notesblognepal.blogspot.com
1. Answer the following questionsnotesblognepal.blogspot.com
a. What is a
greenhouse? What is its specific characteristics?notesblognepal.blogspot.com
Answer: - Greenhouse is a house made up of glass or
plastic, especially constructed to grow plants by maintaining proper temperature
inside it. It allows the radiation of sun to pass in but the reflected rays can
not escape away from within the house. By such process there is the condition,
where the heat get trapped and the temperature is more than in the surrounding.
In other words the wall of greenhouse keeps warmer inside it by trapping
infrared radiation. (A greenhouse is a form of controlled environment
agriculture because the temperature, light, moisture, soil and other conditions
essential for plants' growth can be regulated)
b. What is a
greenhouse effect? Name the factors that are mainly responsible to cause the greenhouse effect.notesblognepal.blogspot.com
Answer:
- It is the process by which absorption of infrared radiation by
atmospheric gases warms a planet's atmosphere and surface. The major factor
responsible for the greenhouse effects are; carbon dioxide, methane, nitrous
oxide, water vapour coming from the natural sources and some artificial
sources. The atmospheric concentration of CO2 and CH4
have increased by 31% and 149% respectively above pre-industrial level since
1750. These gases are mostly produced from the thermal plants in industries,
burning of carbonic fuels in vehicles, industries and residential areas and big
laboratories. The concentration of CO2 has also increased because of
the rapid destruction of forest area by the explosion of population.
The gaseous blanket around the globe maintains the
earth's temperature by absorbing infrared radiation and re-radiating solar
energy to the earth's surface. It is a natural process. However, the
concentration of greenhouse gases namely carbon dioxide, chlorofluorocarbons,
methane, nitrous oxides, ozone, etc. introduced into atmosphere by human
activities trap more heat and enhance the greenhouse effect resulting to the
global warming. As burning of fossil fuel, intensive agriculture, use of
chemicals like CFCs, industrial production, etc/ accumulate the greenhouse
gases into the atmosphere. These insulate the earth surface from the outer
space and traps more heat and re-radiates it to the earth's surface and global
warming occurs. Hence the human activities are mainly responsible for the
occurrence of the greenhouse effect.
c.
Describe any two natural greenhouse gases.notesblognepal.blogspot.com
Answer:
- The major natural greenhouse gases are water vapour, carbon dioxide,
methane and nitrous oxide. Among them two are described below.
Carbon dioxide (CO2) is
the primary greenhouse gas emitted through human activities. Carbon dioxide is naturally
present in the atmosphere as part of the Earth's carbon cycle (the natural
circulation of carbon among the atmosphere, oceans, soil, plants, and animals).
Human activities are altering the carbon cycle—both by adding more CO2 to the atmosphere and by influencing
the ability of natural sinks, like forests, to remove CO2 from the atmosphere. While CO2 emissions come from a variety of
natural sources, human-related emissions are responsible for the increase that
has occurred in the atmosphere since the industrial revolution.
Nitrous
Oxide: There are several oxides of
nitrogen present in the atmosphere. Among them nitrous oxide, nitric oxide and
nitrogen dioxide are major air pollutants. However, greenhouse effect is caused
by nitrous oxide. It is also released from the burning of fossil fuels, organic
matter, microbial activity, chemical fertilizers, and from the agriculture
fields. It contributes 6% of the total greenhouse effect.
d. What is global warming? Mention any two causes of
global warming.
Answer: - The gradual
increase in the overall temperature of the earth atmosphere due to the
greenhouse effect caused by pollutants is called global warming. It is the
observed increase in the average temperature of the Earth's near-surface air
and oceans in recent decades and its projected continuation. Global average
temperature near Earth's surface raised 0.74
+/- 0.180C during the last century. The major causes behind
the increase in the global warming are detailed below.
Addition of CO2 or CH4 in the
atmosphere than the natural composition increases the possibilities of
greenhouse effects, which in turn make the planet's surface warmer. The
increased CO2 in the atmosphere warms the atmosphere Earth's surface
and leads to melting of ice near the poles. As the ice melts, land or open
water takes its place; both land and open water are in average less reflective
than ice, and thus absorb more solar radiation. This causes more warming of the
planet. The other cause of global warming is destruction of ozone layer. When
the ozone layer gets destroyed, the harmful radiation of sun having more
capacity of heating enters the Earth's surface, which results to increase in
temperature of Earth.
