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Science and Technology
The Nature and Development of Science and Technology
Case study – The important issues of science and technology
Case 5: Global Warming
Activity and case-based learning & teaching resources
Students’ version
Table of Content (Students’ version)
Outline
Aims of study
Scheme of work
Background information
Teaching Resources
Lesson 1, 2
Background
Activity 1: Case analysis
Activity 2: Drafted proposal on measuring the average temperature
at school
Additional background information
Extended activities
2
2
3
4
4
4–7
8
9
10
Lesson 3, 4
Background
Activity 3: Science experiments
Additional background information
Extended activities
11
11
11- 15
16- 19
20
Lesson 5, 6
Background
Activity 4: Case discussion
Activity 5: Reporting
Additional background information
21
21
21- 23
24
25- 26
1
Students’ version
Outline
Aims of study
The aim of these lessons is to introduce an important scientific issue – global warming – to
students. Students are led to realise the existence of global warming and understand its causes
and effects, so as to make self-reflections on the individual and social responsibilities. The lessons
would emphasize case study and analysis to enhance students’ abilities of thinking and critical
judgement of the problems. Through different group activities, students are encouraged to
exchange their ideas, help them to understand the constraints of scientific investigations and build
up the correct attitudes when exploring scientific evidences.
Scheme of work
Lessons
Learning objective
1, 2
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3, 4
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5, 6
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Teaching strategy
What is global warming?
Is global warming really
occurring?
How to measure the
average temperatures of
the earth?
Build up the attitude of
critical thinking toward
different scientific
explanations.
What are the causes of
global warming?
The relationship between
greenhouse effect and
global warming.
Science experiments

What are the influences
of global warming to us?
Movie watching
How do individuals and
societies face and solve
the problem of global
warming?
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Learning and teaching
resources
Case analysis

Links of articles
Group discussion (the 
PowerPoint
validity of global

Worksheet of case
warming)
analysis
Drafting a proposal 
Draft proposal
on measuring the
average temperature
at school
Experimental
simulation of
greenhouse effect on
the earth
Experiment
discussion (the causes
of greenhouse effect)
Movie watching
Case discussion (the
Kyoto Protocol)
Group discussion and
oral reporting (how to
face and solve the
problem of global
warming)
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Worksheet of the
experiment
PowerPoint
Links of articles
Worksheet on case
discussion
Assessment guidelines
of oral reporting
Links of articles
2
Students’ version
Background information
In the recent years, do you have a feeling that it is not as cold as before in winter and it is
much hotter in summer than the past? What is happening actually? Let us investigate on the
phenomenon of global warming.
Firstly we have to raise a question – Is the temperature on the Earth rising continually?
Some scientists use satellites to observe, to understand and to analyse the climatic changes on the
Earth, and they recognise that the Earth is becoming warmer. Some scientists have an opposing
idea to it since evidences show that the temperature of the Earth has been risen and dropped in
the last 100 years, they claim that temperature increases within a short period is simply a natural
phenomenon. Which statement is correct? Are there any data supporting it? Is temperature
increase a natural phenomenon or human made? What is its relationship with the phenomenon as
the ‘greenhouse effect’?
Solar radiation can supply light and heat on the Earth, 30% of its radiation energy is reflected
by clouds and the atmosphere and 70% is absorbed by the Earth surface. Part of the heat energy
reached the Earth surface then leaves the Earth in the form of infrared radiation. The atmosphere
absorbs the remaining part of the energy, which causes the air in the Earth become hot. The hot air
would then radiate in all directions with part of the energy reflected back to the Earth surface. The
continually circulating heat energy makes the earth become warmer and the phenomenon is called
‘the greenhouse effect’. The gases, such as carbon dioxide that absorb the radiation, are called
‘greenhouse gases’. The atmosphere is acting like the glasses of the greenhouses to trap the heat of
the gases for maintaining a suitable temperature, which allows people to live comfortably.
However, we need to concern when the amount of greenhouse gases exceeded the natural
level, they will become a calamity causing global warming. Actually, carbon dioxide is released
through respiration process of human and animals. But the intensive consumption of fossil fuels
(such as crude oil, coal or natural gases) adversely affects the global level of greenhouse gases
the most.
According to the report of the Intergovernmental Panel on Climate Change- IPCC, the
problem of global warming is more serious than we expected, as crisis will come if it is not dealt
with as soon as possible. The consequences brought about by the climatic change would
profoundly influence us. Melting of icebergs would submerge the cities, and natural disasters
would halt the agricultural productions, etc. With the rapid expansion of population and fast
technological development made recently, people have exploited the natural resources
excessively for pursuing a better living environment. It accelerates the expansion of the scope of
negative effects and causes unpredictable damages to the natural environment.
The seriousness of the problem is clear. In order to minimize the damages to the nature
caused by people, what can we do as an individual or a society? The lessons would be focused
on a case study and analysis to enhance students’ abilities of thinking and critical judgement of
the problem. Through reading, explanation, analysis and evaluation on the information about
global scientific discoveries and technological inventions, students can evaluate the reliability of
the situation claimed and understand the spirit of scientific investigation. Moreover, students
should actively take part in different group activities to exchange their ideas with other students
and teacher for complementation and exploring the domains of new knowledge.
