An exclusive project report on Green-House Effect. This project report will help you to learn about: 1. Meaning of Green-House Effect 2. Sources of Green-House Effect 3. Causes 4. Green-House Gases Present in the Atmosphere 5. Green-House Effect and Carbon Dioxide 6. Green-House Effect and Methane 7. List of Green-House Gases in the Atmosphere.
Contents:
- Project Report on the Meaning of Green-House Effect
- Project Report on the Sources of Green-House Effect
- Project Report on the Causes of Green-House Effect
- Project Report on Green-House Gases Present in the Atmosphere
- Project Report on Green-House Effect and Carbon Dioxide
- Project Report on Green-House Effect and Methane
- Project Report on List of Green-House Gases in the Atmosphere
Project Report # 1. Meaning of Green-House Effect:
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Our Earth is the third planet in the solar system. It revolves around the Sun. The Earth gets its heating energy from the rays of the sun. These rays are filtered down to the surface of the Earth through the layer of gases (atmosphere) which surrounds the Earth.
While most of the rays of the sun reach the Earth’s surface, some of the rays are also reflected back out of the atmosphere. The heat of the sun’s rays is then absorbed by the Earth’s surface and that too is radiated back into the layer of atmospheric gases.
As the sunray travels through the atmosphere and reaches the Earth, the following events take place:
i. A total of 26% of the sun’s energy is reflected by the atmosphere and the clouds back into the space. Around 6% is scattered by the atmosphere and the remaining 20% is reflected by the clouds.
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ii. About 19% of the energy is absorbed by the atmosphere (gases like the ozone and other particles present in the atmosphere) and the clouds.
iii. The remaining 55% reaches the Earth.
iv. Of this 55%, 4% is reflected back into the space by the Earth’s surface and the remaining 50% is absorbed by it.
v. The energy trapped by the Earth’s surface heats up the planet. It causes melting of ice and snow on the Earth and evaporation of water from various water bodies.
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vi. The heat absorbed by the Earth’s surface is released in the form of infrared radiations that are directed to the space.
vii. However, only a little amount of this heat is able to escape into the space as most of it is absorbed by the green-house gases in the Earth’s atmosphere. These gases radiate heat in the infrared range both out to the space and back to the Earth.
Majority of the radiation is directed back towards the Earth. This heats up the Earth and the Earth again radiates this energy in the form of infrared radiations. This cycle keeps repeating until there are no more infrared radiations are available for absorption.
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When this happens, some of this heat is absorbed by the atmospheric gases and some is allowed to escape back into space. This process is known as the ‘Green-house Effect’. The green-house effect was discovered by Joseph Fourier in 1824.
The green-house effect may therefore be defined as the progressive warming up of the earth’s surface due to blanketing effect of some a gases.
There are some specific gases in the atmospheric layer which trap this heat which is emitted back from the surface of the Earth. These gases are known as ‘Green-house Gases’. The four major green-house gases, which cause adverse effect, are carbon dioxide (CO2), Methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons (CFCs). Among these CO2 is the most common and important green-house gas.
Ozone (O3) and Sulphur dioxide (SO2) also act as serious pollutants with causing global warming. Thus, if the amount of these gases increases in the atmospheric layer, it is usual to expect that more and more of the heat emitted by the surface of the Earth will get trapped within this atmospheric layer and will not escape back into space.
Project Report # 2. Sources of Green-House Effect:
Table 1 shows some green-house gases their concentration Hill 21003 and sources of their emission.
As this keeps on happening, the Earth will become warmer and warmer. This process is also commonly known as the process of ‘Global Warming’. The process of green-house effect on earth is quite similar to a green-house. A green-house is a house made out of glass. It is used to grow plants in the winter season.
In the green-house the rays of the sun come in via the glass, and then the heat remains trapped within the glass walls and is not allowed to escape. In this manner the temperature inside the green-house remains high from outside and allows the plant to grow during the winter season as well.
Mainly human beings are responsible for what is happening to the Earth. The production of Green-house Gases is largely due to the burning of fossil fuels such as petroleum, coal and natural gas and also the burning of rain forests. This has served to speed up the Green-house Effect process which happens naturally. This is also, therefore, referred to as the “Man-Made Green-house Effect’.
As mentioned before, the increasing heat which remains trapped within the atmospheric layer will end up creating warmer climates across the globe. This process will significantly cause various climatic disturbances all over the Earth. This can result in many problems in the long run.
To combat this rising threat of global warming, countries all over the world are trying to create pollution free environment and planting trees. Re-forestation is a very natural method of creating an environment where global warming can be controlled as plants and trees actually absorb carbon dioxide and release oxygen into the atmosphere.
Automobile companies are focusing on manufacturing ‘Green’ cars which release reduced amounts of pollutants into the atmosphere. In the solar system the atmosphere of Venus, Mars and Titan also contains gases that cause green-house effect.