Answer:
- An increase in global temperatures can in turn cause other changes
including sea level rise, and changes in the amount of precipitation. It
increases the rate of melting of polar ice, mountain snow and the glaciers as a
result the volume of water in the sea becomes more and the sea level rises up,
flooding in many coastal areas as an immediate effect on the other hand
increase in temperature increases the rate of evaporation which in turn brings
more harsh and heavy rainfall, which can be disaster for the civilization on
earth. There may also be increase in the frequency and intensity of extreme
weather events . It may affect in the production of crops and destroys the
fertility of soil. As the warm climate starts to climb up the diseases seen in
the warmer belts have started to be seen in the higher altitudes also. Global
warming is also related to the climatic shift. Scientist claim that the global
warming can lead to the next ice age also.
Answer: - The most
clearly observed effect of greenhouse gases is global warming. When the
concentration of greenhouse gases increase in the atmosphere it increases the
rate of trapping the radiation of sunlight and this it increases the
temperature of the earth, which is termed as global warming. The second effects
seen by the collection of greenhouse gases is depletion of ozone layer. The
gases which are responsible for the greenhouse effect may find their way to the
stratosphere where they chemically or catalytically combine with the ozone
molecule and break it down to another form, mostly into oxygen gas. Last not
least, it is also responsible to bring the change of climatic pattern of the
world. The climate of the world is dependent upon the direction of wind and
direction of ocean current. Melting of polar ice is shutting down the natural
flow of water in ocean and in many places climatic extremes are being seen.
Increase in the rate of rainfall in some places and some places are
experiencing dry climate. The rate of natural disaster has also increased a lot
in the last decades which also clarifies the role of greenhouse gases in
climatic pattern.
Impacts of
greenhouse effects can be shown in the figure below in brief.notesblognepal.blogspot.com
g. Mention any
three measures for controlling greenhouse gases.notesblognepal.blogspot.com
Answer: - Reduction in emission of greenhouse gases:
This goal is only achieved when the burning of fossil fuels will be controlled.
The fossil fuels are the major source of greenhouse gases. Instead of fossil
fuels the alternative source of energy should be used like, solar energy, wind
energy, hydroelectricity, etc.
Source
control: The industries, factories or
any other agency, should use the technology that can reduce the emission of
green house to the atmosphere. The process of treatment, purification and
absorption should be carried out before releasing the greenhouse gases into the
atmosphere.
Planting
trees: Greenhouse gases especially
carbon dioxide is the resource for plants. They use carbon dioxide as raw material
during photosynthesis. So forestation and reforestation programmes should be
conducted and existing forestland should
be conserved.
Public
awareness: Public people should be
made aware about the adverse impact of greenhouse gases and global warming.
Local level programs should be launched in order to reduce greenhouse gases in
local level. They should be encouraged to use alternative energy sources and
government should provide subsidy to the people.
Legislation: The country should make legal provisions to control
emissions of greenhouse gases within the country. The polluters pays principle
should be implemented legally. As it is a global concern the international
community also should play important role in increasing the international
co-operation in this field.
h. Mention what efforts have been made worldwide for the
reduction of greenhouse gases.
Answer: - Various
programs are being launched by the global community for the reduction of
greenhouse gases; some of them are given below.
· The UN framework convention on climate change
established at Rio in 1992 asked the signatory
nations, especially developed countries to reduce their greenhouse gaseous
emissions in a year 2000 that would be equal to or below 1990 emissions.
· Various international agencies are working in the
reduction of greenhouse gases. UNEP is also working in the reduction of
greenhouse gases after its establishment in 1972. It does the constant close
watch of the environment through the program known as Earth-watch, it helps in
the adoption of environmentally sound policies.
· In 1988 intergovernmental panel on climate change was
established. It worked on methods of reducing impacts of global warming and
tried to sought out ways to cope with such changes.
· In 1992 the UNO organized an international conference
called world summit conference in Rio de Janerio. It is the grandest world
conference ever held in the history of mankind.
i. "One of the major consequences of global warming
is the
rise in sea
level". Clarify this statement.
Answer: - Global warming
brings various biological and physical hazards in on the face of planet. When
the global temperature increases it increases the rate of melting of snow of
the mountain, ice of the glacier and the snow lying in the both poles. Melting of
ice increases the volume of water in the water sources increases which in turn
mix in ocean. This process increases the deposit of water in ocean,
consequently the global sea level gradually rises up, which in other words is
the rise in the sea level.
j. In what way does the expansion of forest area help to
control the green house gases?
Answer: - Forest is a large extension of many types of vegetation.