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Students’ version
Teaching Resources
Lesson 1, 2: Is global warming occurring?
Background
Do you realise that the weather has been changed greatly in the recent years? In Hong
Kong, the winter has become much warmer in some days, the summer has arrived earlier and
become hotter and the number of warm days has increased too. What are the reasons behind? Do
the same situation occur all over the world? According to the record from the Global Temperature
Logger, the last 10 years in the 20th century are included in the warmest 15 years from the middle
of the 19th century, with 6 years having the highest recorded temperature. The situation is unusual
in the past. What will the climate be in the coming 100 years or 1000 years then?
Actually, the climate and seasons of the Earth are affected by the solar radiation. The regional
climatic characteristics are depended on the amount of solar radiation received. Moreover, some
natural phenomenon such as El Niño and volcano eruption would lead to short term climatic
fluctuation and cause abnormal climates such as having the warmer or colder winter. As a result,
we cannot claim that global warming is happening according to the fact of higher temperatures in
the recent years only. In the long term, we still need to do more researches, observations and data
collection to prove whether the climatic trend is warming.
The name of global warming is obtained from observations. The atmosphere closer to the
Earth surface become warmer that occurs without any signs. Its seriousness is unpredictable too.
The phenomenon of warming is one of the various climatic changes which scientists have proved
its happening in earlier time. How do the scientists make these conclusions? What kinds of
experiments have to be carried out? How to analyse the data?
The rise of temperature would bring about impacts and influences on people’s activities. For
examples: Where can we live? What kinds of crops can we grow? Where should we grow?
Where are the places that the organisms (such as pests) reproduce rapidly? Do we have to confirm
the occurrence of global warming before preventing these hidden impacts? If it does occur, what
are the extent and reasons of global warming?
Activity 1: Case study
The issue of global warming is concerned by different organisations and mass media worldwide
and it is not difficult for us to see the related reports in our daily lives. We can have a look on the
news and information worldwide first, and analyse the problems related to warming from the
reports and cases. Students should judge whether the global warming is a real situation or not.
Please read the case below:
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Students’ version
Case 1.
Greenpeace marks CLP's 'unhappy' birthday for the
climate (Extract)
http://www.greenpeace.org/china/en/press/releases/greenpeace-marks-clp-s-unhapp
January 25, 2005
Hong Kong, China — Greenpeace descended on the Kowloon headquarters of China Light &
Power (CLP) today, to mark its 104th anniversary and over a century of environmental
pollution. The green group declared the occasion an "unhappy birthday" for Earth's climate
after naming and shaming CLP's coal burning operations all across Asia as a major contributor
to climate change.
Three volunteers then removed their T-shirts to reveal the slogan: "Stop Global Warming"
painted on their bodies. Gloria Chang, Greenpeace Climate & Energy campaigner presented a
birthday card to CLP, calling on the company to halt its planned expansion in coal power and to
invest in clean renewable energy instead.
Gloria Chang said: "Today is a sad day for the climate as it marks 104 years of CLP's climate
crimes. Burning coal destroys our climate. CLP must take responsibility for over a century of
causing climate change and stop investing in coal power now."
Gloria Chang continued: "Climate change is happening now: the world is getting hotter and
hotter, and we are already paying the social and economic cost. The World Health Organization
says Climate change is already killing over 150,000 people each year and it's going to get much
worse unless companies like CLP clean up their act. CLP must halt its investments in new coal
projects and urgently invest in clean, renewable energy instead."
Case 2.
Global warming could be twice as bad as feared
(Extract)
http://www.spacedaily.com/2005/050126182825.zf2d1n9e.html
26 January, 2005
Global warming may be twice as bad as expected, according to a new assessment of a
commonly-used yardstick of possible carbon dioxide (CO2) pollution.
Until now, most computer models of climate change predict that if atmospheric levels of CO2
reach double of the pre-industrial age, the Earth's surface temperature will be between two and
five C (3.6-9.0 F) warmer when compared with 1990 levels.
But a study published Thursday in the British science journal Nature suggests that the
temperature rise could be much higher -- of between nearly two (3.6 F) and more than 11 C
(19.8 F).
The research comes from a highly ambitious project in "shared computing," in which more than
90,000 people in more than 140 countries downloaded a special programme to crunch through
data on their personal computer.
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Students’ version
The gas hangs in the atmosphere, trapping heat from the Sun that otherwise would radiate safely
back into space.
Scientists say this unbridled pollution is bound to have an effect on the world's
delicately-balanced climate system.
Their big challenge, though, is to figure out when, where and how the effects will kick in, and if
the change will be gradual or if there will be a "tipping point" beyond which change will be
cataclysmic.
While there are many uncertainties, recent evidence suggests that carbon pollution is worsening
faster than thought and that the first signs of climate change are already visible, in the form of
extreme weather events such as recurrent El Ninos, droughts, floods and storms.
Try to answer the questions below:
1. According to case 1, what are the purposes of the actions of the members of Greenpeace for
the campaign?
___________________________________________________________________________
___________________________________________________________________________
2. Can you suggest some kinds of renewable energy production method that can be used by
CLP?