If an ideal thermally conductive blackbody was at the same distance from the Sun as the Earth is, it would have a temperature of about 5.3 °C.
However, since the Earth reflects about 30% (or 28%) of the incoming sunlight, the planet’s effective temperature (the temperature of a blackbody that would emit the same amount of radiation) is about -18 or -19°, about 33° C below the actual surface temperature of about 14°C or 15°C.
The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the green-house effect.
Solar radiation at the high frequencies of visible light passes through the atmosphere to warm the planetary surface, which then emits this energy at the lower frequencies of infrared thermal radiation. Infrared radiation is absorbed by green-house gases, which in turn re-radiates much of the energy to the surface and lower atmosphere.
The mechanism is named after the effect of solar radiation passing through glass and warming a green-house, but the way it retains heat is fundamentally different as a green-house works by reducing airflow, isolating the warm air inside the structure so that heat is not lost by convection.
Green-house gases-including most diatomic gases with two different atoms (such as carbon monoxide, CO) and all gases with three or more atoms-are able to absorb and emit infrared radiation.
Though more than 99% of the dry atmosphere is IR transparent (because the main constituents – N2, O2, and Ar-are not able to directly absorb emit infrared radiation), intermolecular collisions cause the energy absorbed and emitted by the green-house gases to be shared with the other, non-IR-active, gases.
In our solar system, Mars, Venus, and the Moon Titan also exhibit green-house effect. Titan has an anti-green-house effect, in that its atmosphere absorbs solar radiation but is relatively transparent to infrared radiation. Pluto also exhibits behaviour superficially similar to the anti-green-house effect.
A runaway green-house effect occurs if positive feedbacks lead to the evaporation of all green-house gases into the atmosphere. A runaway green-house effect involving carbon dioxide and water vapour is thought to have occurred on Venus.
Thus green-house effect can be defined as the process by which the green-house gases in the Earth’s atmosphere trap heat of the sun and prevents the Earth from freezing in the absence of sunlight’. Green-house effect is a natural phenomenon which prevents stark temperature fluctuations on the Earth during day and night.
There are green-house gases like carbon dioxide, water vapour and methane in the Earth’s atmosphere that prevent the energy of the sun from being radiated out into the space by the Earth’s surface. Without these gases, the temperature of the Earth would plummet to -18° rather than the normal 15°.
In 2005, the world’s top-20 emitters comprised 80% of total GHG emissions. Tabulated below are the top-5 emitters for the year 2005. The second column is the country’s or region’s share of the global total of annual emissions. The third column is the country’s or region’s average annual per capita emissions, in tonnes of GHG per head of population.
Project Report # 3. Causes of Green-House Effect:
i. Deforestation:
One of the man-made causes of the Green-house effect is deforestation. Deforestation increases the amount of carbon-di-oxide in the atmosphere. Also, due to the disappearance of trees, photosynthesis cannot take place.
Deforestation is rampant today due to the increase in human population. The levels of deforestation have increased by about nine per-cent in recent years. Also, the burning of wood causes it to decay, therefore releasing more carbon-dioxide into the atmosphere.
ii. Industrial Emission:
Green-house Gases are also released into the atmosphere due to the burning of fossil fuels, oil, coal and gas. These materials are used increasingly and rampantly in Industries. Therefore Industries are also a major cause of the Green-house Effect. Manufacturing of goods also leads to an increase in the level of green-house gases.
Burning of coal and natural gas to run the factories has led to the dangerous rise of carbon dioxide and methane. This has a radical impact on the green-house effect and contributes to global warming. Since the chimneys are tall, fumes get mixed to the air directly and are responsible for trapping more heat and increasing it.
iii. Electrical Emission:
Another man-made cause of the increase in the Green-house effect is due to the emission of such gases from all electrical appliances. Refrigerator in the house emits gases.
These gases are known as chlorofluorocarbons (CFCs) and are also used in refrigerators, aerosol cans, some foaming agents in the packaging industry, fire extinguisher chemicals and cleaners used in the electronic industry all contribute to the green-house effect. Some processes of the cement manufacturing industries also act as a cause towards the Green-house effect.
iv. Fuel Burning:
Other man-made processes that contribute and are a cause to the Green-house effect are burning of gasoline, oil and coal. Apart from these, some farming and land-use processes are also a cause of the Green-house effect.
Most factories also produce many gases which last for a longer time in the atmosphere. These gases contribute to the green-house effect and also to the global warming on the planet. These gases are not naturally available in the atmosphere.
The burning of fossil fuels like petrol, diesel i.e. emissions from automobiles increase the amount of carbon dioxide in the environmental. Other gases like carbon monoxide and sulphur dioxide are also emitted from the exhaust pipes of vehicles. These gases contribute towards air pollution, which causes a dramatic addition of green-house gases in the atmosphere.
v. Population:
Population growth also is an indirect contributor and one of the causes of the Green-house effect. With the increase in population, the needs and wants of the people increase. Therefore, this increases the manufacturing processes as well as the industry processes.
