There is no doubt
that the earth is becoming warmer and that it is human activity that has caused
this global warming(這是動名詞,改不了從句) rather than a random but natural phenomenon.
All scientists subscribe to the view
that the increase in the earth's temperature is due to the burning(這是動名詞,改不了從句) of
fossil fuels like coal,natural gas and oil to produce energy.Some byproducts
of this process are called"greenhouse" gases,the most important one
of which is carbon dioxide.Dr Janice Foster explains:" There is a natural
phenomenon that scientists call the 'greenhouse effect'.This is when small
amounts of gases in the atmosphere,like carbon dioxide,methane and water
vapour,trap heat from the sun and therefore warm the earth.Without the
'greenhouse effect',the earth would be about thirty-three degrees Celsius
cooler than it is.So,we need those gases.The problem begins when we add huge
quantities of extra carbon dioxide into the atmosphere.It means that more heat
energy tends to be trapped（不定式作賓語,不好改從句） in the atmosphere causing （現(xiàn)在分詞短語定語=which causes）the global temperature to go up."
We know that the levels of carbon
dioxide have increased greatly over the last 100 to 150 years.It was a
scientist called（過去分詞短語：定語從句=who was）
Charles Keeling,who made accurate measurements of the amount of carbon dioxide
in the atmosphere from 1957 to 1997.He found that between these years the
carbon dioxide in the atmosphere went up from around 315 parts to around 370
parts per million.
All scientists accept this date.They
also agree that it is the burning(這是動名詞：主語,改不了從句) of more fossil fuels that has resulted in this
increase in carbon dioxide.
So how high will the temperature increase go?Dr Janice Foster says that over
the next 100 years the amount of warming(這是動名詞：賓語,改不了從句) could be as low as 1 to 1.5 degree Celsius,but
it could be as high as 5 degrees.
Howevery,the attitude of scientists
towards this rise is completely different.On the one hand,Dr Foster thinks
that the trend which increases the temperature by 5 degrees would be a
catastrophe.She says,"We can't predict the climate well enough to know（不定式結(jié)果狀語：=so well that we know） what to expect(=what we should expect) to know
what to expect(=what we should expect),but it cold be very serious."Other
who agree with her think there may be a rise of several metres in the sea
level,or predict severe storms,floods ,droughts,famines,the spread of species.
On the other hand ,there are those ,like George Hambley ,who are opposed to
this view ,believe that we should not worry about high levels of carbon
dioxide in the air .They predict that any warming(這是動名詞：主語,改不了從句) will be mild with few bad environmental
consequences .In fact ,Hambley states ,"More carbon dioxide is actually a
positive thing .It will make plants grow quicker; crops will produce more;it
will encourage a greater range of animala - all of which will make life for
human beings better."