___________________________________________________________________________
___________________________________________________________________________
3. According to case 2, what kinds of information about global warming were discovered?
___________________________________________________________________________
___________________________________________________________________________
4. What are the expected consequences on the Earth due to global warming?
___________________________________________________________________________
___________________________________________________________________________
5. According to what you have observed in the daily life, what kinds of information have
proved the occurrence of global warming?
___________________________________________________________________________
___________________________________________________________________________
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Students’ version
6. Do the information reliable?
___________________________________________________________________________
___________________________________________________________________________
7. What kinds of discovery do scientists make about the climatic changes recently? Have
you ever heard of your parents talking about the difference of climates in the past and the
present?
___________________________________________________________________________
___________________________________________________________________________
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Students’ version
Activity 2: Drafting a proposal on measuring the average
temperature at school
To do scientific researches, primarily scientists have to raise questions about the incidents and carry
out further investigations to obtain the final conclusion. While they are conducting experiments and
collecting information, the first thing they have to prepare is finding the ways to measure the
information. The accuracy and reliability of information is extremely important during researches.
The researchers have to notice any uncertainties that may affect the results including natural and
human factors. Finally, the conclusion is made after detailed information analysis.
For the problem of global warming, scientists have to find out the ways to measure the average
temperature of the Earth. What are the most reliable and accurate ways for measurement? Now,
teacher will divide students into groups of 4 to 5 people to simulate the work of scientists –
measuring average temperature. So a proposal for measuring the average temperature at school
would be drafted with detailed procedures.
The content of proposal:
1. Aims:
_________________________________________________________________________
_________________________________________________________________________
2. Procedures:
Hints:iii) Which kind of apparatus should be used for measurement?
iii) Where should the apparatus be placed?
iii) How many days should the measurement be taken for and how many times should it be
taken daily?
iv) How to analyse the information after collecting the data?
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
3. Analysis:
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
Questions to think: After finished the proposal, do you think it is difficult to measure the
average temperature? Is the information accurate? What are the factors
affecting the results of measurement? Would the obtained data be
questioned by others?
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Students’ version
Additional background information:
What are the evidences proving that global warming is occurring?
According to a report from the Intergovernmental Panel on Climate Change (IPCC), the global
average temperature has increased for about 0.8℃ from 13.5℃ to 14.4℃ during the last 140
years. However, the change is not absolutely one-sided. The surface temperature of the Earth has
been increased rapidly since 100 years ago. The first warming period is from 1910 to1945, which
is then followed by another cold period for 30 years. Since 1976, the temperature has been
increased continually until now and we are at a temperature-increasing trend at the moment (see
Figure 1). In the same way, the measured horizontal height of seawater is also fluctuating. The
monitoring stations at Amsterdam and Bucharest show that the average water level of seawater has
increased for 130 mm in the last 100 years too.
How do scientists measure the information needed?
Due to the technological development, many countries worldwide have their observatories to
measure and monitor changes in weather or using satellites to do so. To know the average
temperature of a country or of the Earth’s surface, scientists can easily obtain various information.
However, special monitoring stations are needed for measuring sea level and the composition of
substances in the air (such as the Mauna Loa Observatory in Hawaii).
For measuring the area and thickness of ice coverage at the North and South Poles, direct
measurement is needed in addition to rely on satellites. The US Navy has sent submarines to
measure the depth of sea ice in 1950s and 1990s. The depth was about 3.1 ft in 1950s and about
1.8 ft in 1990s. The significant drop of 42% showed the thickness of ice layer is reducing
continuously.
Changes in average temperature in ℃(1860 – 2000)
0.8
0.8
0.4
0.4
0.0
0.0
-0.4
-0.4
-0.8
-0.8
1860
1880
1900
1920
1940
1960
1980
2000
Figure 1
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Students’ version
Extended activity:
Measuring regional temperature
Although the area of Hong Kong is about 1000 km2 only, the pollution densities and geographical
environment are different and so the temperatures are not necessarily the same. The temperature
differences between urban districts and the New Territories are significant. In cloudless winter
night and day with weak wind, open areas have a greater range of temperature drop than urban
areas. The significant temperature drop is due to the fast heat-dissipating rate of the ground as air
cannot keep the heat energy. The phenomenon is similar to a hot drink not covered by a lid,
which would cool down more quickly. As a result, the temperatures in some regions in the New
Territories (such as Lau Fou Shan, Da Kwu Ling) would be lower than urban areas for 5 to 6℃
or even 10℃ .
Students can try to measure the indoor temperature of their home and draw a trend line for
analysis and compare with other students.
Extended questions (students should find out the answer by themselves)
1. How reliable are the temperature and the height of sea level simulated by computers?
2. What is the information used by scientists as the basis for computer simulation?
3. How can scientists know the weather conditions in 100 years ago?
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Students’ version
Lesson 3, 4: What are the causes of global warming?
