Assignment on NS 3 Greenhouse Part 2

8/2/2019 Assignment on NS 3 Greenhouse Part 2

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Chapter Two: Greenhouse

2.1 What is Greenhouse?

A greenhouse (also called a glasshouse) is a building where plants are grown. A

greenhouse is a structure with a glass or plastic roof and frequently glass or plastic

walls; it heats up because incoming visible solar radiation from the sun is absorbed by

plants, soil, and other things inside the building. Glass is transparent to this radiation.

The warmed structures and plants inside the greenhouse re-radiate this energy in the

infra-red, to which glass is partly opaque, and that energy is trapped inside the

glasshouse. Although there is some heat loss due to conduction, there is a net increase

in energy (and therefore temperature) inside the greenhouse. Air warmed by the heat

from hot interior surfaces is retained in the building by the roof and wall. These

structures range in size from small sheds to very large buildings.

2.2 History of Greenhouse

19th Century Orangerie in Weilburg, Germany. The idea of growing plants in

environmentally controlled areas has existed since Roman times. The Roman emperor

Tiberius ate a cucumber-like vegetable daily. The Roman gardeners used artificial

methods (similar to the greenhouse system) of growing to have it available for his table

every day of the year. Cucumbers were planted in wheeled carts which were put in the

sun daily, and then taken inside to keep them warm at night. The cucumbers were

stored under frames or in cucumber houses glazed with either oiled cloth known as

"specularia" or with sheets of serenity (a.k.a. lapis specularis), according to the

description by Pliny the Elder.

The first modern greenhouses were built in Italy in the thirteenth century to house the

exotic plants that explorers brought back from the tropics. They were originally calledgiardini botanici (botanical gardens). The concept of greenhouses soon spread to the

Netherlands and then England, along with the plants. Some of these early attempts

required enormous amounts of work to close up at night or to winterize. There were

serious problems with providing adequate and balanced heat in these early greenhouses.

Today the Netherlands as many of the largest greenhouses in the world, some of them

so vast that they are able to produce millions of vegetables every year.

The French botanist Charles Lucien Bonaparte is often credited with building the first

practical modern greenhouse in Lei den, Holland to grow medicinal tropical plants.

In Japan, the first greenhouse was built in 1880 by Samuel Cocking, a British merchant

who exported herbs.

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In the Twentieth Century the geodesic dome was added to the many types of

greenhouses. A notable example is the Eden Project, in Cornwall.

2.3 Uses of Greenhouse

Greenhouses protect crops from too much heat or cold, shield plants from dust

storms and blizzards, and help to keep out pests. Light and temperature control

allows greenhouses to turn inerrable land into arable land, thereby improving

food production in marginal environments.

Because greenhouses allow certain crops to be grown throughout the year,

greenhouses are increasingly important in the food supply of high latitude

countries. One of the largest greenhouse complexes in the world is in Almeria,

Spain, where greenhouses cover almost 50,000 acres (200 km2). Sometimes

called the sea of plastics.

Greenhouses are often used for growing flowers,vegetables, fruits, and tobacco

plants. Bumblebees are the pollinators of choice for most greenhouse

pollination, although other types ofbees have been used, as well as artificial

pollination. Hydroponics can be used in greenhouses as well to make the most

use of the interior space.

Besides tobacco, many vegetables and flowers are grown in greenhouses in late

winter and early spring, and then transplanted outside as the weather warms.

Started plants are usually available for gardeners in farmers' markets at

transplanting time. Special greenhouse varieties of certain crops such as

tomatoes are generally used for commercial production.

The closed environment of a greenhouse has its own unique requirements,

compared with outdoor production. Pests and diseases, and extremes of heat and

humidity, have to be controlled, and irrigation is necessary to provide water.

Significant inputs of heat and light may be required, particularly with winter

production of warm-weather vegetables.

Because the temperature and humidity of greenhouses must be constantly

monitored to ensure optimal conditions, a wireless sensor networkcan be used

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to gather data remotely. The data is transmitted to a control location and used to

control heating, cooling, and irrigation systems.

