 million km
3
. If this ice melts, the sea level will rise 65 m
above its current level. During the twentieth century, the sea level rose by about 10 to
25 cm. By the year 2100,
the sea level is expected to rise by another 10 to 90 cm
(IPCC, 2001).
Although the melting of ice sheets, glaciers, and sea ice and the corresponding rise
in sea level are of concern, a large increase in sea level is unlikely to occur during the
next 500 years. The largest sources of sea level rise would be the melting of the East
and West Antarctic Ice Sheets, the Greenland Ice Sheet, sea ice over the Arctic,
the
large valley and piedmont glaciers of southeast Alaska, and the glaciers of central
Asia. The West Antarctic Ice Sheet, based over water, is an order of magnitude smaller
than is the East Sheet, based over land. Thus, the West Sheet is less stable than is the
East Sheet (Stuiver et al., 1981). If melted, the East and West Sheets would raise the
sea level 55 to 60 m (Denton et al., 1971), with the West Sheet responsible for about
5 m of this rise (Mercer, 1978). If extreme global warming occurs, the West Sheet, as a
result of its relative instability, is more likely to collapse than is the East Sheet. A
collapse of the West Sheet would probably take about 500 years (Bentley, 1984).
Currently, the East Sheet may be increasing in size because of an increased water
vapor supply to the sheet resulting from higher global temperatures (Bentley, 1984).
Extended global warming could reverse this trend and ultimately cause a collapse of
the sheet, increasing sea levels by 50 to 55 m. Such a process, though, is likely to take
thousands of years (Crowley and North, 1991).
The main effect of sea level rise, even in small quantities, is the flooding of low-
lying coastal areas and the elimination of a few flat islands that lie just above sea
level. Bangladesh, the most densely populated country in the world, is particularly at
risk. A 1 m rise in sea level would displace about 17 million people from their homes.
New Orleans, Louisiana, which already lies below sea level, would similarly face a
danger of flooding. Tuvulu (Fig. 12.21) is a chain of nine coral atolls in the South
Pacific Ocean, about halfway between Hawaii and Australia. Tuvulu has a total land
area of 26 km
2
, about 0.1 times the size of Washington DC, a coastline that stretches
for 24 km and a population of about 10,000. An increase in sea level of 2 m could
eliminate the country.
342 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION
12.5.2. Changes in Regional Climate and Agriculture
Global warming is likely to cause regional and temporal variations in temperature.
The
number of extremely hot days is likely to increase and the number of extremely cold
days is likely to decrease. Droughts will increase in some areas and floods in others.
Precipitation intensity, averaged over the globe, and the number of extreme rainfall
events are expected to increase (IPCC, 1995). Changes in regional climates are likely to
shift the location of viable agriculture. Crops may flourish in areas that were once too
cold or too dry, but they may also die in regions that become too hot or too wet. It is dif-
ficult to determine whether global warming will cause a net long-term increase or
decrease in food supply, but it is fairly certain that locations of crop viability will shift
(Wuebbles, 1995).
Because plants grow faster when temperatures, carbon dioxide levels, or water
vapor levels mildly increase (plant–carbon dioxide negative feedback), it is expected
that in areas where only mild changes in temperature and moisture occur, agriculture
will flourish. In areas where extreme variations occur, agriculture will die out. Of
particular concern are subtropical desert regions of Africa, where temperatures are
already hot. In these regions, agriculture is subject to the whims of the climate, and
millions of people depend on the local food supply. Small changes in climate could
trigger famine, as has occurred in the past.
12.5.3. Changes in Ecosystems
Rapid, continuous increases in temperature could lead to the extinction of many
species that are accustomed to narrow climate conditions and are unable to migrate
faster than the rate of climate change. Although enhanced CO
2
(g) levels invigorate
forests, sharp increases in temperature could lead to forest dieback in tropical regions,
affecting the rates of CO
2
(g) removal by photosynthesis and emission by respiration.
THE GREENHOUSE EFFECT AND GLOBAL WARMING 343
Figure 12.21. Island of Fualopa, part of the Funafuti Atoll, one of nine coral atolls comprising
the country of Tuvulu. Fualopa is set aside for conservation and uninhabited, but it and all
other islands making up Tuvulu would be substantially eliminated if sea levels rose just a
couple of meters. Photo courtesy of Peter Bennetts.
12.5.4. Effects on Human Health
If global temperatures increase, people living in locations where temperatures are
already hot are likely to experience more stress and heat-related health problems
than are people living in milder climates. People currently living in cold climates are
likely to experience less stress. Heat-related health problems, such as heat rash and
heat stroke, generally affect the elderly and those suffering from illnesses more than
they affect the general population. Increases in precipitation as a result of global
warming could increase the populations of mosquitoes and other insects that carry
diseases.