Background
The function of solar radiation is supplying light and heat to the Earth and allows energy to
be trapped in the Earth surface by the ‘greenhouse effect’. The greenhouse gases in the atmosphere
(such as carbon dioxide and methane) act like glasses of the greenhouse to trap the heat energy
from the sun. Students should bear in mind that the greenhouse gases construct a warm and
comfortable living environment for us and provide a place of ease and comfort to human and
animals. Owing to the presence of the atmosphere, the average temperature of the Earth is
comfortable at around 15℃ now and not at the freezing -18℃. The difference in temperature is
due to the greenhouse gases, which absorbs infrared radiation to affect the overall energy balance
of the Earth. Using the moon as an example, without the protection of the atmospheres, the heat
energy cannot be trapped. It leads to big temperature differences between day and night and make
it unsuitable for humans to live in.
Another problem of our concern relates to the amount of greenhouse gases, if they exceed the
natural level, calamity will be caused. As more heat energy is trapped in the Earth, global warming
is resulted. The atmosphere is composed of different gases and only about 1% of them are
greenhouse gases generated from the natural world. In fact, carbon dioxide is released through the
respiration process of humans and animals, which is the law of living organisms.
Global warming is a major concern of lots of scientists even though they have different
opinions. Some scientists believed that people are accelerating this process. People’s activities for
improving their living quality would increase the global amount of greenhouse gases for the most.
After the Industrial Revolution, people use machines for mass production and develop new
technologies. The excessive consumption of fossil fuels used by cars and factories (such as crude
oil, coal and natural gases) produce gases causing global warming. Furthermore, the intensive
farming on agricultural lands and excessively cutting down trees in the forests also cause the
natural world losing balance. The increase of greenhouse gases continually leads to temperature
increase. However, some scientists have different viewpoints: the cause of global warming is from
the natural world itself. The controversy provides us rooms for thoughts.
It is important to have different ideas in science as it allows us to determine what to do next.
That leads to the progression of the society. Should we change our present lifestyle to stop
driving private cars and give up the luxurious lifestyles? Maybe we can make changes so that the
nature can return to the normal cycles. In the lessons, students may think about the concepts and
causes of global warming and investigate further the supporting evidences of the different
viewpoints stated above.
Activity 3: Science experiment
The function of solar radiation is supplying light and heat to the Earth and allows energy to be
trapped in the Earth surface by the ‘greenhouse effect’. The greenhouse gases in the
atmosphere (such as carbon dioxide and methane) act like glasses of the greenhouse to trap the
heat energy from the sun. Students should bear in mind that the greenhouse gases construct a
warm and comfortable living environment for us and provide a place of ease and comfort to
humans and animals. Using the moon as an example, without the protection of the
atmospheres, the heat energy cannot be trapped. It leads to big temperature differences
between day and night and makes it unsuitable for humans to live in. Another problem of our
concern relates to the calamity caused by the amount of greenhouse gases exceeded the natural
12
Students’ version
level. As more heat energy is trapped in the Earth, global warming is resulted. In fact, carbon
dioxide is released through the respiration process of humans and animals, which is the law of
living organisms. The most influential factors affecting the amount of greenhouse gases are
peoples’ activities to enhance their living quality included the use of machines and
development of new technologies. The excessive consumption of fossil fuels used by cars and
factories (such as crude oil, coal and natural gases) produce gases causing global warming.
Furthermore, the intensive farming on agricultural lands and excessively cutting down trees in
the forests, etc. are also the causes.
1. Objective
In the activity, students will become young scientists. Students have to act like scientists using
verification method by setting up experiments for simulating the greenhouse effect of the Earth.
You will understand the greenhouse effect, investigate the phenomenon of global warming and
evaluate the accuracy of the experiment.
2. Theory
The sun is the origin of a large amount of heat energy. This kind of heat energy can travel through
the space through radiation. When the radiation hits on an object, such as the Earth, the object
would warm up after absorbing energy. The warmed object will then emit energy to the space by
radiation. The greenhouse gases in the atmosphere, such as the water vapour and carbon dioxide
would absorb some of the radiation emitted from the Earth. When the atmosphere becomes
warm, the heat energy will be radiated back to the Earth. The Earth absorbs the energy and
becomes warmer. The alternation of radiation occurs continuously.
3. Materials（each group）
2 two-litre transparent soft drink plastic
bottles
2 thermometers
2 colour pens
1 piece of 20"x20" cling film
1 100-watt light bulb
1 piece of wooden block for fixing the
position of the lamp (if necessary)
3 pieces of thin cardboard 1"x 2"
4 cups of soil
1 medium-sized rubber band
Adhesive tape
Desk lamp without shelter
4 pieces of graph paper (with 1/4"
grids)
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Students’ version
Cut to open the transparent
plastic bottle
Wooden block
Bottle covered by cling
film with rubber band
Thermometer
Thin cardboard
Light bulb
Soil
Soil
Thermometer placed
inside the bottle
Thin cardboard
The set-up of experiment on greenhouse effect
4. Experiment procedure
a.
Use the wooden block to fix the light bulb. Test if all light bulbs function well.
b. Use adhesive tape to stick the thermometers and cardboards inside the bottles. The
anterior part on the thermometers should face outside (the markings can be seen) and
thermometers should be far away from the light source. This point is very important.
c.
Put 2 cups of soil into each bottle.
d. Cover one of the bottles with cling film and rubber band.
e.
Place the bottles at a distance of 2 inches beside the light bulb. Measure the space with
1" x 2" cardboards.
f.