2.4 Greenhouse Gases

By their percentage contribution to the greenhouse effect the four major gases are:

carbon dioxide 56%

methane, 18%

CFCs -13%

ozone 7%

Nitrous Oxide 6%

The major non-gas contributor to the Earth's greenhouse effect, clouds, also absorb and

emit infrared radiation and thus have an effect on radioactive properties of the

atmosphere.

Figure: Green House Gases

Figure: CO2-emissions world-wide by year

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2.5 What is Greenhouse Effect?

A representation of the exchanges of energy between the source (the Sun), the Earth's

surface, the Earth's atmosphere, and the ultimate sink outer space. The ability of the

atmosphere to capture and recycle energy emitted by the Earth surface is the definingcharacteristic of the greenhouse effect.

Figure: Green House Effect

The greenhouse effect is a process by which radiative energy leaving a planetary

surface is absorbed by some atmospheric gases, called greenhouse gases. They transfer

this energy to other components of the atmosphere, and it is re-radiated in all directions,

including back down towards the surface. This transfers energy to the surface and lower

atmosphere, so the temperature there is higher than it would be if direct heating by solar

radiation were the only warming mechanism.

This mechanism is fundamentally different from that of an actual greenhouse, which

works by isolating warm air inside the structure so that heat is not lost by convection.The greenhouse effect was discovered by Joseph Fourier in 1824, first reliably

experimented on by John Tyndall in 1858, and first reported quantitatively by Svante

Arrhenius in 1896.

According to Business dictionary

Steady increase in the Earth's average lower atmosphere (near surface) temperature due

to heat retention caused by the accumulation of greenhouse gases (including water

vapor, carbon dioxide, methane, nitrous oxides, and chlorofluorocarbons or CFCs).

These gases form a blanket around the earth that lets the incoming sun rays (short wave

radiation) to pass through but block the reflected heat rays (long wave radiation) fromgoing out into the space.

According to Science

A term used to describe the heating of the atmosphere owing to the presence ofcarbon

dioxide and othergases. Without the presence of these gases, heat from the sun would

return to space in the form ofinfrared radiation. Carbon dioxide and other gases absorb

some of this radiation and prevent its release, thereby warming the Earth. This is an

effect analogous to what happens in a greenhouse, where glass traps the infrared

radiation and warms the air.

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If an ideal thermally conductiveblackbodywas the same distance from the Sun as the

Earth, it would have an expected blackbody temperature of 5.3 C. However, since the

Earth reflects about 30% (or 28%) of the incoming sunlight, the planet's actual

blackbody temperature is about -18 or -19 C, about 33C below the actual surface

temperature of about 14 C or 15 C. The mechanism that produces this difference

between the actual temperature and the blackbody temperature is due to the atmosphereand is known as the greenhouse effect.

2.6 The distinction between the greenhouse effect and real

greenhouses

The "greenhouse effect" is named by analogy to greenhouses but this is a

misnomer. The greenhouse effect and a real greenhouse are similar in that they

both limit the rate of thermal energy flowing out of the system, but the

mechanisms by which heat is retained are different. A greenhouse works

primarily by preventing absorbed heat from leaving the structure throughconvection, i.e. sensible heat transport. The greenhouse effect heats the earth

because greenhouse gases absorb outgoing radiative energy and re-emit some of

it back towards earth.

A greenhouse is built of any material that passes sunlight, usually glass, or

plastic. It mainly heats up because the Sun warms the ground inside, which then

warms the air in the greenhouse. The air continues to heat because it is confined

within the greenhouse, unlike the environment outside the greenhouse where

warm air near the surface rises and mixes with cooler air aloft. This can be

demonstrated by opening a small window near the roof of a greenhouse: the

temperature will drop considerably. It has also been demonstrated

experimentally that a "greenhouse" with a cover of rock salt (which is

transparent to infra red) heats up an enclosure similarly to one with a glass

cover. Thus greenhouses work primarily by preventing convective cooling.

In the greenhouse effect, rather than retaining (sensible) heat by physically

preventing movement of the air, greenhouse gases act to warm the Earth by re-

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radiating some of the energy back towards the surface. This process may exist

in real greenhouses, but is comparatively unimportant there.