This results in the increase of the release of industrial gases which catalysed the green-house-effect. The increase in population also results in the increase of agricultural processes. Most man-made machines, like the automobiles also contribute to the green-house effect.
There can be a number of reasons for green-house gases leading to global warming, some pertaining to human activity.
Dramatic and unpredictable climate change is a matter of concern these days. The extreme temperatures in the climate have affected not only human life, but also the flora and fauna. Human activities like deforestation, pollution etc. are the main cause of the rise in atmospheric temperature, which, according to some claims, is resulting in global warming.
There are natural green-house gases like water vapor, ozone, methane, carbon dioxide and nitrous oxide that are present in the atmosphere. These naturally existing green-house gases absorb the heat and maintain the optimum atmospheric temperature. The upper stratum of the atmosphere is covered by a layer of ozone, which protects the Earth from harmful UV rays of the sun.
The sun emits different kinds or rays that enter the atmosphere through the ozone layer. Certain rays are reflected back by this protective layer. The green-house gases circulate the heat evenly in the environment.
However, these days due to several human activities, a new set of green-house gases have been added to the atmosphere. These are hydro-fluorocarbons, sulphur hexafluoride, chlorofluorocarbons and per-fluorocarbons.
The man made green-house gases have a drastic effect on the ozone layer, since they deplete it and are called ozone holes. These make it easy for the sun’s harmful UV rays to pass through and affect the life on Earth. There is also a considerable rise in temperature, making it difficult to survive. Scientists are trying to figure out ways for bringing down this rapid increase in temperature.
There are many drastic downsides of global warming in the form of melting of icebergs, increased depletion of the ozone layer and unsteady weather changes. The annual emissions of green-house gases has risen up and is a cause of grave concern among scientists, since it leads to a slow but sure path towards the destruction of the planet.
Project Report # 4. Green-House Gases Present in the Atmosphere:
Green-house gases (GHG) are gaseous components in the atmosphere that contribute to the “green-house effect”, the heating of the Earth by means of a similar effect produced by the glass panes of a green-house. Green-house gases allow light from the sun to enter the atmosphere surrounding the Earth.
When that sunlight strikes the planet, some of it is reflected back towards space as infrared radiation, or heat. The GHGs in the atmosphere traps the heat, but the amount of energy sent from the sun to the Earth’s surface should be nearly the same as the amount of energy radiated back into space, leaving the temperature of the planet’s surface constant.
Some GHGs, such as water vapor, carbon dioxide, methane, ozone, and nitrous oxide, occur naturally to some extent in the atmosphere. Human activities add to the levels of these naturally occurring gases.
Green-house gases from industry and agriculture have played a major role in global warming. The increase in the population of the planet has to have some effect on the GHGs in the atmosphere, because more people are breathing out carbon dioxide, and deforestation to make houses for those people has resulted in fewer trees producing oxygen.
The burning of fossil fuels also leads to higher concentration of carbon dioxide, which constitutes about 76% of all the green-house gases in the Earth’s atmosphere. Most of the increase in carbon dioxide has occurred during the last 50 years. Measurements from Antarctic ice core samples have shown that carbon dioxide concentrations stayed pretty stable for about 10,000 years, but began rising in the mid-20th century.
Methane gas accounts for about 13% of the GHGs in the atmosphere. Since 1750, the amount of methane gas in the atmosphere has doubled, and some scientists say that amount could double again by 2050. Each year nearly 500 tons of methane is added to the air by coal mining, drilling for oil and natural gas, landfill emissions, wetland changes, and pipeline losses.
New style fully vented septic systems, Livestock and paddy rice farming, CFCs used in refrigeration systems, and halons in fire suppression systems are also sources of atmospheric methane. Most GHGs take a very long time to leave the atmosphere, but methane stays in the atmosphere for only 10 years. However, it traps 20 times more heat than carbon dioxide.
Animals release methane to the environment as a result of herbaceous digestion. It is believed that the addition of methane from this source has more than quadrupled over the last century. Termites also release methane through similar processes.
Methane is also released from landfills, coal mines, and gas and oil drilling. Landfills produce methane as organic wastes decompose over time. Coal, oil, and natural gas deposits release methane to the atmosphere when these deposits are excavated or drilled.
The average concentration of nitrous oxide (N2O) in the atmosphere is now increasing at a rate of 0.2 to 0.3% per year. Sources for this increase include land- use conversion; fossil fuel combustion; biomass burning; and soil fertilization. Most of the nitrous oxide added to the atmosphere each year comes from deforestation and the conversion of forests, savanna and grassland ecosystem into agricultural fields and grassland.
