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Behind the struggle to address global warming and climate change lies the
increase in greenhouse gases in our atmosphere
...
By increasing
the heat in the atmosphere, greenhouse gases are responsible for the
greenhouse effect, which ultimately leads to global warming
...
The basics of the phenomenon
were worked out by Svante Arrhenius in 1896
...

The sun bombards Earth with enormous amounts of radiation, which strike
Earth's atmosphere in the form of visible light, plus ultraviolet (UV), infrared
(IR) and other types of radiation that are invisible to the human eye
...
The remaining 70 percent
is absorbed by the oceans, the land and the atmosphere, according to NASA
...
The balance between incoming and outgoing
radiation keeps Earth's overall average temperature at about 59 degrees
Fahrenheit (15 degrees Celsius), according to NASA
...
Incoming UV radiation easily passes through the glass walls of
a greenhouse and is absorbed by the plants and hard surfaces inside
...

Indirect radiative effects
The false colors in this image represent concentrations of carbon monoxide
in the lower atmosphere, ranging from about 390 parts per billion (dark
brown pixels), to 220 parts per billion (red pixels), to 50 parts per billion
(blue pixels)
...
This happens in two main ways
...
For example, methane and carbon monoxide (CO) are
oxidized to give carbon dioxide (and methane oxidation also produces water
vapor; that will be considered below)
...
The peak of the thermal IR emission from Earth's surface is very close
to a strong vibrational absorption band of CO 2 (667 cm −1)
...
On the other hand, oxidation of methane to
CO 2,which requires reactions with the OH radical, produces an
instantaneous reduction, since CO 2 is a weaker greenhouse gas than
methane; but it has a longer lifetime
...
In any case, the calculation of the total radiative
effect needs to include both the direct and indirect forcing
...
For example, the destruction of non-methane volatile organic
compounds (NMVOCs) in the atmosphere can produce ozone
...

Methane has a number of indirect effects in addition to forming CO 2
...
Methane reacts with OH and so more methane means that the
concentration of OH goes down
...
The second
effect is that the oxidation of methane can produce ozone
...
CO and
NMVOC also produce CO 2 when they are oxidized
...
The

surprising effect of this is that the global warming potential of CO is three
times that of CO 2
...
Halocarbons
have an indirect effect because they destroy stratospheric ozone
...

Proportion of direct effects at a given moment
It is not possible to state that a certain gas causes an exact percentage of the
greenhouse effect
...
The higher ends of the
ranges quoted are for each gas alone; the lower ends account for overlaps
with the other gases
...

Atmospheric lifetime
Aside from water vapor, which has a residence time of about nine days,
major greenhouse gases are well mixed and take many years to leave the
atmosphere
...
Jacob (1999) defines the lifetime of an
atmospheric species X in a one- box model as the average time that a

molecule of X remains in the box
...
If one stopped pouring any of this gas into the box, then after a time,
its concentration would be about halved
...
Individual atoms or molecules may be lost
or deposited to sinks such as the soil, the oceans and other waters, or
vegetation and other biological systems, reducing the excess to background
concentrations
...

Carbon dioxide has a variable atmospheric lifetime, and cannot be specified
precisely
...

However, this excludes the balancing fluxes of CO 2 into the atmosphere
from the geological reservoirs, which have slower characteristic rates
...
Similar issues apply
to other greenhouse gases, many of which have longer mean lifetimes than
CO 2
...
g
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Earth's
surface temperature depends on this balance between incoming and outgoing
energy
...

A number of natural and man-made mechanisms can affect the global energy
balance and force changes in Earth's climate
...
Greenhouse gases in the
atmosphere absorb and re-emit some of the outgoing energy radiated from
Earth's surface, causing that heat to be retained in the lower atmosphere
...
Factors that influence Earth's energy balance can be
quantified in terms of "radiative climate forcing
...

Global warming potential
The global warming potential (GWP) depends on both the efficiency of the
molecule as a greenhouse gas and its atmospheric lifetime
...


Thus, if a gas has a high (positive) radiative forcing but also a short lifetime,
it will have a large GWP on a 20-year scale but a small one on a 100-year
scale
...
Carbon dioxide is
defined to have a GWP of 1 over all time periods
...
The 2007 IPCC
report lists the GWP as 72 over a time scale of 20 years, 25 over 100 years
and 7
...
A 2014 analysis, however, states that although
methane's initial impact is about 100 times greater than that of CO 2 , because
of the shorter atmospheric lifetime, after six or seven decades, the impact of
the two gases is about equal, and from then on methane's relative role
continues to decline
...

Examples of the atmospheric lifetime and GWP relative to CO 2 for several
greenhouse gases are given in the following table:
Atmospheric lifetime and GWP relative to CO 2 at different time horizon for
various greenhouse gases
...


The

phasing-out

of

less

active

HCFC-compounds will be completed in 2030
...

How greenhouse gases affect global warming
The gases in the atmosphere that absorb radiation are known as "greenhouse
gases" (sometimes abbreviated as GHG) because they are largely responsible
for the greenhouse effect
...
The most significant greenhouse gases are water
vapor (H O), carbon dioxide (CO), methane (CH) and nitrous oxide (N O),
according to the Environmental Protection Agency (EPA)
...


While some say that global warming is a natural process and that there have
always been greenhouse gasses, the amount of gasses in the atmosphere has
skyrocketed in recent history
...
Before, CO fluctuated
between about 180 ppm during ice ages and 280 ppm during interglacial
warm periods
...