Predict what will happen.
g.
Record the temperature of the bottles before switching on the light bulbs.
h. During the next 30 minutes, record the temperatures of the bottles every 2 minutes.
i.
Switch off the light bulb and record the temperatures of the bottles in the next 6
minutes.
j.
Collect the data and present the result in graph.
k. Add a title to the graph and use suitable measurement units.
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Students’ version
Information recording sheet
Observed results
Time（minutes）
Temperatures of the opened
bottle （oC）
Temperatures of the closed
bottle （oC）
Graph
Opened bottle
Temp
Cling film wrapped bottle
Time
15
Students’ version
Analysis and explanation
1.
Why does the temperature rise?
__________________________________________________________________________
2.
Why does the temperature reach equilibrium?
__________________________________________________________________________
3.
Which bottle has the highest temperature increase?
__________________________________________________________________________
4.
Why does the closed bottle need a higher temperature for reaching equilibrium than the
opened bottle?
__________________________________________________________________________
__________________________________________________________________________
Practical application（Extra questions）
1.
How can your model represents the greenhouse effect?
__________________________________________________________________________
__________________________________________________________________________
2.
Why is it important to record the temperature of the box after switching off the light?
__________________________________________________________________________
__________________________________________________________________________
3.
What are the expected consequences if air pollution continues to worsen?
__________________________________________________________________________
__________________________________________________________________________
4.
If this model is regarded as too simple, how to improve the model design?
__________________________________________________________________________
__________________________________________________________________________
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Students’ version
Additional background information:
What is the main cause of global warming?
There are many causes of global warming including natural and human factors. For natural
factors, some people suspect that the sun has released more energy. However, scientific
evidences have rejected the idea. Scientists have measured the amount of solar radiation received
by the Earth and discovered that the amount of radiation emitted by the sun has not been changed
greatly before they draw their conclusions. Scientists think that there are several natural factors
causing global warming:
(a) The distance between the Sun and the Earth has been changed that leads to increase or
decrease of the radiation reaching the Earth.
(b) The problem of the amount of black spot. Some scientists think that when the amount of
black spot increased, the amount of radiation increased as well. But this point cannot be
proved by satellite measurement.
(c) The plate tectonic movement and the change of the landscape induce volcano eruption and
cause temperature decrease in the short-term.
There are two human factors, the first is the changes in atmospheric composition and the second
is the change in shape and appearance of landscape.
The expanding population and the rapid development of technology are also keys affecting the
human factors. In about 1000 years ago, the world population was only about 600 millions and it
was about 1 billion even in 1900. Nowadays, the world population reaches 6 billions already
under a tremendous growth rate. It is estimated that another 5 billions will add on the population
in the coming 200 years, which means the population will be 11 billions at that time. The more
people, the more resources needed and the use of cars and industrial fossil fuels will be increased
too. These are the major factors leading to the increase of greenhouse gases.
Moreover, the overuse of lands, intensive farming of agricultural land and excessive cutting of
trees in primeval forests, all lead to lose of balance in the natural world. The natural cycle of
climate is interfered by human factors that leads to global warming as well.
What is Greenhouse Effect?
The “Greenhouse Effect” is a term that refers to a physical property of the Earth's atmosphere. If
the Earth had no atmosphere, its average surface temperature would be very low of about -18℃
rather than the comfortable 15℃ found today. The difference in temperature is due to a suite of
gases called greenhouse gases, which affect the overall energy balance of the Earth's system by
absorbing infrared radiation. In its existing state, the Earth-atmosphere system balances
absorption of solar radiation by emission of infrared radiation to space (Fig. 1). Due to
greenhouse gases, the atmosphere absorbs more infrared energy than it radiates back to space,
resulting in a net warming of the Earth-atmosphere system and of surface temperature. This is
the “Natural Greenhouse Effect”. With more greenhouse gases released to the atmosphere due to
human activity, more infrared radiation will be reflected back to the Earth's surface, which
contributes to the “Enhanced Greenhouse Effect”.
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Students’ version
Fig. 1 A simplified diagram illustrating the global long-term radiative balance of the atmosphere.
Net input of solar radiation (240 Wm-2) must be balanced by net output of infrared radiation.
About a third (103 Wm-2) of incoming solar radiation is reflected and the remainder is mostly
absorbed by the surface. Outgoing infrared radiation is absorbed by greenhouse gases and by
clouds keeping the surface about 33℃ warmer than it would otherwise be.
Types of Greenhouse gases
Greenhouse gases comprise less than 1% of the atmosphere. Their levels are determined by a
balance between “sources” and “sinks”. Sources and sinks are processes that generate and
destroy greenhouse gases respectively. Human affects greenhouse gas levels by introducing new
sources or by interfering with natural sinks activity.
The major greenhouse gases in the atmosphere are carbon dioxide (CO2), methane, (CH4),
nitrous oxide (N2O), chlorofluorocarbons (CFCs) and ozone (O3). Atmospheric water vapour
(H2O) also affects significantly the natural greenhouse effect but it is thought that its presence is
not directly influenced by human activity. Characteristics of some of the greenhouse gases are
shown in Table 1.