Both of these processes reduce the amount of nitrogen stored in living vegetation and soil through the decomposition of organic matter. Nitrous oxide is also released into the atmosphere when fossil fuels and biomass are burnt. However, the combined contribution of these sources to the increase of this gas in the atmosphere is thought to be minor.
The use of nitrates and ammonium fertilizers to enhance plant growth is another source of nitrous oxide. Accurate measurements of how much nitrous oxide is being released from fertilization have been difficult to obtain. Estimates suggest that the contribution from this source may represent for 50% to 0.2% nitrous oxide added to the atmosphere annually.
Nitrous oxide, primarily used as “laughing gas”, an inhaled anesthetic, is released naturally from oceans and by bacteria in soils. Nitrous oxide gas production has risen by more than 15% since 1750, and now makes up approximately 6% of the GHGs in the atmosphere.
Each year about 7-13 million tons is released into the atmosphere using nitrogen-based fertilizers, disposing of human and animal waste in sewage treatment plants, automobile exhaust. Use of Nitrogen-based fertilizers has doubled in the past 15 years. The nitrous oxide being released into the atmosphere today will be trapped in there 100 years from now.
Ozone’s role in the enhancement of the green-house effect has been difficult to determine scientifically. Accurate measurements of past long-term (more than 25 years in the past) levels of this gas in the atmosphere are currently unavailable. Concentrations of ozone gas are found in two different regions of the Earth’s atmosphere.
The majority of the ozone (about 97%) found in the atmosphere is localized in the stratosphere at an altitude of 15 to 55 kilometer above the Earth’s surface. In recent years, the concentration of the stratospheric ozone has been decreasing because of the buildup of chlorofluorocarbons in the atmosphere (see Lecture 7e).
Since the late 1970s, scientists have discovered that total column ozone amounts over Antarctica in the springtime have decreased by as much as 70% Satellite measurements have indicated that the ozone from 65° North to 65° South latitude has had a 3% decrease in stratospheric ozone since 1978.
Ozone is also highly concentrated at the Earth’s surface. Most of this ozone is created as an artificial byproduct of photochemical smog.
Since the beginning of the Industrial Revolution, the concentrations of many GHGs in the Earth’s atmosphere have steadily increased. In 1992, the United Nations held a Conference on Environment and Development to have a treaty aimed at reducing emission of green-house gases in order to combat global warming.
The treaty is called the United Nation Framework Convention on Climate Change (UNFCCC) which was established in 2005.
The world’s leading authority on global warming is the Intergovernmental Panel on Climate Change (IPCC). The IPCC has predicted that global warming will have severe impact on human health, natural ecosystem, agriculture, and coastal communities if steps are not taken immediately to reverse the increasing concentrations of GHGs in the Earth’s atmosphere.
The IPCC has concluded by consensus that “The balance of evidence suggests a discernible human influence on global climate”. That “human influence” is the increased level of green-house gases being released into the atmosphere and stronger steps must be taken towards reversing the trend before it is too late to repair the damage.
In summary, the green-house effect causes the atmosphere to trap more heat energy at the Earth’s surface and within the atmosphere by absorbing and re- emitting long wave energy. Of the long wave energy emitted back to space, 90% is intercepted and absorbed by green-house gases.
Without the green-house effect the Earth’s average global temperature would be – 18° Celsius, rather than the present 15° Celsius. In the last few centuries, the activities of human have directly or indirectly caused the concentration of the major green-house gases to increase. Scientists predict that this increase may enhance the green-house effect making the planet warmer.
Some experts estimate that the Earth’s average global temperature has already increased by 0.3 to 0.6° Celsius, since the beginning of this century, because of this enhancement. Predictions of future climate indicate that by the middle of the next century the Earth’s global temperature may be 1 to 3° Celsius higher than today.
According to a recent study, an average household in the United States contributes about 35,000 pound of green-house gases, such as carbon dioxide, into the atmosphere annually. No wonder we are running towards the dooms day at such an alarming speed.
The term ‘green-house gases’ is used to refer to the gases present in the atmosphere, which absorb the radiation and emit them within the thermal infrared range. These gases affect the temperature of the earth significantly.
In fact it is assumed that the absence of these gases would have made the temperature of the earth surface around 59 degree Fahrenheit colder than what it is at present. The most prominent green-house gases in the Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, ozone and CFCs.
When amount of these green-house gases increase in atmosphere they start to trap the solar radiations, which eventually leads to a rise in the surface temperature. This heating of Earth’s surface is known as green-house effect or green-house warming.
Although they heat up the surface of the Earth, they simultaneously cool the stratosphere, which eventually triggers ozone layer depletion also called as ozone hole. Ozone layer is very important for us, considering the vital role it plays by barring the UV rays from entering the atmosphere of the Earth.