CO
2
(g), CH
4
(g), and N
2
O(g) cause no direct harmful human health problems at
ambient mixing ratios (Section 3.6). Nevertheless, increases in the mixing ratios of
these gases will affect human health indirectly through the effects of these gases on
climate change and the effect of the resulting climate change on health. P
articulate
BC, another agent of global warming, will affect human health directly. BC is
emitted primarily in submicron particles. Epidemiological studies have shown
that long-term exposure to particles 2.5 m in diameter above background levels
causes increased mortality, increased disease, and decreased lung function in adults
and children (Özkatnak and Thurston, 1987; U.S. EPA, 1996; Pope and Dock
ery,
1999).
12.5.5. Effects on Stratospheric Ozone
Figure 12.12 shows that whereas global warming has caused a warming of near-
surface air since at least 1958, it has caused a cooling of the stratosphere. Cooling of
the stratosphere affects the ozone layer in at least three ways.
First, cooling affects the rates of chemical reactions that produce and destroy
ozone. Whereas many reactions proceed more slowly when temperatures decrease, the
reaction O(g)O
2
(g)M O
3
(g)M proceeds more rapidly when temperatures
decrease. Thus, when gas chemistry alone is considered, a cooling of the stratosphere
slightly increases global stratospheric ozone.
Second, cooling decreases the saturation vapor pressure (SVP) of water, allow-
ing sulfuric acid–water aerosol particles in the background stratosphere to grow
larger. The increase in size of these aerosol particles increases the rates at which
heterogeneous reactions occur on their surfaces. Because such reactions produce
chlorine gases that photolyze to products that destro
y ozone, a decrease in stratos-
pheric temperatures reduces global stratospheric ozone when only this effect is
considered.
Third, a cooling of the stratosphere increases the occurrence, size, and lifetime of
Polar Stratospheric Clouds (PSCs). Type I PSCs form at below 195 K and Type II
PSCs form at below 187 K. Stratospheric cooling decreases temperatures below these
critical levels during winter more frequently and for a longer period than when no
cooling occurs, increasing Type I and Type II PSC lifetime, and size, enhancing
Antarctic and Arctic ozone destruction during Southern and Northern Hemisphere
springtime, respectively.
In sum, stratospheric cooling resulting from near-surface global warming has
opposing effects on ozone in the global stratosphere, but it causes a net destruction of
ozone over the Antarctic and Arctic.
344 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION
THE GREENHOUSE EFFECT AND GLOBAL WARMING 345
Figure 12.22. Percentage of world carbon dioxide emissions by country or continent, 1997.
Source: Marland et al. (2000).
12.6. REGULATORY CONTROL OF GLOBAL WARMING
Global warming is an international problem because all nations emit greenhouse gases
and BC and are affected by changes in temperatures induced by such pollutants.
Figure 12.22 shows that the countries emitting the most greenhouse gases in 1997
were the United States, China, and Russia. All countries in Central and South America
and Africa combined emitted only 8.8 percent of the world total.
Figure 12.23 shows carbon emissions per capita by country in 1997. The figure
shows that per capita emission were highest in oil-producing countries, particularly
Qatar, the United Arab Emirates, and Kuwait. Yet, the populations of these countries are
relatively small, so the total emission from them was also small. The United States
stands out as having a high per capita emission rate as well as a large total emission rate.
Global warming is a divisive political issue because many industries depend on the
combustion of fossil fuels for their viability, and switching to alternative sources of
energy is often either uneconomical or otherwise undesirable. Many newly industrial-
ized nations, as well, find that increasing the use of fossil fuels is the most economical
means of expanding their economies.
Unlike with urban air pollution, acid rain, or global ozone problems, national and
international governments have done relatively little to control global w
arming. In the
United States, for example, no federal regulation to date has directly confronted the
threat of global warming. The Regulation of vehicle emissions (e.g., Table 8.1)
through the Clean Air Act Amendments has improved vehicle mileage, reducing
carbon dioxide indirectly. United States federal tax code incentives since the late
Oceania (5.0)
China (13.9)
Russia (5.9)
Japan (4.8)
India (4.2)
Germany (3.4)
Africa (3.3)
Central+South
America (5.5)
U.K. (2.2)
Canada (2.0)
Italy (1.7)
Other (19.6)
United States (22.6)
South Korea (1.8)
Poland (1.4) France (1.4)
Australia (1.3)
1970s for the development of renewable energy and for improvements in energy
efficiency have also addressed the issue indirectly. Nevertheless, simultaneous tax
incentives have existed for the development of fossil fuel energy sources. In the 1980s,
tax incentives for alternative energy sources were severely reduced, whereas those for
fossil fuels were enhanced.