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Students’ version
Trends in greenhouse gas concentrations
a) Carbon Dioxide (CO2)
High-quality observations of the concentration of CO2 began in 1958, with flask
measurements at the Mauna Loa Observatory in Hawaii. Fig. 2 shows that the
average annual concentration of CO2 in the atmosphere has risen from about 315
ppmv (part per million by volume) in 1958 to around 363 ppmv in 1997. There is
a clear annual cycle in the Mauna Loa data that corresponds to the annual cycle of
plant respiration in the Northern Hemisphere: CO2 concentration increases during
the Fall and Winter and reduces during the Spring and Summer. This cycle,
follows the growth and withering of vegetation, but is reversed and of smaller
amplitude in the Southern Hemisphere, and this phenomenon cannot be observed
from the data measured near the Equator.
Fig. 2 Atmospheric carbon dioxide monthly mean mixing ratios. Data prior to May 1974 are
from the Scripps Institution of Oceanography (‧ ), data since May 1974 are from the U.S.
National Oceanic and Atmospheric Administration (‧ ). A long term trend curve (— ) is fitted to
the monthly mean values.
b) Methane (CH4)
The rate of increase of the atmospheric abundance of methane has declined over
the last decade, dramatically lowered between 1991 to 1992, though with an
apparent increase in the growth rate in late 1993 (Fig. 3). The average trend over
1980 to 1990 is about 13 ppbv (part per billion by volume) annually.
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Students’ version
Fig. 3
Atmospheric methane mixing ratios from discrete air samples collected at Mauna Loa, Hawaii. A smooth
curve (red) and long term trend (green) are fitted to the measurements (blue).
Table 1: Characteristics of some major greenhouse gases
Greenhouse gas
Sources
Sinks
Importance for climate
Carbon Dioxide
(CO2)
1) Burning of fossil fuel
2) Land-use change
(deforestation)
1) Ocean Uptake
2) Plants’ photosynthesis
Absorbs infrared radiation;
affects stratospheric O3
Methane
(CH4)
1) Biomass burning
2) Enteric fermentation
3)Rice paddies
1) Reactions with OH
2) Microorganisms uptake
by soils
Absorbs infrared radiation;
affects tropospheric O3 and
OH; affects stratospheric
O3 and H2O; produces CO2
Nitrous Oxide
(N2O)
1) Biomass burning
2) Fossil-fuel combustion
3) Fertilizers
1) Removal by soils
2) Stratospheric photolysis
and reaction with O
Absorbs infrared radiation;
affects stratospheric O3
Ozone
(O3)
Photochemical reactions
involving O2
Catalytic chemical reactions
involving NOx, ClOx and
HOx species.
Absorbs ultraviolet and
infrared radiation
Carbon Monoxide
(CO)
1) Plant emissions
2) Man-made release
(transport, industrial)
1) Soil uptake
2) Reactions with OH
Affects stratospheric O3
and OH cycles; produces
CO2
Chlorofluorocarbons
(CFCs)
Industrial production
Insignificant in troposphere,
dissociated in stratosphere
(photolysis and reaction with
O)
Absorbs infrared radiation;
affects stratospheric O3
1) Volcanoes
2) Coal and Biomass burning
1) Dry and wet deposition
2) Reactions with OH
Forms aerosols, which
scatter solar radiation
Sulphur Dioxide
(SO2)
Source:
Hong Kong Observatory
http://www.weather.gov.hk/wxinfo/climat/greenhs/e_grnhse.htm
<The article is edited by Education Bureau, Curriculum Development Institute (Science
Education Section)>
20
Students’ version
Extended activities:
According to the theory of scientists, the larger amount of greenhouse gases, the higher heat
absorption capacity it has. Is the theory accurate? Does the amount of greenhouse gases have
direct effect on the temperature? Students can modify the science experiment done before to
verify it by them. The suggested modifications are listed below:
1. Place plants in the simulated greenhouse
Plants have the function to balance the ecosystem on the Earth. They will absorb carbon dioxide
and release oxygen to balance the gas content. We can place a small pot of plant into the
uncovered simulated greenhouse, and than cover it by cling film without changing other settings
to repeat the experiment done before.
Since the plant would absorb carbon dioxide, we can predict that the effect of greenhouse would
be slightly weaker than normal and the temperature would be lower as a result.
2. Change the air by the gas we breathe out
When air is breathed in our body, gas exchange occurs to release excess carbon dioxide from the
body. As a result, the carbon dioxide content in the air we breathe out would be higher than
normal air. We can use the uncovered simulated greenhouse, cover it by cling film without
changing other settings after adding the air we breathe out for the experiment.
Since the carbon dioxide content of the air we breathe out is higher than normal air, we can
predict that the effect of greenhouse would be slightly stronger than normal. As a result , the
temperature would be higher.
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Students’ version
Lesson 5, 6: What are the influences of global
warming to us?
Background
Accompanying with the rapid population growth and the advances of technology, people are
continually striving for more living spaces to seek for better living environment. The excessively
use of resources has brought the impact on climatic change. Another calamity of the climatic
change in time may create profound influences inducing such as the reduction of area of forest,
the pollution of the Earth, water sources and air, and ozone layer depletion, etc. Other natural
disasters such as flooding, drought and typhoon may also be caused.