Green-house gases are the gases which trap the solar radiations and trigger a rise in temperature levels on the planet. There are various green-house gases, the most prominent ones being carbon dioxide and chlorofluorocarbons (CFCs). Some other examples are methane, nitrous oxide and, water vapour.
Water Vapour:
Water vapor is the gaseous form of water, which is produced due to evaporation of water and/or sublimation of ice. The atmosphere of the Earth witnesses continuous production of water vapour due to immense amount of evaporation from water bodies. Eventually, this water vapour is removed from the atmosphere by the process of condensation.
Water vapour, approximately constitutes about 33 to 66 percent of green-house gases, thus becoming the most prominent constituent of green-house gases list. Anthropogenic factors, i.e. human activities do contribute in formation of water vapour, but the amount of vapour produced in this case is relatively negligible.
Ozone:
Another gas prominently featuring in the green-house gases list is Ozone constituting approximately 3 to 7 percent of green-house gases. Ozone absorbs 9 to laum in the IR region. Ozone, in upper troposphere acts as a green-house gas, while at ground level it acts as an air pollutant.
It is harmful for respiratory system of animals and human. As a green-house gas, ozone absorbs the infra-red energy that is emitted by the earth. It is assumed that the radiative forcing of ozone present in troposphere is approximately 25 percent more than that of carbon dioxide.
Ozone is made of three oxygen atoms (O3). The oxygen we find in our atmosphere is made up to two oxygen atoms (O2). Because of its chemical formulation, a single atom of oxygen (O) is unstable. That is, it wants to combine with something else.
That is why oxygen is almost found in pairs, in its O2 (diatomic) form, where it is more stable. O3 is less stable than O2 because it wants to return to the diatomic state by giving up an oxygen atom.
When enough ozone molecules are present, it forms a pale blue gas. It is an unstable molecule that readily combines with other atoms. Ozone has the same chemical structure whether it is found in the stratosphere or the troposphere.
In the troposphere, the ground-level or “bad” ozone is an air pollutant that damages human health, vegetation, and many common materials. It is a key ingredient of urban smog. In the stratosphere, the ozone found is that protects life on earth from the harmful effects of the sun’s ultraviolet rays.
Ozone is constantly being formed in the earth’s atmosphere by the action of the sun’s ultraviolet radiation on oxygen molecules. Ultraviolet light splits the molecules apart by breaking the bonds between the atoms. A highly reactive free oxygen atom then collides with another oxygen molecule to form an ozone molecule. Because ozone is unstable, ultraviolet light quickly breaks it up, and the process begins again.
Ozone in the Troposphere:
The other 10% of the ozone in the earth’s atmosphere is found in the troposphere, which is the portion of the atmosphere from the earth’s surface to about 12 km or 7 miles up. In the troposphere, Ozone is not wanted. Ozone is even more scarce in the troposphere than the stratosphere with concentration of about 0.02 to 0.3 parts per million. But even in such small doses, this molecule can do a lot of damage.
And just to confuse things even further, Ozone in the troposphere is one of the green-house gases. As discussed in the Green-house Effect section, the naturally occurring green-house gases (including Ozone) are what make earth habitable for life as we know it.
But scientists are very much concerned about the warming effects of increased green-house gases caused by human activity. So, in the troposphere, accelerated Ozone levels deal us a double whammy — as a key ingredient in smog and as a powerful green-house gas.
Project Report # 5. Green-House Effect and Carbon Dioxide:
Over the several billion years of geologic history, the quantity of carbon dioxide found in the atmosphere has been steadily decreasing. Researches theorized that this change is in response to an increase in the Sun’s output over the same time period. Higher levels of carbon dioxide help in regulating the Earth’s temperature to levels slightly higher than what is perceived today.
There moderate temperatures allowed the flourishing of plant life despite the lower output of solar radiation. An enhanced green-house effect, due to the greater concentration of carbon dioxide gas in the atmosphere, supplemented the production of heat energy through higher levels of long-wave counter-radiation.
As the sun grew more intense, several biological mechanisms gradually locked some of the atmospheric carbon dioxide into fossil fuels and sedimentary rocks.
All life is based on the element carbon. Carbon is the major chemical constituent of most organic matter, from fossil fuels to the complex molecules (DNA and RNA) that control genetic reproduction in organisms. Yet by weight, carbon is not one of the most abundant elements within the Earth’s crust.
In fact, the lithosphere is only 0.032% carbon by weight. In comparison, oxygen and silicon respectively make up 45.2% and 29.4% of the Earth’s surface rocks.
Carbon is stored on our planet in the following major sources:
(1) as organic molecules in living and dead organisms found in the biosphere;
(2) as the gas carbon dioxide in the atmosphere;
(3) as organic matter in soils;
(4) in the lithosphere as fossil fuels and sedimentary rock deposits such as limestone, dolomite and chalk; and
(5) in the oceans as dissolved atmospheric carbon dioxide and as calcium carbonate shells in marine organisms.
