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The premise of anthropogenic (man-made) global warming theory is that greenhouse-gas
emissions from human activities—namely, the burning of
fossil fuels that release carbon dioxide—are rapidly
accelerating the warming of the Earth, as projected by computer
models.
An authoritative source for the theory is the IPCC, whose
most recent climate assessment states: “Most of the observed
increase in globally averaged temperatures since the mid-20th
century is very likely due to the observed increase in anthropogenic
[greenhouse gas] concentrations.”[125]
To those who subscribe to anthropogenic global warming theory,
reducing man-made carbon-dioxide emissions is the top priority
in the struggle to save the Earth from potentially catastrophic
changes in climate caused by a change in the composition of
the atmosphere.
 Carbon dioxide, one of a number of heat-trapping greenhouse
gases,[126] is emitted both naturally
and by human activities, such as coal-fired power production.[127]
The EIA reports that carbon-dioxide emissions from the burning
of petroleum, coal, and natural gas constituted 82 percent
of all U.S. man-made greenhouse-gas emissions in 2006.[128]
According to the IPCC, between 1970 and 2004, total greenhouse-gas
emissions increased 70 percent worldwide, while carbon-dioxide
emissions rose 80 percent.[129] As
of 2008, thirty-nine out of every 100,000 particles of the
atmosphere were carbon dioxide, a figure 40–45 percent
higher than before the start of the Industrial Revolution.[130]
Without question, then, industrialization has increased carbon-dioxide emissions—but
are human emissions significant enough to accelerate warming? Have they already
done so? Both the Earth’s average temperature and global carbon-dioxide
emissions increased during the twentieth century. But what should we make of
research showing recent warming on Mars and Pluto, planets without power plants
or automobiles? Is planetary warming simply a natural phenomenon? A better understanding
of the issues surrounding these and similar questions is needed, if policymakers
intend to craft prudent energy policies.
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According to David
J. C. MacKay, the burning of fossil fuels sends seven
gigatons (3.27 percent) of carbon dioxide into the atmosphere
each year, while the biosphere and oceans account for
440 (55.28 percent) and 330 (41.46 percent) gigatons,
respectively... “Burning fossil fuels, in contrast,”
writes MacKay, “creates a new flow of carbon that,
though small, is not cancelled.”
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Central to climate-change discussions is an examination of
just how much atmospheric carbon dioxide is attributable to
human activities, rather than to nature. Sixty-three percent
of survey respondents believed that human activity, such as
the burning of fossil fuels, is the greatest source of carbon-dioxide
emissions. While some estimate that the human share of atmospheric
carbon dioxide is as small as 3 percent—according to
David J. C. MacKay, professor of natural philosophy in the
Department of Physics at the University of Cambridge, the
burning of fossil fuels sends seven gigatons (3.27 percent)
of carbon dioxide into the atmosphere each year, while the
biosphere and oceans account for 440 (55.28 percent) and 330
(41.46 percent) gigatons, respectively[131]—total
human emissions have jumped sharply since the Industrial Revolution;
and it is this added atmospheric carbon that worries many.
MacKay writes that, yes, carbon is emitted naturally into
the atmosphere but that the atmosphere also sends carbon back
to the land and oceans and that these carbon flows have canceled
each other out for millennia. “Burning fossil fuels,
in contrast,” writes MacKay, “creates a new flow
of carbon that, though small, is not cancelled.”
Though the amount of additional carbon from human activities is dwarfed by
natural carbon levels, might the added carbon increase from humans be enough
to alter climate dynamics? Are humans to blame for global warming? If so, what
portion of the warming do we cause? Advancing the climate debate depends on
a clear understanding of emissions’ impacts.
 Though
a causal link between human carbon-dioxide emissions and accelerated
warming has not been proved, national policymakers broadly
support curbing carbon emissions via government regulation.
One way to lower emissions is to reduce or eliminate the burning
of carbon-based fuels, such as coal or natural gas. Another
option is to replace motor vehicles that run on petroleum-based
fuels with lower- or non-carbon-emitting vehicles, such as
electric cars. However, because the overwhelming majority
of our energy is derived from fossil fuels, such carbon-reduction
strategies are easier planned than implemented.