2.7 Global Warming

Global warming is the increase in the average temperature ofEarth's near-surface air

and oceans since the mid-20th century and its projected continuation. According to the2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change

(IPCC), global surface temperature increased 0.74 0.18 C (1.33 0.32 F) during the

20th century. Most of the observed temperature increase since the middle of the 20th

century was caused by increasing concentrations of greenhouse gases, which results

from human activity such as fossil fuel burning and deforestation. Global dimming, a

result of increasing concentrations of atmospheric aerosols that block sunlight from

reaching the surface, has partially countered the effects of greenhouse gas induced

warming.

Climate model projections summarized in the latest IPCC report indicate that the global

surface temperature is likely to rise a further 1.1 to 6.4 C (2.0 to 11.5 F) during the

21st century. The uncertainty in this estimate arises from the use of models with

differing sensitivity to greenhouse gas concentrations and the use of differing estimates

of future greenhouse gas emissions.

An increase in global temperature will cause sea levels to rise and will change the

amount and pattern ofprecipitation, probably including expansion of subtropical

deserts. Warming is expected to be strongest in the Arctic and would be associated with

continuing retreat of glaciers, permafrost and sea ice. Other likely effects include

changes in the frequency and intensity of extreme weatherevents, species extinctions,

and changes in agricultural yields. Warming and related changes will vary from regionto region around the globe, though the nature of these regional variations is uncertain.

The scientific consensus is that anthropogenic global warming is occurring.

Nevertheless, political and public debate continues. The Kyoto Protocol is aimed at

stabilizing greenhouse gas concentration to prevent a "dangerous anthropogenic

interference". [9] As of November 2009, 187 states have signed and ratified the protocol.

2.8 Causes of Greenhouse Effect

The Greenhouse effect is a much debated issue. Here are some details about the causes

of the Greenhouse effect.

Humankind has progressed a lot over the years. However, this progress has come at a

cost of the exploitation of nature many a times. Humans are the main reason for the

pollution in nature.

Global warming has been a matter of concern for many years, with various man-made

machines now contributing to Global Warming.

One of the main causes of Global Warming is the Green house effect. When the

emission of infra-red radiation in the atmosphere warms a planet's surface, it is known

as the Green House Effect. The Greenhouse effect is a natural phenomena occurring onplanet Earth.

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The life on Earth depends entirely on the Sun. The energy for life is supplied by the

Sun. Out of the total sunlight available; more than thirty percent is deflected into outer

space. The rest is reflected and converted into slow moving energy called infrared

radiation. This radiation is then trapped into the atmosphere by various gases like

carbon-di-oxide, methane, ozone and water vapor. Therefore, its escape is slowed

down. Out of these gases, carbon-di-oxide itself is responsible for the Green houseeffect.

There are natural as well as human-made causes of the greenhouse effect. The natural

causes of the Green house effect are the emissions of gases like nitrous oxide, carbon-

di-oxide, methane, ozone and water vapor.

The greenhouse effect is actually beneficial to the Earth. It is only when human-made

processes increase its speed that the problems occur. One main problem is the oft

repeated 'Global Warming'.

One of the man-made causes of the Green House effect is deforestation. Deforestationincreases the amount of carbon-di-oxide in the atmosphere. Also, due to the

disappearance of trees, photosynthesis cannot take place. Deforestation causes of the

greenhouse effect. Deforestation is rampant today due to the increase in human

civilization. The levels of deforestation have increased by about nine percent in recent

times. Also, the burning of wood causes it to decay, therefore releasing more carbon-

dioxide into the atmosphere.

Greenhouse Gases also can be 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 Greenhouse Effect.

Other man-made causes of the increase in the Green house effect due to the emission of

such gases are any all electrical appliances. Even the humble refrigerator in the house

emits gases which contribute to the Greenhouse effect. These gases are known as

Chlorofluorocarbons (CFCs) and are used in refrigerators, aerosol cans, and some

foaming agents in the packaging industry, fire extinguisher chemicals and cleaners used

in the electronic industry. Some processes of the cement manufacturing industries also

act as a cause towards the Greenhouse effect.

Other man-made processes that contribute and are a cause to the Greenhouse effect are

burning of gasoline, oil and coal. Apart from these, some farming and land-useprocesses are 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 the global warming on the planet. These gases are not naturally

available in the atmosphere.

