Transcript Greenhouse Effects

Greenhouse
Management
Chapter 01
Introduction to Greenhouse
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Chapter Objectives
1.
2.
3.
4.
5.
Introduction
Types of greenhouse
Uses of greenhouse
Greenhouse effects
Global warming
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Introduction
• Introduction
– A greenhouse (also called a glasshouse) is a building
in which plants are grown. These structures range in
size from small sheds to industrial-sized buildings. A
miniature greenhouse is known as a cold frame.
– A greenhouse is a structural building with different
types of covering materials, such as a glass or plastic
roof and frequently glass or plastic walls; it heats up
because incoming visible solar radiation (for which the
glass is transparent) from the sun is absorbed by
plants, soil and other things inside the building.
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Introduction (Cont’d)
• Introduction
– Air warmed by the heat from hot interior surfaces
is retained in the building by the roof and wall.
– In addition, the warmed structures and plants
inside the greenhouse re-radiate some of their
thermal energy in the infrared spectrum, to which
glass is partly opaque, so some of this energy is
also trapped inside the glasshouse.
– However, this latter process is a minor player
compared with the former (convective) process.
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Types of Greenhouse
• Types
– Greenhouses can be divided into glass greenhouses
and plastic greenhouses.
– Plastics mostly used are polyethylene film and
multiwall sheets of polycarbonate material.
– Commercial glass greenhouses are often high-tech
production facilities for vegetables or flowers.
– The glass greenhouses are filled with equipment such
as screening installations, heating, cooling and
lighting, and may be automatically controlled by a
computer.
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Types of Greenhouse (Cont’d)
Types of Greenhouse
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Uses of Greenhouse
• Use
– Greenhouses allow for greater control over the
growing environment of plants.
– Depending upon the technical specification of a
greenhouse, key factors which may be controlled
include temperature, levels of light and shade,
irrigation, fertilizer application, and atmospheric
humidity.
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Uses of Greenhouse (Cont’d)
• Use
– Greenhouses may be used to overcome shortcomings
in the growing qualities of a piece of land, such as a
short growing season or poor light levels, and they
can thereby improve food production in marginal
environments.
– As they may enable certain crops to be grown
throughout the year, greenhouses are increasingly
important in the food supply of high-latitude
countries. One of the largest complexes in the world is
in Almeria, Spain, where greenhouses cover almost
50,000 acres (200 km2).
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Uses of Greenhouse (Cont’d)
• Use
– Greenhouses are often used for growing flowers,
vegetables and fruits. Special greenhouse varieties
of certain crops, such as tomatoes, are generally
used for commercial production.
– The relatively closed environment of a greenhouse
has its own unique management requirements,
compared with outdoor production
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Uses of Greenhouse (Cont’d)
• Use
– Pests and diseases, and extremes of heat and
humidity, have to be controlled, and irrigation is
necessary to provide water.
– Most greenhouses use sprinklers or drip lines.
– Significant inputs of heat and light may be
required, particularly with winter production of
warm-weather vegetables.
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Greenhouse Effects
• Greenhouse Effects
– A greenhouse is a house with transparent plastic
or glass roof and walls that is built to grow
vegetables, flowers or other plants in temperate
and colder countries.
– A greenhouse protects and provides heat to
plants: its roof and walls allow sunlight to enter
and prevent heat from escaping.
– This effect is known as the "greenhouse effect".
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Greenhouse Effects (Cont’d)
• Greenhouse Effects
– The earth's atmosphere contains some gases
known as greenhouse gases, which occur
naturally: water vapor, carbon dioxide, methane
(CH4), nitrous oxide (N2O), and ozone (O3).
– The layers of these gases naturally present in the
atmosphere acts as the roof of a greenhouse and
trap heat close to the earth's surface.
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Greenhouse Effects (Cont’d)
• Greenhouse Effects
– As a result, it maintains the mean temperature of
the earth’s surface at around 16°C, which is crucial
to ensuring climatic conditions that can support
life of animals and plants on earth.