As an alternative—or at least until we find ways to displace fossil fuels
and conventional vehicles—financial instruments known as carbon offsets
are used to cancel out carbon emissions. Each carbon offset represents the reduction
of one metric ton of carbon dioxide through carbon-reducing activities like
tree planting or renewable energy production. The idea is to purchase enough
carbon offsets to reduce or cancel out one’s total carbon-dioxide contribution.
A plurality (45.6 percent) of respondents believed that carbon offsets are an
easy way to cancel out one’s carbon-dioxide emissions. Once again, however,
this is easier said than done.[132] In fact, some carbon
offsets represent activities that would have been carried out in any case. As
a result, the United States Federal Trade Commission is investigating the legitimacy
of the carbon-offsets business,133 and carbon offsets have come under fire in
Europe as well.[134]
Particularly
among industrialized nations, the U.S. is castigated for not
ratifying the Kyoto Protocol, an international agreement to
reduce greenhouse-gas emissions. However, several large carbon
emitters—namely China, India, and other “developing”
countries—did ratify the protocol but are exempted from
its costly carbon-reduction mandates.[135]
(According to Danish political scientist Bjørn Lomborg,
the annual cost of the Kyoto Protocol is $180 billion.)[136]
Considering the current and projected future emissions of
these nations, their exemption from the mandates is enormously
significant.
According to the EIA, collective carbon-dioxide emissions
from China and India are projected to account for 34 percent
of total world emissions in 2030, with China alone accounting
for 28 percent of the world total.[137]
The EIA[138] and the Netherlands Environmental
Assessment Agency[139] report that
China’s carbon-dioxide emissions from burning fossil
fuels surpassed those of the U.S. in 2006, and the EIA projects
China’s energy-related carbon-dioxide emissions to exceed
U.S. emissions by almost 15 percent in 2010 and by 75 percent
in 2030.[140] Given these estimates,
many Americans oppose agreeing to costly carbon-reduction
plans while China, India, and other nations are not similarly
bound.
Over 46 percent of respondents believed that reducing carbon
emissions will be simple and inexpensive, while a plurality
(48.6 percent) disagreed. Regardless of the means chosen to
reduce carbon-dioxide emissions, the task will be complex
and expensive.[141] Carbon taxes can
conceivably lead to higher costs on everyone—from corporations
to individuals—since everyone is responsible for at least
some of the carbon dioxide that enters the atmosphere. Likewise,
cap-and-trade systems and other carbon-reduction plans will
make energy more expensive, increasing expenses for producers
and raising costs for consumers.
The U.S. Senate struck down the most well-known cap-and-trade proposal to date,
the Lieberman-Warner bill,[142] largely
because of its projected costs.[143]
The bill called for reductions in greenhouse-gas emissions
of 15 percent below 2005 levels by 2020, 30 percent below
2005 levels by 2030, and 70 percent below 2005 levels by 2050.
One study estimated that reductions of this magnitude would,
by 2030, reduce GDP by up to $669 billion per year, cost households
an average of up to $6,752 per year, increase gasoline prices
up to 144 percent, increase electricity prices up to 129 percent,
increase natural gas prices up to 146 percent, and eliminate
up to 4 million jobs.[144] President
Obama’s plan is to require a reduction in greenhouse
gases of approximately 83 percent below 2005 levels by 2030.[145]
Fundamentally transforming the U.S. economy, which is firmly rooted in fossil-fuel-based
energy, is a daunting task. Whether we should do so is an important question.
Clearly, because of concerns about climate change and dependence on foreign
sources of energy, the U.S. will expand its use of renewable energies and alternative-transportation
fuels. Eventually, the U.S. might meet a large percentage of energy demand via
renewables, but such a feat will not be achieved quickly, nor will it come without
significant economic cost. Fostering economic prosperity and protecting the
environment are both important goals. Informed policymaking will require an
honest accounting of the time and expense that an energy-economy makeover could
entail.
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