It is the vegetation that helps to balance the level of CO2 and O2
in the atmosphere. Plants convert the harmful gas CO2 into useful
oxygen, which is known as carbon cycle. They use carbon dioxide as raw
materials during photosynthesis. On the other hand forest also protects water
resources. Water resources helps in the absorption of a certain amount of carbon
dioxide, which helps in reducing the concentration of greenhouse gases in the
atmosphere. It also maintains the ecological balances and helps to reduce the
over evolved carbon dioxide. Plants around the city area are useful in
reduction of the pollution created in the urban areas.
ii. Write a
short notes on:
1.Greenhouse gas:
Answer: - there are
numbers of greenhouse gases, some having natural sources and some are produced
from various artificial sources. The primary greenhouse gases are water vapor,
carbon dioxide and methane. Water is the most abundant in the atmosphere by
concentration, but it is a short term greenhouse gas and in a dynamic
equilibrium in the atmosphere. Great quantities of water can be added to the
atmosphere by evaporation or subtracted by precipitation in a period of weeks.
Methane is an intermediate term greenhouse gas and in the atmosphere it is
converted to another form in a period of months to year. CO2 is a
long term greenhouse gas and, once added to the atmosphere can remain in the
atmosphere for hundreds of years. Some of the most potent greenhouse gases are
produced solely by human activities. Fluorinated compounds such as CFCs, HCFCs
and HFCs are thousands time effective in trapping heat than a single molecule
of CO2. Compound like trifluoromethyl sulphur pentafluoride,
unreported earlier are also found to be responsible for greenhouse effects.
2.Water vapour as a green house gas:
Answer: - It is the most
common greenhouse gas. It contributes 60-70% of the total greenhouse effects.
Along with the increase in the human activities the concentration of other
gases increases in the atmosphere which accelerates the rate of evaporation
from the various sources of water and plants
that ultimately increases the amount of water vapour in the atmosphere.
Though water is the most abundant in the atmosphere by concentration, but it is
a short term greenhouse gas and in a dynamic equilibrium in the atmosphere.
Great quantities of water can be added to the atmosphere by evaporation or subtracted
by precipitation in a period of weeks.
3.Climate change due to volcanic eruptions.
Answer: - Volcano is a
natural calamity. A volcano is a place through which molten rocks and gases
escape into the surface of the earth or in the atmosphere. After the volcanic
eruptions various gases and dust particles spreads in the atmosphere. These
substances can spread in the atmosphere and act like a blanket. A massive
volcano usually termed as super volcano can
shoot millions tons of sulphur dioxide and other various greenhouse gases in
the atmosphere. A thick cloud envelops the earth surface and the sunlight can
not pass through this layer, which results to rapid decline in the temperature
of the earth surface which is known as volcanic
winter which can remain for several months or years. Many scientists
believe the pre-human global warming and climate shift was the product of some
natural process including the volcanoes occurring on the earth surface. The
1991 eruption of Mt Pinatubo in the Philippines affected the global
surface cooling by 0.50C a year after the eruption. The eruption of
Toba in Sumatra 73,500 years ago may have
cooled the planet by 3-50C, which also shows the impact of volcano
in causing the change in climate.
4.Greenhouse effect;
Answer: - It is the
process by which absorption of infrared radiation by atmospheric gases warms a
planet's atmosphere and surface. The greenhouse effect cause the atmosphere to
trap more heat energy at the earth's surface and with in the atmosphere by
absorbing and re-emitting lone wave energy. Of the long wave energy emitted
back to space, 90% is intercepted and absorbed by greenhouse gases. Without the
greenhouse effect, the earth's average global temperature would be -180
C rather than the present 150 C. in the last few centuries, the
activities of the human have directly or indirectly caused the concentration of
the major greenhouse gases to increase. Scientists predict that this increase
may enhance the greenhouse effect making the planet warmer. Some experts estimate
that the earths average global temperature has already increased by 0.3-0.60
C, since the beginning of this century, because of this enhancement. It is seen
as a major environmental hazard. Average increases in temperature could change
weather pattern and agricultural out put. It might lead to melting of the polar
ice caps and corresponding rise in sea level.
Answer: - The gradual
increase in the overall temperature of the earth's atmosphere due to the
greenhouse effect caused by pollutants is called global warming. In other words
warming of earth's average global temperature because of an increase in the
concentration of greenhouse gases. A greater concentration in greenhouse gases
in the atmosphere is believed to result in an enhancement of the greenhouse
effect and it in turn it increases the global temperature. Increase in global
temperature is a global issue and has brought symptoms of some major global
disaster. An increase in global temperature can in turn cause other changes,
including sea level rise, and changes in the amount of precipitation. It
increases the rate of melting of polar ice, mountain snow and the glaciers as a
result the volume of water in the sea become more ant the sea level rises up,
flooding in many coastal areas as an immediate effect on the other hand
increase in temperature increases the rate of evaporation which in turn brings
more harsh and heavy rainfall, which can be disaster for the living beings of
earth. There may also be increase in the frequency and intensity of extreme
weather events though it is difficult to connect specific events to global
warming. Other consequences may include changes in agricultural yields. Glacier
retreat, reduced summer stream flows, species extinction and increase in the
ranges of disease vectors.
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