Ecosystems gain most of their carbon dioxide from the atmosphere. A number of autotrophic organisms have specialized mechanisms that allow for absorption of this gas into their cells. With the addition of water and energy from solar radiation, these organisms use carbon dioxide to chemical conversion in carbon- based sugar molecules by photosynthesis.
These molecules can then be chemically modified by these organisms through the metabolic addition of other elements to produce more complex compounds like proteins, cellulose, and amino acids. Some of the organic matter produced in plants is passed down to heterotrophic animals through consumption.
Carbon dioxide enters the waters of the ocean by simple diffusion. Once dissolved in seawater, the carbon dioxide can remain as is or can be converted into carbonate (CO3‑2) or bicarbonate (HCO3-) certain forms of sea life biologically fix bicarbonate with calcium (Ca+2) to produce calcium carbonate (CaCO3). This substance is used to produce shells and other body parts by organisms such as coral, clams, oysters, some protozoa, and some algae.
When these organisms die, their shells and body parts sink to the ocean floor where they accumulate as carbonate-rich deposits. After long periods of time, these deposits are physically and chemically altered into sedimentary rocks. Ocean deposits are by far the biggest sink of carbon on the planet (Table 2).
Carbon is released from ecosystems as carbon dioxide gas by the process of respiration. Respiration takes place in both plants and animals and involves the breakdown of carbon-based organic molecules into carbon dioxide gas and some other compound by products. The detritus food chain contains a number of organisms whose primary ecological role is the decomposition of organic matter into its biotic components.
Carbon is stored in the lithosphere in both inorganic and organic forms, Inorganic deposits of carbon in the lithosphere include fossil fuels like coal, oil, and shale and carbonate based sedimentary deposits like limestone. Organic forms of carbon in the lithosphere include litter, organic matter, and humic substances found in soils.
Some carbon dioxide is released from the interior of the lithosphere by-volcanoes. Carbon dioxide released by volcanoes enters the lower lithosphere when carbon-rich sediments and sedimentary rocks are sub ducted and partially melted beneath tectonic boundary zones.
Sine the Industrial Revolution, human beings has greatly increased the quantity of carbon dioxide found in the Earth’s atmosphere and oceans. Atmospheric levels have increased by over 30%, from about 275 parts per million (ppm) in the early 1700s to just over 365 PPM today.
Scientists estimate that future atmospheric levels of carbon dioxide could reach an amount between 450 to 600 PPM by the year 2100. The major sources of this gas due to human activities include fossil fuel combustion and the modification of natural plant cover found in grassland, woodland, and forested ecosystems.
Emissions from fossil fuel combustion account for about 65% of the additional carbon dioxide currently found in the atmosphere. The other 35% is derived from deforestation and the conversion of natural ecosystem into agricultural systems. Researchers have shown that natural ecosystem can store between 20 to 100 times more carbon dioxide than agricultural land-use types.
Carbon Dioxide:
Carbon dioxide, a chemical compound, that constitutes of two atoms of oxygen, covalently bonded to a single atom of carbon, turns into a gas at standard temperature and pressure. The chemical formula for carbon dioxide is CO2. Carbon dioxide is produced in several processes, prominent one being respiration in plants and animals (including human beings) and combustion of fossil fuels.
Carbon dioxide in small amounts is also produced in several geothermal processes, such as eruption of a volcano. Recent estimates reveal that the concentration of carbon dioxide in the Earth’s atmosphere has increased to 387 parts per million green-house gases.
Since the beginning of the Industrial revolution, the burning of fossil fuels has contributed to the increase in carbon dioxide in the atmosphere from 280 ppm to 390 ppm, despite the uptake of a large portion of the emission through various natural “sink” involved it the carbon cycle.
Unlike other gases, carbon dioxide emissions do not result from inefficient combustion:
CO2 is a product of ideal, stoichiometric combustion of carbon. At present, the emissions of carbon are directly proportional to fossil-fuel based energy consumption. Some 2000 fossil fuel related carbon emissions have equaled or exceeded the IPCC.
Strengthening of the green-house effect through human activities is known as anthropogenic green-house effect. This increase in radiative forcing from human activities is attributable mainly to increased atmospheric carbon dioxide levels.
CO2 is produced by fossil fuel burning and other activities such as cement production and tropical deforestation. Measurements of CO2 show that concentration has increased from about 313 ppm in 1960 to about 389 ppm in 2010.
The current observed amount of CO2 exceeds the geological record maxima (□ 300ppm) from ice core data. The effect of combustion produced by carbon dioxide on the global climate is called the calendar effect. It was first described in 1896 by Svante Arrhenius.
Elevated CO2 levels contribute to additional absorption and emission of thermal infrared in the atmosphere which produce net warming. According to the latest Assessment Report from the Intergovernmental Panel on Climate Change, “most of the observed increase in globally averaged temperatures since the mid- 20th century is very likely due to the observed increase in anthropogenic green-house gas concentrations”.