Fluorinated gases — that is, gases to which the element fluorine was added
— including hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride,
are created during industrial processes and are also considered greenhouse
gases
...

Chlorofluorocarbons (CFCs), once used as refrigerants and aerosol
propellants until they were phased out by international agreement, are also
greenhouse gases
...
Its abundance in the atmosphere
2
...
Its global-warming potential
Carbon dioxide has a significant impact on global warming partly because of
its abundance in the atmosphere
...
S
...
Additionally, CO stays in the atmosphere for thousands of years
...

Sources of greenhouse gases
Some greenhouse gases, like methane, are produced through agricultural
practices including livestock manure management
...
The production of electricity is the source of 70
percent of the United States' sulfur dioxide emissions, 13 percent of nitrogen
oxide emissions, and 40 percent of carbon dioxide emissions, according to
the EPA
...
When trees are killed to produce goods or heat,
they release the carbon that is normally stored for photosynthesis
...


It's worth noting that forestry and other land-use practices offset some of
these greenhouse gas emissions, according to the EPA
...
Atmospheric carbon
dioxide is converted and stored in the vegetation and soils of the forest
...

Worldwide, the output of greenhouse gases is a source of grave concern:
From the time the Industrial Revolution began to the year 2009, atmospheric
CO levels have increased almost 38 percent and methane levels have
increased a whopping 148 percent, according to NASA, and most of that
increase has been in the past 50 years
...

"The warming we observe affects atmospheric circulation, which impacts
rainfall patterns globally
...

If these trends continue, scientists, government officials and a growing

number of citizens fear that the worst effects of global warming — extreme
weather, rising sea levels, plant and animal extinctions, ocean acidification,
major shifts in climate and unprecedented social upheaval — will be
inevitable
...


\

INTRODUCTION
A greenhouse gas (sometimes APPRECIATED GHG ) is a gas in an
atmosphere that absorbs and emits radiation within the thermal infrared
range
...

The primary greenhouse gases in Earth's atmosphere are water vapor , carbon
dioxide , methane , nitrous oxide , and ozone
...

In the Solar System, the atmospheres of Venus, Mars and Titan also contain
gases that cause a greenhouse effect
...

This increase has occurred despite the uptake of a large portion of the
emissions

by

various

natural

"sinks"

involved

in

the

carbon

cycle
...
e
...

It has been estimated that if greenhouse gas emissions continue at the present
rate, Earth's surface temperature could exceed historical values as early as
2047, with potentially harmful effects on ecosystems, biodiversity and the
livelihoods of people worldwide
...
As a result of human activities
concentrations in the atmosphere of so-called greenhouse gases, chiefly
carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are currently
at levels unseen for at least the last 650,000 years, and are rising at
unprecedented rates
...
Most
of the rest is a result of changes in land-use and a small proportion is the
product of burning calcium carbonate to produce cement
...

The greenhouse gases emitted as a result of human action enter the carbon
and nitrogen cycles
...

The Intergovernmental Panel on Climate Change believes that in order to
avoid the worst effects of climate change, at the very minimum greenhouse
gas concentrations need to be stabilised at 445–490 parts per million carbon
dioxide equivalent
...
At current rates of CO2 emission alone, the threshold of 445 parts per
million CO2e will be reached in a mere seven years, even sooner if the
accelerating output observed in the first few years of the present century
continues
...
Reduction in emissions from fossil fuel use is clearly of paramount
importance
...

But the management of fossil fuel use and adoption of carbon capture
technologies will not in themselves be sufficient to prevent serious climate
change in the next few decades
...
Such management has two fundamental components:
ensuring that existing carbon stocks held in natural ecosystems and in
agricultural areas remain secure; and attempting to increase the rate at which
carbon is sequestered in these systems
...

Similarly, warming at high latitudes will lead to at least partial melting of the
permanently frozen deep soil layer or permafrost there, releasing a
proportion of the vast amount of carbon stored in the permafrost into the
atmosphere
...
Overall, there also appears to be relatively little scope at present for
actively increasing carbon storage in most natural or largely natural
ecosystems
...
Large amounts of carbon are stored
in peat soils worldwide and in remaining tropical moist forests
...
Of particular importance are the tropical peat-swamp forests of
South-East Asia – ironically under threat of clearance for biofuel
production, despite the fact that their value as a carbon store hugely
outweighs any possible carbon benefits to be gained from the biofuel crops
that are replacing them
...
They often have highly depleted
soil carbon stocks, which could be replenished through the adoption of
appropriate techniques, such as conservation tillage and integrated nutrient
management using compost and manure
...

Not only is this technically possible, it is also economically feasible
...
At
this level of carbon pricing, forestry and agriculture combined become more
important than any other single sector
...

There still remain many challenges to effective implementation
...
Overcoming such barriers will
need a commitment to capacity-building on a very extensive scale
...

If the global community can rise to these challenges, the Earth’s living
systems can play a vital role in the struggle to avoid dangerous climate
change
...
This opportunity to
contribute to so many important environmental goals should not be missed
...
giss
...
gov)
 Karl TR, Trenberth KE(2003)
...
nasa
...

Esrl
...
gov
 Mora
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GREENHOUSE GASES

BY
PHILIP OLUKA
13/EG/PE/508
PETROLEUM ENGINEERING,
FACULTY OF ENGINEERING,
UNIVERSITY OF UYO
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JULY,2016

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