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Information Folder (1)—Global Warming 1
Contents
Page
Contents--------------------------------------------------------------------1
‘Natural’ Greenhouse Effect---------------------------------------------2
‘Enhanced’ Greenhouse Effect------------------------------------------3
Global climate change—a natural or human-induced
phenomenon?--------------------------------------------------------------4
Effects of global warming------------------------------------------------5
References------------------------------------------------------------------7
Information Folder (1)—Global Warming 2
The earth receives incoming
solar radiation from the sun during
the day and warms up. At night, it
loses heat through emission of
radiation to space. However, the
greenhouse gases (such as carbon
dioxide, methane and nitrous oxide)
in the atmosphere absorb some of
the outgoing radiation and
re-radiate it back to the earth’s
surface again. Heat is thus retained
in the atmosphere like a
greenhouse. This is ‘natural’
greenhouse effect.
‘Natural’ greenhouse effect is
important. If there is no ‘natural’
greenhouse effect, the average
surface temperature of the earth
will be -18°C instead of 15°C today.
Information Folder (1)—Global Warming 3
Since the beginning of the Industrial Revolution, the natural
balance of the earth’s energy budget has been influenced by human
activities. Large amount of greenhouse gases, mainly carbon dioxide,
are released from factories, power stations and motor vehicles. With
increasing use of fossil fuels, more greenhouse gases concentrated in the
atmosphere. Besides, deforestation and the burning of tropical rain
forest also release huge amount of carbon dioxide into the atmosphere.
All these alter the chemical composition of the atmosphere and result in
the building up of greenhouse gases and contribute to the ‘enhanced’
greenhouse effect, leading to increasing world temperature.
It is estimated that atmospheric concentration of carbon dioxide
had increased by 15% in the past 100 years. Along with this, world
temperatures had increased by about 0.5°C over the last century. By
the end of this century, a temperature increase of about 1.5 to 4.5°C is
estimated.
Information Folder (1)—Global Warming 4
Majority of the total global In the 20th century, deforestation
greenhouse gas emissions released large quantities of carbon
(more than 90%) are from dioxide into the atmosphere. The cutting
natural sources and most of of trees means less carbon dioxide will
these are water vapor. Only be absorbed in the process of
about 2% are from photosynthesis. Moreover, additional
man-made sources. carbon dioxide will be released through
the burning of vegetation.
The burning of fossil
fuels has added huge
amount of carbon
dioxide into the Some scientists
atmosphere. believe that the
sun brightens
and fades
periodically. This
will alter global
In the past century, the world temperature.
More CFCs
temperature had slightly Now the sun is
(chlorofluorocarbons) are
increased and led to the brightening and
released into the
warming of the earth. there is a
atmosphere through
However, according to Dr. possibility that
increasing use of aerosols,
Robert C. Balling of Arizona this will cause the
air conditioners and
State University, about 70% of rise of the earth’s
refrigerators by human
that warming occurred before temperature.
beings. Besides, more
1940, i.e. before the effects of
methane is released from
large-scale industrial
the waste dumps.
development.
Information Folder (1)—Global Warming 5
Higher temperatures and more More heavy downpours
heat waves With warmer climate, increase
Global warming, with higher temperatures, in precipitation, especially in
may lead to more intense and frequent heat the type of heavy downpours, is
waves. Heat-related illness and death are expected. In U.K., heavier
increasing. However, if you live in a cold precipitation in winter has
area, higher temperatures may be good to caused the problem of serious
you. The area will become more comfortable flooding in many areas of the
for living. More and better crops might be country.
grown too.
Change in drought
frequency and severity
Change in fire frequency and
Higher temperature changes the
severity
distribution of precipitation.
As climate becomes warmer, droughts
Some areas become drier and
become more common and frequent.
their rainfall becomes
Droughts will increase the frequency and
unreliable. In U.K., for
severity of forest fires. The extensive
example, summer will become
forest fires in Western Europe in 2003 are
drier and a 50% drop in summer
examples of this.
rainfall in the future is
predicted.
Ocean warming, melting glaciers and rising in sea
level
With higher temperatures, ocean is warmer which causes
thermal expansion of water and finally rises in sea level.
Besides, glaciers and ice caps, especially those in polar
areas, melt quicker and cause a rise in sea level. In the 20 th
century, about 15 cm rise in sea level was estimated. More
frequent flooding may be found in low-lying areas.
Information Folder (1)—Global Warming 6
Changes in ecosystems
Habitats and ecosystems of the world
may be affected by global warming. The
original balance may be upset and all
Crops and food supply
In some cold regions, global
living things will be affected. Some
warming may help extend the
plants and animals may not be able to
margins of cultivation and more
adapt to the new environment brought by
crops can be grown. However, it
global warming.
may also bring more droughts to
some important agricultural areas
in the world now. Crop failure may
be more common and food supply
Spread of diseases of the world may be reduced.
Climate sets a constraint for the spread
of many vector-borne diseases, such as
malaria and dengue fever. Increase in
temperature means there may be
changes in the pattern and intensity of
rainfall and humidity. Since most
vector-borne diseases are mainly found
in tropical and subtropical areas, higher
temperature may cause the spread of
these diseases to previously unaffected Change in flood frequency and
areas. Besides, the timing and intensity severity
of disease outbreaks will be changed. Global warming may cause an
increase in precipitation worldwide
and the distribution of precipitation
may be altered too. Some places are
becoming wetter and stormier. In
Bleaching of coral reef U.K., for example, it is predicted that
Warmer water may cause a loss in winter precipitation will increase for
microscopic algae which colour and about 15-35% by 2080. River
nourish living corals. Bleaching of flooding will be more frequent.
coral reefs has already been found in
more than 30 countries of the world.
Information Folder (1)—Global Warming 7
Books:
1. Redfern, D. and Skinner, M. (2003). Advanced Geography. U.K.: Philip Allan
Updates.
2. Warburton, P. (1997). Atmospheric Processes and Human Influence. London:
Collins Education.
3. Waugh, D. (1998). The New Wider World. U.K.: Nelson.
Websites:
1. EPA: Global Warming: Climate
http://yosemite.epa.gov/oar/globalwarming.nsf/content/climate.html
2. Geography in the News
http://www.geographyinthenews.rgs.org/
3. Global Warming: Early Warning Signs
http://www.climatehotmap.org/
4. Global Warming Information Page
http://www.globalwarming.org/
5. Hong Kong Observatory
http://www.hko.gov.hk/contente.htm