Over the past 800,000 years ice core data shows that carbon dioxide has varied from values as low as 180 parts per million (ppm) to the pre-industrial level of 270 ppm.
The proportion of an emission (e.g. CO2 Remaining in the atmosphere after a specified time is the “Airborne Fraction”. More precisely, the annual AF is the ratio of the atmospheric CO2 increase in a given year to the year’s total emission, and calculates that of the average 9.1 PgC y-1 of total anthropogenic emissions from 2000 to 2006, the AF as 0.45. For CO2 the AF over the last 50 years (1956- 2006) has been increasing at 0.25 ± 0.21% per year.
Carbon monoxide has an indirect radiative effect by elevating concentrations of methane and tropospheric ozone through scavenging of atmospheric constituents (e.g., the hydroxyl radical, OH) that would otherwise destroy them Carbon monoxide is created when carbon-containing fuels are burnt incompletely.
Through natural process in the atmosphere, it is eventually oxidized to carbon dioxide. Carbon monoxide has an atmospheric lifetime of only a few months and as a consequence is spatially more variable than longer-lived gases.
Green-House Effect and Global Warming:
Green-house effect is necessary for survival of life on Earth. But the excess buildup of the green-house gases in the atmosphere is a cause of worry. This is due to industries and vehicles giving out these gases at an alarmingly high rate.
The result is that more amount of heat is being trapped and sent back to the Earth by the green-house gases. Due to this, the temperature of the Earth is rising which is termed as global warming on Earth includes melting of the polar ice, rising level of water in seas and oceans and all this adversely affects plant and animal life on the Earth.
Although a natural and a necessary phenomenon, rapid industrialization is adding to the green-house gases at an alarmingly high rate and that is the reason that it has become a matter of concern and a topic of debate in every environmental meet.
Green-House Gases Reached Record High in 2005:
The data gathered by the weather agency, which is part of the United Nations, showed that the global average concentrations of carbon dioxide (CO2) and nitrous oxide (N2O) were higher in the year 2005 than ever before. The concentration of CO2 rose by about 0.5% to reach 397.1 parts per million, according to the agency. N2O rose by about 0.19% since 2004, to total 319.2 parts per million.
The WMO said that there is no sign that N2O and CO2 are starting to level off. “Levels of methane, another green-house gas, remained stable since 2005 power plants, automobiles, airplanes, and ships using coal, oil or gas, are contributing to the rise in carbon dioxide emissions. The WMO’s statement revealed that there is 35.4% more carbon dioxide in the atmosphere since the late 18th century primarily because of human burning fossil fuels.
The gases released by fossil fuel-burning reappear in the atmosphere, and as a result it also has concluded that “green-house gases are some of the major drivers behind global warming and climate change.”
A report by the British government warned that global warming could devastate the world economy as badly as it was damaged during the world wars and the Great Depression, if it is left unchecked.
The report said that warming could melt glaciers, raise sea levels, cause crop yields to decline, and cause higher death tolls from heat strokes, with widespread outbreaks of malaria and dengue fever. Developing countries would be the hardest hit.
Project Report # 6. Green-House Effect and Methane:
Another prominent gas featuring in the green-house gases list is methane. The molecular formula of methane is CH4. It is one of the most potent green-house gases with a global warming potential of 25 averaged over a century. It absorbs radiation in the wavelength range from 3 to 4 µm and 7 to 8.4 µm.
The capacity of methane to trap heat is 20 times more than that of carbon dioxide. This gas is produced in large amount during a process known as methanogenesis. It is found that the Earth’s crust contains huge deposits of methane gas, a part of which is let out in the process of mining, thus adding to the green-house effect.
It is found that the amount of methane in the atmosphere has gone up from 700 parts per billion in 1750 to 1745 parts per billion in 1998, which constitutes 4 to 9 percent of green-house gases.
Methane is essential for microbial fermentation a reaction that is released from certain environments. The primary for methane can be described as wetlands. Methane is known to be released by such environment as coal mines, and oil wells.
Thus, methane is released in many industrial areas. Methane is also thought to be generated in the stomachs of certain animals, and methane is responsible for the rise in the gas that has been appearing in the troposphere.
Methane tends to be gradually broken down in reaction with other gases in the earth’s atmosphere. In recent years it has been noted that methane is being added to the environment faster than broken down, thus contributing to global warming. It is estimated that the amount of methane has doubled since the onset of the Industrial Revolution.
Methane (CH4) is a very simple molecule (one carbon surrounded by four hydrogen atoms) and is created predominantly by bacteria that feed on organic material. In wet areas such as swamps, wetlands and in the oceans, there is not enough oxygen, and so complex hydrocarbons get broken down to methane by anaerobic bacteria. Some of this methane can get trapped (as a gas, as a solid, dissolved or eaten) and some makes its way to the atmosphere where it is gradually broken down to CO2 and water (H2O) vapour in a series of chemical reactions.
