GREENHOUSE GAS
A greenhouse gas (sometimes abbreviated GHG) is a
gas in an atmosphere which absorbs and emits radiation within the
thermal infrared range. This process is the fundamental cause of the
greenhouse effect. The main greenhouse gases in the World's
atmosphere are carbon dioxide, water vapor, nitrous oxide, methane
and ozone. In the Solar System, the atmospheres of Venus, Mars, and
Titan also contain gases that cause greenhouse effects. Greenhouse
gases greatly affect the temperature of the Earth; without which
Earth's atmospheric temperature will be on an average of about 59 °F
(33 °C) colder than at present. United States was responsible for
20% of the world's greenhouse gases emitted in 1997.
Historically, since Industrial Revolution the burning of fossil
fuels has contributed to the increase in carbon dioxide in the
atmosphere from 280ppm to 390ppm, despite the uptake of a large
portion of the emissions through various natural "sinks" involved in
the carbon cycle. Carbon dioxide emissions come from combustion of
carbonaceous fuels such as coal, petrochemical compounds, oil, and
natural gas. CO2 is a product of ideal, stoichiometric combustion of
carbon, although few combustion processes are ideal, and burning
coal for example, also produces carbon monoxide. Since 2000 fossil
fuel related carbon emissions have equaled or exceeded the IPCC's
"A2 scenario", except for small dips during two global recessions.
FOSSIL FUELS
Fossil fuels are fuels formed by natural processes such as anaerobic
decomposition of buried dead organisms. The age of the organisms and
their resulting fossil fuels is typically millions of years, and
sometimes exceeds 650 million years.[1] The fossil fuels, which
contain high percentages of carbon, include coal, petroleum, and
natural gas. Fossil fuels range from volatile materials with low
carbon: hydrogen ratios like methane, to liquid petroleum to
nonvolatile materials composed of almost pure carbon, like
anthracite coal. Methane can be found in hydrocarbon fields, alone,
associated with oil, or in the form of methane clathrates. It is
generally accepted that they formed from the fossilized remains of
dead plants [2] by exposure to heat and pressure in the Earth's
crust over millions of years.[3] This biogenic theory was first
introduced by Georg Agricola in 1556 and later by Mikhail Lomonosov
in the 18th century.
It was estimated by the Energy Information Administration that in
2007 primary sources of energy from fossil fuels consumed in the
world consisted of following:
- Petroleum: 36.0%
- Coal:
27.4%
- Natural gas: 23.0%
- TOTAL:
86.4% share for fossil fuels
Non-fossil sources in 2006 included hydroelectric 6.3%,
nuclear 8.5%, and others (geothermal, solar, tide, wind, wood,
waste) amounting to 0.9 percent. World energy consumption was
growing about 2.3% per year.
Fossil fuels are non-renewable resources because they take millions
of years to form, and reserves are being depleted much faster than
new ones are being made. The production and use of fossil fuels
raise environmental concerns. A global movement toward the
generation of renewable energy is therefore under way to help meet
increased energy needs.
The burning of fossil fuels produces around 21.3 billion tonnes
(21.3 gigatonnes) of carbon dioxide (CO2) per year, but it is
estimated that natural processes can only absorb about half of that
amount, so there is a net increase of 10.65 billion tonnes of
atmospheric carbon dioxide per year (one tonne of atmospheric carbon
is equivalent to 44/12 or 3.7 tonnes of carbon dioxide).[6] Carbon
dioxide is one of the greenhouse gases that enhances radiative
forcing and contributes to global warming, causing the average
surface temperature of the Earth to rise in response, which the vast
majority of climate scientists agree will cause major adverse
effects.
Environmental Effects
Global fossil carbon emission by fuel type, 1800-2007. Note: Carbon
only represents 27% of the mass of CO2. In the United States, more
than 90% of greenhouse gas emissions come from the combustion of
fossil fuels. Combustion of fossil fuels also produces other air
pollutants, such as nitrogen oxides, sulfur dioxide, volatile
organic compounds and heavy metals.
According to Environment Canada:
"The electricity sector is unique among industrial sectors in its
very large contribution to emissions associated with nearly all air
issues. Electricity generation produces a large share of Canadian
nitrogen oxides and sulphur dioxide emissions, which contribute to
smog and acid rain and the formation of fine particulate matter. It
is the largest uncontrolled industrial source of mercury emissions
in Canada. Fossil fuel-fired electric power plants also emit carbon
dioxide, which may contribute to climate change. In addition, the
sector has significant impacts on water and habitat and species. In
particular, hydro dams and transmission lines have significant
effects on water and biodiversity."
Carbon dioxide variations over the last 400,000 years,
showing a rise since the industrial revolution. According to U.S.
Scientist Jerry Mahlman and USA Today: Mahlman, who crafted the IPCC
language used to define levels of scientific certainty, says the new
report will lay the blame at the feet of fossil fuels with "virtual
certainty," meaning 99% sure. That's a significant jump from
"likely," or 66% sure, in the group's last report in 2001, Mahlman
says. His role in this year's effort involved spending two months
reviewing the more than 1,600 pages of research that went into the
new assessment.
Combustion of fossil fuels generates sulfuric, carbonic, and nitric
acids, which fall to Earth as acid rain, impacting both natural
areas and the built environment. Monuments and sculptures made from
marble and limestone are particularly vulnerable, as the acids
dissolve calcium carbonate.
Fossil fuels also contain radioactive materials, mainly uranium and
thorium, which are released into the atmosphere. In 2000, about
12,000 tonnes of thorium and 5,000 tonnes of uranium were released
worldwide from burning coal. It is estimated that during 1982, US
coal burning released 155 times as much radioactivity into the
atmosphere as the Three Mile Island incident. However, this
radioactivity from coal burning is minuscule at each source and has
not shown to have any adverse effect on human physiology.
Burning coal also generates large amounts of bottom ash and fly ash.
These materials are used in a wide variety of applications,
utilizing, for example, about 40% of the US production.
Harvesting, processing, and distributing fossil fuels can also
create environmental concerns. Coal mining methods, particularly
mountaintop removal and strip mining, have negative environmental
impacts, and offshore oil drilling poses a hazard to aquatic
organisms. Oil refineries also have negative environmental impacts,
including air and water pollution. Transportation of coal requires
the use of diesel-powered locomotives, while crude oil is typically
transported by tanker ships, each of which requires the combustion
of additional fossil fuels.
Environmental regulation uses a variety of approaches to limit these
emissions, such as command-and-control (which mandates the amount of
pollution or the technology used), economic incentives, or voluntary
programs.
An example of such regulation in the USA is the "EPA is implementing
policies to reduce airborne mercury emissions. Under regulations
issued in 2005, coal-fired power plants will need to reduce their
emissions by 70 percent by 2018.".
In economic terms, pollution from fossil fuels is regarded as a
negative externality. Taxation is considered one way to make
societal costs explicit, in order to 'internalize' the cost of
pollution. This aims to make fossil fuels more expensive, thereby
reducing their use and the amount of pollution associated with them,
along with raising the funds necessary to counteract these factors.
Former CIA Director James Woolsey recently outlined the national
security arguments in favor of moving away from fossil fuels.
REFERENCES
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