Population growth also is a indirect contributor and one of the causes of the Greenhouse

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 catalyze the green

house effect. The increase in population also results in the increase of agricultural

processes. Most man-made machines, like the automobile also contribute to the greenhouse effect.

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Humans Contribute in the Greenhouse Effect:

While the greenhouse effect is an essential environmental prerequisite for life on Earth,

there really can be too much of a good thing. The problems begin when humanactivities distort and accelerate the natural process by creating more greenhouse gases

in the atmosphere than are necessary to warm the planet to an ideal temperature.

Burning natural gas, coal and oil -including gasoline for automobile engines-

raises the level of carbon dioxide in the atmosphere.

Some farming practices and land-use changes increase the levels of methane

and nitrous oxide.

Many factories produce long-lasting industrial gases that do not occur naturally,

yet contribute significantly to the enhanced greenhouse effect and "global

warming" that is currently under way. Deforestation also contributes to global warming. Trees use carbon dioxide and

give off oxygen in its place, which helps to create the optimal balance of gases

in the atmosphere. As more forests are logged for timber or cut down to make

way for farming, however, there are fewer trees to perform this critical function.

Population growth is another factor in global warming, because as more people

use fossil fuels for heat, transportation and manufacturing the level of

greenhouse gases continues to increase. As more farming occurs to feed

millions of new people, more greenhouse gases enter the atmosphere.

2.9 Impacts of Greenhouse Effect

The greenhouse effect's impact is to make life as we know it possible on planet Earth,

but the greenhouse effect may also bring an end to life as we know it. The greenhouse

effect refers to the trapping of heat by certain gases in the atmosphere, including carbon

dioxide and methane. Although these gases occur in only trace amounts, they block

significant amounts of heat from escaping out into space, thus keeping the Earth warm

enough for us to survive. Humans have been adding greenhouse gases in excessive

amounts to the atmosphere ever since the Industrial Revolution, which is enhancing the

greenhouse effect and resulting in what is now known as global warming. This

increase in greenhouse gases has the potential to cause catastrophic problems for Earth

and its inhabitants.

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Droughts and Floods

Ironically, changes in the climate due to excess greenhouse gases are causing both

increased drought and increased flooding. Violent storm activity will increase as

temperatures rise and more water evaporates from the oceans. This includes more

powerful hurricanes, pacific typhoons, and an increased frequency of severe localizedstorms and tornadoes. As these storms often result in flooding and property damage,

insurance premiums are skyrocketing in coastal areas as insurance companies struggle

to cover escalating costs. Warming also causes faster evaporation on land. Many dry

areas, including the American West, Southern Africa, and Australia are experiencing

more severe droughts. The amount of land on the Earth suffering from drought

conditions has doubled since 1970. This has occurred even as total global rainfall has

increased by an estimated 10%!

Environmental Impact:

According the burning of fossil fuels (coal, oil, and natural gas) and the clearing of

land. Most of the burning occurs in automobiles, in factories, and in electric power

plants that provide energy for houses and office buildings. The burning of fossil fuels

creates carbon dioxide, whose chemical formula is CO2. CO2 is a greenhouse gas that

slows the escape of heat into space. Trees and other plants remove CO2 from the air

during photosynthesis, the process they use to produce food. The clearing of land

contributes to the buildup of CO2 by reducing the rate at which the gas is removed from

the atmosphere or by the decomposition of dead vegetation. Continued global warming

could have many damaging effects. It might harm Plants and animals that live in the

sea. It could also force animals and plants on land to move to new habitats. Weather

patterns could change, causing flooding, drought, and an increase in damaging storms.

Global warming could melt enough polar ice to raise the sea level. In certain parts of

the world, human diseases could spread, and crop yields could decline.

The Human Price of Climate Change

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Drought is driving current increases in food prices around the world, in combination

with increased use of grains for fuel. Globally, the number of malnourished people

decreased up until the late 1990s. Now that number is increasing. Disease carriers will

expand their territory, either by moving to higher elevations in mountainous areas or by

expanding their territory further from the equator. This expansion will expose millions

of humans to the often deadly infectious diseases that these animals transmit. 150,000annual deaths worldwide have been tied to climate change already, according to a 2005

World Health Organization report. Climate related deaths are expected to double in 25

years. Industrialized countries may be sheltered from the current impacts of climate

change, but others are not. Heat waves and droughts are responsible for these deaths, as

well as floods and more powerful storms linked to climate change.