The 1990 Clean Air Act Amendments required the U.S. EPA to publish a list iden-
tifying the potential effect of CFCs and their alternatives on global warming, so the
problem of global warming has been recognized increasingly. Whereas all countries
tax fuels to some extent, Denmark, the Netherlands, Finland, Norway, and Sweden
specifically implemented carbon taxes in the mid-1990s. Denmark taxed all carbon
dioxide emission sources, except gasoline, natural gas, and biofuel. The Netherlands
taxed all energy sources used as fuel. Finland taxed all fossil fuels. Norway taxed
mineral oil, gasoline, gas burned in marine oil fields, coal, and coke. Sweden taxed oil,
kerosene, natural gas, coal, coke, and other sources.
On May 9, 1992, an international agreement addressing global climate change,
hashed out in Rio de Janeiro, Brazil, was adopted at the United Nations. The agree-
ment, the United Nations Framework Convention on Climate Change, called on
signatory nations to develop current and projected emission inventories for greenhouse
gases, devise policies (to be implemented at a later meeting) for reducing greenhouse
gas emissions, and promote technologies for reducing emissions. By 1994, 184 nations
had signed the agreement and most had ratified it. In 1995, the nations involved in the
convention met in Berlin, Germany, to discuss details of the proposed policies and tar-
get dates for implementing them.
346 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION
0510
15 20
Qatar
United Arab Emirates
Kuwait
Singapore
United States
Australia
Canada
Saudi Arabia
Czech Republic
North Korea
Denmark
Netherlands
Belgium
Germany
Russia
South Korea
Japan
Poland
Taiwan
United Kingdom
Red: National emissions (hundred million tons of C per year)
Black: Per capita emissions (tons of C per person per year)
Figure 12.23. Per capita and national emissions of carbon (C) in carbon dioxide in 1997. The
figure includes only those countries emitting more than 10 million tons of C per year. Source:
Marland et al. (2000).
In December 1997, the nations met again for an 11-day conference in Kyoto,
Japan, to finalize the policies proposed at the Berlin meeting.
The conference resulted
in the Kyoto Protocol, an international agreement designed to control the emission of
greenhouse gases. The Kyoto Protocol called for industrialized countries to reduce
greenhouse gas emissions by 2008–2012. Such gases included carbon dioxide,
methane, nitrous oxide, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and
sulfur hexafluoride (SF
6
). Reductions in CO
2
(g), CH
4
(g), and N
2
O(g) emissions would
be relative to 1990 emissions. Reductions in the emission of others gases w
ould be rel-
ative to either 1990 or 1995 emissions. Table 12.5 lists the allocation of emission
reductions mandated for industrialized countries. Some countries were allowed to
increase emissions. The net change in emissions, weighted over all industrialized
countries, was 5.2 percent. Countries would be allowed to meet the reductions in one
of many ways. One mechanism would be to finance emission-reduction projects in devel-
oping countries, which were not subject to emission limits. Tree-planting, protecting
forests, improving energy efficiency, using alternative energy sources, reforming ener-
gy and transportation sectors, creating technologies with zero emissions, and reducing
emissions at their sources with existing technologies were other mechanisms.
By the end July 2001, 178 nations had signed the Kyoto Protocol. Although the
United States, the largest emitter of CO
2
(g) in the world, had signed (but not ratified)
the Protocol in 1997, the United States pulled out of the Protocol in 2001. One ration-
ale for the pullout was that controlling CO
2
(g) emissions would damage the U.S.
economy. The same argument w
as made by the automobile industry prior to the
passage of the Clean Air Act Amendments of 1970, which required 90 percent reduc-
tions of three pollutants from automobiles by 1976: CO, NO
x
, and hydrocarbons.
Despite opposition to them, the Amendments motivated U.S. automobile manufactur-
ers to invent the catalytic converter by 1975. The invention not only reduced pollutant
emissions as mandated, but also produced profitable patents. Neither the U.S. econo-
my nor the automobile industry suffered as a result of the 1970 regulations. From
1970–2000, for example, the number of vehicles in the United States doubled, where-
as the population increased by only one-third. The U.S. Gross Domestic Product in
fixed dollars also doubled and the unemployment rate decreased from 4.9 to 4.0 per-
cent during this period. Stringent air pollution regulations under the Clean Air Act
Amendments had no overall detrimental effect on the U.S. economy.
In the present case, a long-term method exists for the United States and other coun-
tries to reduce CO
2
(g) emissions toward satisfying the Kyoto Protocol. The method is
to shift a portion of electric generation from coal and natural gas to wind power. Since
the 1980s, wind turbine sizes and efficiencies have improved so that the direct cost of
THE GREENHOUSE EFFECT AND GLOBAL WARMING 347
Table 12.5. Percentage Change in Emissions Allowed for Industrialized Countries
under the Kyoto Protocol
Switzerland, central Europe, and European Union 8
United States 7
Canada, Hungary, Japan, Poland 6
Russia, New Zealand, Ukraine 0
Norway 1
Australia 8
Iceland 10
Countries Percentage Change in Emissions