– Since the industrial revolution, human activities
have caused substantial increases in
concentrations of greenhouse gases in the
atmosphere.
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Greenhouse Effects (Cont’d)
• Greenhouse Effects
– The main GHGs and their emission sources are:
• Carbon dioxide from burning fossil fuels (coal, oil,
natural gas), and from deforestation;
• Methane from rice paddies, livestock, waste dumps,
domestic sewage, coal mining;
• Nitrous dioxide mainly from chemical fertilizers used in
intensive farming, and from fossil fuel combustion;
• Chlorofluorocarbons (CFCs) from aerosol sprays, air
conditioner and fridge coolants.
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Greenhouse Effects (Cont’d)
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Greenhouse Effects (Cont’d)
• Greenhouse Effects
– The increased concentrations of greenhouse gases
in the atmosphere make the blanket or the "roof"
around the earth thicker, which in turn prevents
more and more heat from escaping into space.
– This disturbs the balance of heat exchange and
causes the air temperature to rise and that of the
earth's surface to rise.
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Greenhouse Effects (Cont’d)
• Greenhouse Effects
– In 1990, the Inter-governmental Panel on Climate
Change (IPCC), which consists of about 2,500
international scientists, confirmed that human
activities have contributed to climate change.
– It also concluded that if current greenhouse gas
emission trends continue, the mean global
temperature will increase by 3°C before the end of
the 21st century.
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Greenhouse Effects (Cont’d)
• Greenhouse Effects
– Climate change is having serious impacts on
agricultural production, water resources, human
health, coastal areas, forest and ecosystems.
– Increasing floods, droughts, windstorms and other
climate change related disasters, both in
frequency and intensity, have caused enormous
damages to many countries throughout the world.
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Greenhouse Effects (Cont’d)
b
a
c
d
The Greenhouse Effect
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Greenhouse Effects (Cont’d)
• Greenhouse Effects
– a) Solar radiation passes through the atmosphere and
warms the earth‘ surface;
– b) The earth's surface reflects heat back to the
atmosphere;
– Some of the heat escapes into space;
– c) The GHGs absorb some of the heat and re-emit back
to the earth's surface;
– d) As more GHGs are accumulated in the atmosphere,
more heat is trapped in the atmosphere causing
global warming.
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Global Worming
• Global Worming and Climate Change
– The atmosphere surrounding our planet acts as a
protective blanket for all life on earth.
– It provides carbon dioxide (CO2) for plant
photosynthesis and oxygen (O2) for animal and
human respiration.
– Historically, the climate has always dictated the
way people live:
• Housing;
• Clothing;
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Global Worming (Cont’d)
• Global Worming and Climate Change
– Historically, the climate has always dictated the
way people live:
• Diet;
• Agricultural practices;
• And some even believe that people's temperament
is determined by the climate;
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Global Worming (Cont’d)
• Global Worming and Climate Change
– In turn, the climate is regulated by many factors:
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Radiation and angle of the sun;
The rotation of the earth;
The geographical coordinates;
The chemical composition of air masses;
The proximity and size of the oceans;
The regional topography etc.
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Global Worming (Cont’d)
• Global Worming and Climate Change
– In particular, these factors control air temperature
and the amount and distribution of rainfall, which
are the two most important aspects of the climate
for a particular region.
– Changes in these factors will certainly lead to a
change in global climate.
– This will subsequently cause an impact on the way
we live.
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Global Worming (Cont’d)
• Global Worming and Climate Change
– For most of human history, changes in the earth's
climate have resulted from natural causes over
hundreds or even thousands of years.
– But since the industrial revolution over 200 years
ago, human activities have come to affect the
climate in serious and immediate ways – the
increasing emissions of greenhouse gases (GHG)
into the atmosphere are intensifying a natural
phenomenon called greenhouse effect.
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Global Worming (Cont’d)
• Global Worming and Climate Change
– This results in long-term rising of the average
temperature of the earth, which is called global
warming.
– With more heat trapped on Earth, the planet will
become warmer, which means the weather all
over Earth will change.
– For example, summers will get hotter, and winters
too.
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