The Biggest Problem - Sea Level Rise

The most dangerous aspect of global warming is probably sea level rise. In fact, the

world's oceans have already risen 4-8 inches. That may not sound like much, but it has

been enough to cause the erosion of some islands. People have had to relocate to higher

ground on low-lying islands in the South Pacific and off the coast of India as a result of

the effects of global warming. Further sea level rise could cause great suffering. In

Bangladesh alone, there are 15 million people living within 1 meter of sea level and

another 8 million in a similar circumstance in India. Inhabited land could be inundated

if sea levels continue to rise. Much of the world's best farmland is low-lying, as are

many of the world's largest cities. Even a very modest rise in sea levels would have an

enormous impact on Millions of people around the world.

Approaching a Slippery Slope

Global temperatures have risen about .8 Celsius or 1.4 Fahrenheit already. As a result

of this increase, the vast arctic tundra is melting, releasing enormous volumes of both

carbon dioxide and methane into the atmosphere. This creates the possibility of a self-

reinforcing loop of climate change: as more carbon dioxide and methane are released

from the arctic tundra, the greenhouse effect will be further enhanced. The world's

oceans are losing their ability to absorb carbon because of rising water temperatures,

according to accumulating evidence. This is significant because the world's oceans hold

50 times more carbon than do the world's forests and grasslands. The decreasing

capacity of the Earth's carbon sinks to absorb carbon could further increase thelikelihood of runaway climate change.

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Rapid Climate Shifts

Scientists are becoming convinced that past cycles of climate change on the Earth have

been anything but slow and incremental, ever since the idea that the Earth may warm

over time as a result of human-created climate change has reached the public

consciousness. Climate change happens suddenly and violently. Research indicates thatthe Earth's climate exists in a stable state for many thousands of years. Then, pressure

for change builds from increases or decreases in carbon levels as well as changes in

solar radiation. At some point, the Earth reaches a tipping point where global climate

systems and ocean currents are radically altered over the course of only a few years, or

even months. Once that threshold is crossed, the Earth's climate goes through a period

of dramatic disequilibrium, finally settling down in a new stable state that is very

different from the previous one. There is no turning back if we cross the threshold and

reach a tipping point. Weather patterns all over the world may be disrupted, ending life

as we know it. We must not gamble with all of life on Earth. You should work to take

decisive action to avoid devastating climate change.

Global warming and climate change

The terms 'global warming' and 'climate change' are often used interchangeably, but

there is a difference.

Global warming is the gradual increase of the Earths average surface

temperature, due to greenhouse gases in the atmosphere.

Climate change is a broader term. It refers to long-term changes in climate,

including average temperature and rainfall.

Impacts of climate change

Drought Climate change is one of the greatest social, economic and environmental

challenges of our time. Human activity is causing the climate to change. This, in turn, is

having an impact on Australia's rainfall, temperatures, bushfire frequency, health,

heritage and biodiversity for current and future generations. During the past 100 years,

global average surface temperature increased by about 0.7C. Since 1910 the average

temperature of Australia has risen by about 1C. Although these increases sound small,

they have a big impact on the world's climate.

Greenhouse effect in Agriculture:

Increase in soil water deficits i.e. dry soils become drier, therefore increased need forirrigation but: Could improve soil workability in wetter regions and diminish poaching

and erosion risk

The range of current crops will move northward

New crop varieties may need to be selected

Horticultural crops are more susceptible to changing conditions than arable

crops

Field vegetables will be particularly affected by temperature changes

Increase in disease transmission by faster growth rates of pathogens in the

environment and more efficient and abundant vectors Rate of evolution will increase in hotter, drier conditions and in extreme years.

