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afternoon! I’m very glad to stand here and
give you a short speech. My topic today is
global warming.
At present, humans face a serious
challenge. That is global warming.
Increasing global temperatures are causing
a broad range of changes in the world. Sea
levels are rising due to the melting of land
ice.
As you can see, global warming is a
very serious threat to our lives，so it is
important to learn more about it.
Generally,global Warming is caused
by two things. One is man- made, another
is natural causes. One natural cause is the
release of methane gas from arctic tundra
and wetlands. Another natural cause is that
the earth goes through a cycle of climate
change. This climate change usually lasts
about 40,000 years. Man-made causes
probably do the most damage. There are
many man-made causes. Pollution is one
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of the biggest man- made problems.
Pollution comes in many forms. Burning
fossil fuels is one thing that causes
pollution. Fossil fuels ,such as coal or oil.
When they are burned, they give off a
green house gas called carbon dioxide.
Another major man-made cause of
global warming is population increase.
More people mean more food, and more
methods of transportation, right? That
means more methane because there will be
more burning of fossil fuels, and more
agriculture. Another source of methane is
manure. Animals like cows are raised as a
source of food which means more manure
and methane. Another problem with the
increasing population is transportation.
More people mean more cars, and more
cars mean more pollution. Also, many
people have more than one car. In the past
few years, many workers have noted that
the combined effect on climate of
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increases in the concentrations of a large
number of exraust could rival or even
exceed that of the increasing concentration
of carbon dioxide. These exraust,
principally methane and nitrous oxide, are
present at concentrations that are two to
six orders of magnitude lower than that of
carbon dioxide, but are important because,
per molecule, they absorb infrared
radiation much stronger than carbon
dioxide.
Studies have shown that human
activity of this century has increased the
concentrations of atmospheric exraust,
which in turn has elevated global surface
temperatures by blocking the escape of
thermal infrared radiation. Natural climate
variations are masking this temperature
increase, but further additions of exraust
during the next 65 years could double or
even quadruple the present effects, causing
the global average temperature to rise by at
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least 1 °C and possibly by more than 5 °C.
If the rise continues into the twenty-second
century, the global average temperature
may reach higher values than have
occurred in the past 10 million years.
However, assessment of ongoing and
future climate change requires long-term
global monitoring of aerosol properties.
So there is a need and opportunity for
global cooperation in technology
development. Only by doing so that we
can better live in this planet.
Thank you!
Hello, everybody! With the
development of scientific technology, our
life has become the most convenient than
ever before. It is not deniable that we are
in the era filled with digital product. For
example, we put our photos in digital
cameras, we store our assignments and
documents in U-disks, and we place our
favorite songs in MP3 player. They are all
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connected and available through
computers. Computers are adequately used
around the world nowadays, especially
college students, but we also should know
that computers are overused. People spend
so much time working on it, which leads to
series of bad effects.
I’ve been interested in the bad effects
of using computers too much for quite a
long time. I’ve searched on Internet and
looked up related books in library on this
issue. So today I will persuade you to stop
overusing computers for 3 reasons. First, it
will do harm to your health. Second, it is a
waste of time. And third, it will make you
lose some of your abilities.
First, it will do harm to your health.
There are 4 problems at least. According to
Wendy Ghannam and Mats Gyllenberg,
specialists of computers, the low- energy
X-ray and low-frequency electric
radiations can cause the imbalance of
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centered-nerve system. This will cause
headache, sleeplessness and other illness.
It is the first problem. And the second
problem is Carpal Tunnel Syndrome.
According to Tammy Crouch. It is nerve
damage that results from the repetitive
hand motions with constant typing. The
symptoms are intense pain and lessened
motor control in the wrists and hands. The
third one is eyestrain and subsequent
vision. According to Irvin E. Houck Center
for Information Technology, they result
from sitting too close or too far from a
computer screen. The forth problem is the
pain of body, including muscle stress and
back pain. Muscle stress results from
extended periods of computer use without
breaks. Back pain usually comes about
because the computer users don’t sit
properly when working.
So now that we’ve known the
reasons that computers do have harm to
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our body and health, we move on to my
second point------it is a waste of time. I’ve
done a research on 51 students in English
department of our school. I found on
average, that only 16 of their time of
using computer is learning, such as
looking for information doing homework.
The rest 56 is spent on chatting on line,
playing computer games or searching for
the meaningless websites or other things.
I’ve read in the China Daily in my
freshman year that a mother had to lock
the computer because her son overused
computer and caused the declination of his
grade. So most of the people, especially
young people lack the self-controlled
ability, and make it become inevitable.
But it hasn’t over yet. Which brings
me to my third point that overusing
computer make you lose some of your
abilities. You are likely to get lazy and use
pen less than ever after you’ve gotten a
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computer. According to professional
women, a published magazine in China
claimed that overusing computers might
cause reduce of brain function and
therefore recession of memory. Second,
your handwriting will become worse
because of lack use of your pen. Third,
probably you will lose the ability of
controlling the temper. A survey held by
Concord Information Corporation showed
that 10% of their customers would act in
violence simply due to problems of
computer or Internet if they have been
working on it for a long time. They
couldn’t help breaking the screens,
crashing keyboards or mouse when their
PCs wentconclusion, let me summarize my
3 points. First, I told you that overusing
computers do great harm on human bodies.
Second, it is a waste of time. Third, it
makes you lose some of your abilities. So
overusing computers is really harmful. In
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closing, I want to declare one thing, that is:
I’m not asking you not to use computers
anymore. We have to use it, because it is
necessary, a need, a must, for every one of
us. But when we use it, we’d better ask
ourselves, whether I use it properly,
whether I overuse it. Thank you.
各位读友大家好，此文档由网络收集而来，欢迎您下载，谢谢


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