Global warming is an extremely serious problem, which influences people and the natural
environment greatly. Although scientists continually predict the temperature changes in the future
and simulated by computers, they still cannot accurately predict the results owing to the
uncertainties exist. What we can confirm is that it would become crises for people in the future if
the condition were kept worsening.
Now it is the time for people to make decision about our future and we must change our
livings. From the social and individual aspects, what kind of actions can we take for it?
We should try to reduce the emission of greenhouse gases by all means as most of the
greenhouse gases are produced in our daily life. For example, even vehicles, air conditioners and
electricity are all necessities, we can try using them wisely: travelling more by public transport
vehicles, a few persons with one car rather than driving individually, remember to switch off all
the electrical appliances to save energy, etc. Can you suggest more ideas to make the Earth
become a better place to live?
We should recognise that: it is a mutual responsibility for all nations to construct a pleasant
society and protect the global environment. All nations can legislate to regulate the greenhouse
gases emission level of factories and electric power stations, invest on the resources for
developing environmental saving energies and sign international treaties to constrict the
greenhouse gases emission level of each nation. These are what people can do and also what
people should do too.
Activity 4: Case discussion
Accompanying with the rapid population growth and the advances of technology, people are
continually striving for more living spaces to seek for better living environment.
The crisis of global warming is on the verge of breaking out. If it is not solved earlier, the crisis
caused by the climatic changes will influence us greatly: individual health, drinking water
sources, natural ecological environment, melting of icebergs, flooding of coastal lowlands, etc.
So we could not ignore it. To reduce the negative influence of people to the natural environment,
what can we do individually and socially?
22
Students’ version
Study the case below:
The Kyoto Protocol
The Second Conference Of The Parties (COP-2) to the U.N. Framework Convention On
Climate Change (FCCC) wrapped up in Geneva on July 19, 1996 as one hundred and thirty
four governments adopted a Ministerial Declaration that committed themselves to the
negotiation of "legally binding" greenhouse gas targets aimed at "substantial overall"
reductions for industrialized countries by the end of 1997. They also said that the continued
increase in greenhouse gas concentrations would lead to "dangerous" climate change.
The Ministerial Declaration resulted from a positive step forward by the United States,
which after years of obstruction, called for legally binding targets. The Ministerial
Declaration's significance is that it calls for "legally binding" emission obligations for
"significant overall" emission reductions. This provides very strong direction to the final stage
of the Berlin Mandate and lead up to the Third Conference of the Parties (COP-3) in Kyoto,
Japan in 1997.
http://archive.greenpeace.org/climate/cop2/
Delegates to the various subsidiary bodies of the UN Framework Convention on Climate
Change met in Bonn, Germany, in February and March 1997 to formulate proposals for a
protocol or other legal instrument intended to be adopted at the Third Session of the
Conference of the Parties to be held in Kyoto, Japan, 110 December. The discussions centered
mainly on timetables and targets for emission reductions, the issue of coordinated versus
flexible policies, whether different developed countries should have different targets or not,
and the implications for developing countries.
The ad hoc Group on the Berlin Mandate (AGBM) met in Berlin from 3 to 7 March 1997 to
discuss future reductions in greenhouse-gas emissions by developed countries. During the
talks, the European Union challenged other countries to a 15 per cent cut in emissions by the
year 2010, compared with 1990 levels.
http://www.wmo.ch/web/catalogue/New%20HTML/frame/engfil/wcn/preview.html
The Third Conference of the Parties (COP-3) to the United Nations Framework Convention
on Climate Change (FCCC) was held from 1 - 11 December 1997 in Kyoto, Japan. Over
10,000 participants, including representatives from governments, intergovernmental
organizations, NGOs and the press, attended the Conference, which included a high-level
segment featuring statements from over 125 ministers. Following a week and a half of intense
formal and informal negotiations, including a session on the final evening that lasted into the
following day, Parties to the FCCC adopted the Kyoto Protocol on 11 December.
In the Kyoto Protocol, Parties in Annex I of the FCCC agreed to commitments with a view
to reducing their overall emissions of six greenhouse gases (GHGs) by at least 5% below 1990
levels between 2008 and 2012 (Annex B lists quantified emission limitation or reduction
commitments for Annex I Parties, which range from an 8% decrease to a 10% increase of
GHG emissions from 1990 levels to be reached in a period between 2008 and 2012. The EU
countries are to reduce GHG emissions from 1990 levels by 8%, the US by 7%, Japan by 6%,
while countries like Australia and Iceland are allowed increases by 8% and 10%, respectively.
The Russian Federation is to maintain its emissions at 1990 levels). The protocol also
establishes emissions trading, joint implementation between developed countries, and a "clean
development mechanism" to encourage joint emissions reduction projects between developed
and developing countries.
http://www.iisd.ca/vol12/enb1276e.html
23
Students’ version
In 2001, the president of the United States stated to give up the support to the Kyoto
Protocol with the reason that they were suspicious on the accuracy of the scientific information.
However, the United States claimed that they would seek out other methods from researches to
prevent the happening of global warming. The United State has agreed to follow the protocol
that reduces the exhaust emission by 7%. However, they disagreed with the fact that
developing countries included China and India were not included in the area of regulations.