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Temperature, rainfall projections

The projections for Australias climate make it clear that farmers and other Australians

should be prepared for a hotter, drier future. Changes in temperature, rainfall, and

extreme events will affect water availability, water and soil quality, fire risk, and theincidence of pests, weeds, and disease. Although these impacts will vary across

different agricultural activities and regions they may adversely affect crop yields,

pasture growth and livestock production, production costs and potentially lead to an

overall decrease in Australian agricultural productivity

Water

Anticipated declines across most agricultural areas are likely to affect rivers and dams

that supply most of the water used in Australian agriculture. Potential evaporation is

likely to increase and this, combined with expected reductions in rainfall, suggest up to

20 per cent more droughts could occur across Australia by 2030. For example, in theMurray Darling Basin (MDB), there is likely to be less water available in the future. By

2030 the median decline in flows for the MDB is projected to be 11 per cent 9 per cent

in the north and 13 per cent in the south.

Cropping and stone fruits

Grain yield and quality is likely to be affected by climate change in some parts of

Australia. Crops reliant on irrigation are likely to be threatened where irrigation water

availability is reduced. Australian temperate fruits are all likely to be negatively

affected by warmer conditions, especially if they require a winter chill to simulate fruit

production.

Livestock

Livestock systems are likely to be affected by climate through impacts on change in

feed production and grazing management, feed quality, exposure to heat and cold stress,

pest and disease impacts and increased soil erosion. For example, many livestock are

already subjected to periods of high heat stress, particularly in the northern part of

Australia. Increased heat stress on animals is expected as temperature and humidity

levels increase.

Health

Mental health issues are often heightened in the context of extreme climatic events such

as drought.

Increased water temperatures

It is projected that the greatest increase in sea surface temperature will occur off south-

east Australia. Summer sea surface temperature records already indicate an increase of

more than 1C since the 1940s off the east coast of Tasmania. Increases in sea surface

temperature are likely to affect the distribution of many species in the south-east and

offshore, with potential flow on effects to the broader marine ecosystem. The projected

increase in sea surface temperature may also have adverse impacts on the production of

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cool-water farmed aquaculture species, such as the salmon production industry in

Tasmania.

Changed flood frequency

Increases in extreme rainfall events are projected for many regions, although theimpacts are spatially variable. Increased extreme rainfall events are likely to result in

more flash flooding, strains on sewerage and drainage systems, and challenges for

emergency services.

Reduced water quality

Climate change is likely to increase the stress on rivers already under pressure from

salinity, over-allocation and declining water quality. Higher water temperatures and

reduced stream flows will adversely affect water quality affecting human uses and

environmental conditions. Drought conditions are likely to exacerbate erosion and

downstream sedimentation. Higher sediment loads enter rivers following extremerainfall events or extreme bushfire events, both of which are projected to increase with

climate change. Changed climatic conditions are also likely to produce conditions that

favor riparian and aquatic weeds and algal blooms.

Climate change in the future

Drought the impacts of human induced climate change will continue into the future. In

Australia, average temperature increases of 0.7 to 1.2C are likely by 2030 together

with changes in rainfall patterns and the frequency and/or intensity of extreme weather

events such as drought and severe storms. The Australian Government is working with

CSIRO and the Bureau of Meteorology to model future climate change scenarios.

Impact of future greenhouse effect on global vegetation and climate

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We use the fully coupled atmosphere-ocean-land model, FOAM-LPJ, to predict future

changes in global vegetation and climate due to continued rising levels of carbon

dioxide (CO2). In these simulations, we allow CO2 to transiently increase 1% per year

until reaching 4xCO2. We perform separate simulations to investigate the irradiative

(increased CO2 in the atmosphere leads to higher temperatures) and physiological

(increased CO2 in plants leads to greater photosynthesis) effects of rising CO2 and tocompare simulations with interactive and fixed vegetation cover. The model predicts

that in the future, tropical rainforests will suffer due to higher temperatures and reduced

rainfall while the boreal forests will continue to shift pole ward. The model simulates a

substantial heat stress on the boreal forest, which causes a vast loss of trees along the

southern portions of the modern boreal forest, although the likelihood of this vegetation

response remains uncertain. Vegetation feedbacks on the atmosphere are not substantial

on a global average but produce important regional effects, such as a reduced warming

trend over the areas of boreal tree loss in Eurasia.