Although methane was detected in the atmosphere in 1948, its importance to climate was only recently revealed. Methane in the atmosphere was actually a significantly green-house gas – it absorbs some frequencies of infrared radiation (emitted from the Earth’s surface) that would otherwise go straight out to space.
In combination with other green-house gases (water vapour, CO2 and N2O), this leads to a surface temperature that is about 30°C warmer than if there were no atmosphere.
The second result was due to the recovery and analysis of Greenland and Antarctic ice cores. These multi-kilometer cores, drilled through the ice sheets have shown in unprecedented detail climate changes over centuries, millennia, and hundreds of thousands of years.
Indeed, annual layers can be discerned for much of the length of the cores, which allowed researchers to construct an extremely accurate timescale for the climate-related changes they found.
The gases trapped inside tiny bubbles in the ice are isolated as CO2 and CH4 within those bubbles showed that since the industrial period began (around the mid-1800s) concentrations of both CO2 and CH4 have been increasing rapidly.
In fact, CH4 concentrations have more than doubled over the last 150 years, and the contribution to the enhanced green-house effect is almost half of that due to CO2 increase over the sample period.
The changes over the last century seem to be mostly related to increased emissions due to human activity: leaks from mining and natural gas pipelines, increased irrigation (particularly rice pady, among other factors.
Methane and Climate:
In the lower part of the atmosphere, below about 10-12 km (the troposphere), the key cycles are mediated above all by the presence of , what are called OH radicals – colloquially known as the atmospheric detergent. All hydrocarbons (e.g. methane) chemical species that are emitted can be eventually broken down (or oxidized) by these radicals to CO2 and H2O.
An average molecule of CH4 lasts around eight to nine years before it gets oxidized. This a long time compared to most atmospheric chemicals but is fast enough so that there can be significant year-to-year variability. Around 10% of the CH4 makes it into the upper atmosphere (the stratosphere, between 15 and 50 km above sea level) where it also gets oxidized, though through a slightly different set of reactions.
A key point is that in the very dry stratosphere, the water produced from methane oxidation is a big part of the water budget and stratospheric water vapor is a green-house gas in its own right! This indirect process enhances the climate impact of methane changes by about 15%.
Methane is introduced in the environment through the cycle known as Methanogenesis or biomethanation.
Methanogenesis and Green-house Effect:
Methane is both a potential alternate energy source and a potent green-house gas. Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emission also results from the decomposition of organic wastes in municipal solids, water, landfills and livestock, mostly cows. Methanogenic bacteria in the ruminant digestive tract are a major cause of this gas.
Each green-house gas differs in its ability to absorb heat in the atmosphere. Methane traps over 21 times more heat per molecule than carbon dioxide and is expected to cause between 15 and 17% of the global warming over the next 50 years.
Role of Ruminants in Methane Production:
According to a report of NBRI the Heat Radiation Balance of the Earth, the livestock and associated manure management also contribute about 16% of total annual production of methane. These emissions are the direct result of digestion of fibrous grasses in the rumen of the animals.
Cows account for about 80% of the global annual CH4 emission from domestic livestock. This would mean that cows account for 12.8% of the total annual production of methane. Methane (CH4) is released by livestock as a by-product of digestion. The breakdown of carbohydrates in the digestive tract of herbivores (including insects and human beings) result in the production of methane.
The initial steps are performed either by facultative anaerobic bacteria such as E. coli which convert format to H2 and CO2 or by obligate anaerobes like Clostridium or Selenomas which also do similar conversions Methanogenic archae bacteria (a group separate from true bacteria) are obligate anaerobes that are very sensitive to oxygen and prefer environments without any other electron acceptors such as nitrogen.
They perform the final steps in the fermentation and they convert approximately 90-95% H2 and CO2 produced by the other organisms of methane or they can convert acetic acid to methane. The energy derived is used to fix the remaining CO2 into cellular materials.
These methanogens are present in ruminants other than cows, such as sheep and wilde beast. Approximately, 10 percent of human beings have these methanogens in their guts as well, probably inherited from their parents.
It has been estimated that 9 to 12% of the energy that a cow consumes is turned to methane. A cow in a barn produces 542 liters of methane a day and 600 liters when out in a field.
The livestock and associated manure management also contribute about 16% of total annual production of methane. These emissions are the direct result of digestion of fibrous grasses in the rumen of the animals. Cows account for about 80% of the global annual CH4 emissions from domestic livestock. This would mean that cows account for 12.8% of the total annual production of methane.
Project Report # 7. List of Green-House Gases in the Atmosphere:
Going through this table will provide you a better picture about the various gases & constituents of green-house effect.