The United State believed that it would ruin their economies.
N.B. COP-2 is the Second Conference of Parties to the U.N. Framework Convention On Climate
Change (FCCC), COP-3 is the Third Conference of Parties to the U.N. F.C.C.C.
Students need to answer the questions below:
1. Why did the Kyoto Protocol need to be established?
2. What is the content of the Kyoto Protocol? Is this method effective?
3. Why did the United States refuse the protocol finally?
(Would China accept the Kyoto Protocol? Why?)
4. What is the role of Hong Kong in the issue?
5. What should the responsibilities of the society be undertaken for solving the problem of
global warming?
6. What can individuals do to solve the problem of global warming?
24
Students’ version
Activity 5: Oral Reporting
After reading the article about the Kyoto Protocol, students should recognise that the
international society has already taken actions to prevent global warming from occurring
continually. In addition to establishing some international laws, are there any other solutions to
solve the problem? What can we do individually? What can be done socially? Students are
now divided into groups of 4 to 5 to think about the solutions together. A 5 minutes oral
reporting has to be performed by each group.
Some points to note:
1. More understanding on the topic
2. Collect information and detailed analyse in detail
3. Sharing of duties
4. Supporting resources
Teacher can consider the items below as assessment criteria:
Item
Topic
Content
Related topics and the key points
illustrated
Evidence and information Appropriately quote and provide
evidence and information
Analysis
Clear and logical analysis
Structure
Well-organized structure
Presentation
Clear and effective presentation
Collaboration
Collaborating among groupmates
Contents of discussion and reporting:
- The extent, seriousness, speed and location of global warming
- What are the other solutions to tackle the problem other than establishing laws
- What can be done individually?
- What can be done socially?
25
Students’ version
Additional background information:
Consequences of Enhanced Greenhouse Effect
1) Global Warming
Increase of greenhouse gases concentration causes a reduction in outgoing
infrared radiation, thus the Earth's climate must change somehow to restore the
balance between the absorption and release of radiation. This “climatic change”
will include a “global warming” of the Earth's surface and the lower atmosphere
as warming up is the simplest way for the climate to release of the extra energy to
space through radiation. However, a small rise in temperature will induce many
other changes, for example, cloud cover and wind patterns. Some of these changes
may act to enhance the warming (positive feedbacks), others to counteract it
(negative feedbacks).
Using complex climate models, the "Intergovernmental Panel on Climate Change"
in their third assessment report has forecasted that the global mean surface
temperature will rise by 1.4℃ to 5.8℃ by the end of 2100. This projection takes
into account the cooling effects of air particulates in the atmosphere on the Earth’s
climate as well as the delaying effects of the oceans, which have a large thermal
capacity. However, there are many uncertainties associated with this projection
such as future emission rates of greenhouse gases, feedbacks on climate, and the
magnitude of the ocean delay effect...etc.
2) Sea Level Rise
If global warming really takes place, sea level will rise due to two different
processes. Firstly, warmer temperature causes sea level to rise due to the thermal
expansion of seawater. Secondly, water from melting glaciers and the ice sheets of
Greenland and the Antarctica would also add water to the ocean. It is predicted
that the Earth's average sea level will rise by 0.09 to 0.88 m between 1990 and
2100.
Potential Impact on human life
1) Economic Impact
Over half of the human population lives within 100 kilometers of the coast. Most
of this population lives in urban areas near the harbours. A measurable rise in sea
level will have a severe economic impact on low-lying coastal areas and islands,
for examples, increasing the beach erosion rates along coastlines, rising sea level
displacing fresh groundwater for a substantial distance inland.
2) Agricultural Impact
Experiments have shown that with higher concentrations of CO2, plants can grow
bigger and faster. However, the effect of global warming may affect the general
atmospheric circulation and thus altering the global precipitation pattern as well as
changing the soil moisture contents in all continents. Since it is unclear how
global warming will affect the local or regional climate, the probable effects on
the vegetation remains uncertain.
3) Effects on Aquatic systems
The loss of coastal wetlands could certainly reduce fish populations, especially
shellfish. Increased salinity in estuaries could reduce the species and amount in the
26
Students’ version
freshwater but could increase the number of marine species. However, the full
impact on marine ecology is not known.
4) Effects on Hydrological Cycle
Global precipitation is likely to increase. However, it is not known how regional
rainfall patterns will change. Some regions may have more rainfalls, while others
may have less. Furthermore, higher temperatures would probably increase
evaporation. These changes would probably create new pressure on the use of
water resources.
5) Effects on Forests
The sudden changes in weather would decrease the species richness of trees due to
failure of adapting abnormal climate and shortage of water sources. The forest
areas would diminish and the health and quality of trees would deteriorate.
6) Effects on Human
Sudden climatic changes cause people to adapt to new weather continually and
lead to more sicknesses. Moreover, air pollution makes people more likely to
suffer from respiratory diseases with increasing incidence.
Source: Hong Kong Observatory
http://www.weather.gov.hk/wxinfo/climat/greenhs/e_grnhse.htm
<The article is edited by Education Bureau, Curriculum Development Institute (Science
Education Section)>
27