Global Warming and the Earth's Water Cycle

Increases in anthropogenic greenhouse gases resulting from the burning of fossil fuels

and the deforestation of forests have altered the composition of the atmosphere,

resulting in an increase in the amount of heat energy trapped at or near the Earth's

surface. This enhancement of the greenhouse effect is increasing surface temperatures

while provoking other changes in climate as well. Both model results and observational

evidence indicate that roughly 80% of the net additional heat energy trapped at the

Earth's surface by the build-up of greenhouse gases is transferred back to the

atmosphere through increased evaporation of water from the land and ocean, where

condensation returns the additional heat to the atmosphere causing warming, while

enhancing precipitation. The remaining 20% of the net additional heat from theenhanced greenhouse effect contributes directly to warming of the surface and the

lower atmosphere. Both contributions lead to a general warming of the Earth's climate

and to an increase in the water vapor in the atmosphere (warming increases the

atmosphere's water-holding capacity), thereby further enhancing the greenhouse effect.

Thus, the trapped heat energy serves to accelerate the cycling of water (as water vapor)

from the surface to the atmosphere, and enhances the transfer of the water vapor back to

the surface as rain and snow (condensation and precipitation). The increased

availability of water vapor in the atmosphere also leads to a significant increase in the

energy available to drive storms and associated weather fronts, therefore affecting

rainfall rates, precipitation amounts, storm intensity, and related run.

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The Greenhouse Effect and the Carbon Cycle

Figure: A thicker blanket of greenhouse gases traps more infrared radiation and raises

temperatures

Life on earth is made possible by energy from the sun, which arrives mainly in the form

of visible light. About 30 per cent of sunlight is scattered back into space by the outer

atmosphere, but the rest reaches the earth's surface, which reflects it in the form of a

calmer, more slow-moving type of energy called infrared radiation. (This is the sort of

heat thrown off by an electric grill before the bars begin to grow red.) Infrared radiation

is carried slowly aloft by air currents, and its eventual escape into space is delayed by

greenhouse gases such as water vapor, carbon dioxide, ozone, and methane.

Greenhouse gases make up only about 1 per cent of the atmosphere, but

they act like a blanket around the earth, or like the glass roof of a greenhouse

-- they trap heat and keep the planet some 30 degrees C warmer than it would beotherwise.

Human activities are making the blanket "thicker" -- the natural levels of

these gases are being supplemented by emissions of carbon dioxide from the

burning of coal, oil, and natural gas; by additional methane and nitrous oxide

produced by farming activities and changes in land use; and by several long-

lived industrial gases that do not occur naturally.

These changes are happening at unprecedented speed. If emissions continue to

grow at current rates, it is almost certain that atmospheric levels of carbon

dioxide will double from pre-industrial levels during the 21st century. It is

possible they will triple.

The result, known as the "enhanced greenhouse effect," is a warming of theearth's surface and lower atmosphere. The IPCC assesses with very high

confidence that the globally averaged net effect of human activities since 1750

has been one of warming. The best case computer climate models estimate

that the average global temperature will rise by 1.8 C to 4.0 C by the year

2100. A temperature increase of 0.74 C occurred last century and for the next

two decades, a warming of about 0.2 C per decade is projected should

greenhouse gas emissions continue to rise at their current pace and are allowed

to double from their pre-industrial level.

A rise in temperature will be accompanied by changes in climate -- in such

things as cloud cover, precipitation, wind patterns, and the duration of seasons.

In its Fourth Assessment Report, the IPCC projects that heat waves and heavy

precipitation events are very likely to increase in frequency in the 21st century.

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In a world that is crowded and under stress, millions of people depend on

weather patterns, such as monsoon rains, to continue as they have in the past.

Changes, at a minimum, will be difficult and disruptive.

Figure: The Carbon Cycle

Carbon dioxide is responsible for over 60 per cent of the "enhanced greenhouse

effect." Humans are burning coal, oil, and natural gas at a rate that is much,

much faster than the speed at which these fossil fuels were created. This is

releasing the carbon stored in the fuels into the atmosphere and upsetting the

carbon cycle, the millennia-old, precisely balanced system by which carbon is

exchanged between the air, the oceans, and land vegetation. Currently,

atmospheric levels of carbon dioxide are rising by over 10 per cent every 20

years.

Climate change is inevitable because of past and current emissions. The

climate does not respond immediately to external changes, but after 150 years of

industrialization, global warming has momentum, and it will continue to affect

the earth's natural systems for hundreds of years even if greenhouse gas

emissions are reduced and atmospheric levels stop rising.

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Fossil fuel use is boosting atmospheric levels of carbon, upsetting an age-old balance.

Increasing Air Temperature

Increase in air temperature - popularly called as global warming - refers to meantemperature of entire globe averaged over all months and all places.

Figure: Global Air Temperature

Melting Of Ice Caps

The Arctic ice cap is floating; if it were to melt entirely there would be no change in sea

levels. However, Antarctica is a continent, a land mass, it isnt floating and any melting

here adds to the sea level as does melting of ice sheets and glaciers in places such as

Greenland.

Desertification

Shifting weather patterns mean some areas receive less rainfall; the ground becomes

barren and unable to sustain crops. In many parts of the world the layer of topsoil is

both very thin and very poor. The dry, dusty soil is readily blown away and the area

becomes desert. African and Asian countries are particularly hard hit.

2.10 Advantages and Disadvantages of Greenhouse Effect

2.10.1 Advantages of Greenhouse Effect

Arctic, Antarctic, Siberia, and other frozen regions of earth may experience

more plant growth and milder climates.

The next ice age may be prevented from occurring.

Northwest Passage through Canada's formerly-icy north opens up to sea

transportation.

Less need for energy consumption to warm cold places.

Fewer deaths or injuries due to cold weather.

Longer growing seasons could mean increased agricultural production in some

local areas.

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Mountains increase in height due to melting glaciers, becoming higher as they

rebound against the missing weight of the ice.

Boundary disputes between countries over low-lying islands will disappear.

2.10.2 Disadvantages of Green House Effect

Ocean circulation disrupted, disrupting and having unknown effects on world

climate.

Higher sea level leading to flooding of low-lying lands and deaths and disease

from flood and evacuation.

Deserts get drier leaving to increased desertification.

Changes to agricultural production that can lead to food shortages.

Water shortages in already water-scarce areas.

Starvation, malnutrition, and increased deaths due to food and crop shortages.

More extreme weather and an increased frequency of severe and catastrophic

storms.

Increased disease in humans and animals.

Increased deaths from heat waves.

Extinction of additional species of animals and plants.

Loss of animal and plant habitats.

Increased emigration of those from poorer or low-lying countries to wealthier or

higher countries seeking better (or non-deadly) conditions.

Additional use of energy resources for cooling needs.

Increased air pollution.

Increased allergy and asthma rates due to earlier blooming of plants.

Melt of permafrost leads to destruction of structures, landslides, and avalanches.

Permanent loss of glaciers and ice sheets.

Cultural or heritage sites destroyed faster due to increased extremes.

Increased acidity of rainfall.

Earlier drying of forests leading to increased forest fires in size and intensity.

Increased cost of insurance as insurers pay out more claims resulting from

increasingly large disasters.

Aggressiveness will increase, leading to an increase in the murder rate.

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Chapter Three: Conclusion & References

3.1 Conclusion

In conclusion we say that a greenhouse is a structure with a glass or plastic roof and

frequently glass or plastic walls; it heats up because incoming visible solar radiation

from the sun is absorbed by plants, soil, and other things inside the building.There aretwo meanings of the term "greenhouse effect". There is a "natural" greenhouse effect

that keeps the Earth's climate warm and habitable. There is also the "man-made"

greenhouse effect, which is the enhancement of Earth's natural greenhouse effect by the

addition of greenhouse gases from the burning of fossil fuels (mainly petroleum, coal,

and natural gas).

The Greenhouse Effect is real. There is no question that the presence of CO2 and other

greenhouse gases keeps this planet comfortably warm. The alarming crisis of Global

Warming arises from the ever-increasing concentrations of greenhouse gases in our

atmosphere as a direct result of human activity. All of the science suggests that

increasing greenhouse gas concentrations will inevitably lead to a rise in global

temperature. How much and how quickly temperature will rise is disputed.

Nonetheless, as scientists and citizens, we have a responsibility to act now, to educate

and work towards changing our habits to save the planet.

3.2 References

1. Web sites:

en.wikipedia.org

content.usatoday.com

library.thinkquest.org

www.usgcrp.gov

www.latexglove.info

www.ehow.com

www.esrl.noaa.gov

Documents

Assignment on NS 3 Greenhouse Part 2