[问答] 36套 EX35长阅读 [复制链接]

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电梯直达

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发表于 2012-9-28 00:51:54 |只看该作者 |倒序浏览

Aided by the recent ability to analyze samples of air
trapped in glaciers, scientists now have a clearer idea of
the relationship between atmospheric composition and
global temperature change over the past 160,000 years.
In particular, determination of atmospheric composition
during periods of glacial expansion and retreat (cooling
and warming) is possible using data from the 2,000-meter
Vostok ice core drilled in Antarctica. The technique
involved is similar to that used in analyzing cores of
marine sediments, where the ratio of the two common
isotopes of oxygen,
18
O and
16
O, accurately reflects past
temperature changes. Isotopic analysis of oxygen in the
Vostok core suggests mean global temperature
fluctuations of up to 10 degrees centigrade over the past
160,000 years.
Data from the Vostok core also indicate that the
amount of carbon dioxide has fluctuated with temperature
over the same period: the higher the temperature, the
higher the concentration of carbon dioxide and the lower
the temperature, the lower the concentration. Although
change in carbon dioxide content closely follows change
in temperature during periods of deglaciation, it
apparently lags behind temperature during periods of
cooling. The correlation of carbon dioxide with
temperature, of course, does not establish whether
changes in atmospheric composition caused the warming
and cooling trends or were caused by them.
The correlation between carbon dioxide and
temperature throughout the Vostok record is consistent
and predictable. The absolute temperature changes,
however, are from 5 to 14 times greater than would be
expected on the basis of carbon dioxide‘s own ability to
absorb infrared radiation, or radiant heat. This reaction
suggests that, quite aside from changes in heat-trapping
gases, commonly known as greenhouse gases, certain
positive feedbacks are also amplifying the temperature
change. Such feedbacks might involve ice on land and sea,
clouds, or water vapor, which also absorb radiant heat.
Other data from the Vostok core show that methane
gas also correlates closely with temperature and carbon
dioxide. The methane concentration nearly doubled, for
example, between the peak of the penultimate glacial
period and the following interglacial period. Within the
present interglacial period it has more than doubled in just
the past 300 years and is rising rapidly. Although the
concentration of atmospheric methane is more than two
orders of magnitude lower than that of carbon dioxide, it
cannot be ignored: the radiative properties of methane
make it 20 times more effective, molecule for molecule,
than carbon dioxide in absorbing radiant heat. On the
basis of a simulation model that climatological
researchers have developed, methane appears to have
been about 25 percent as important as carbon dioxide in
the warming that took place during the most recent glacial
retreat 8,000 to 10,000 years ago.
(445 words)
其中的问题4：

4. According to the passage, which of the following
statements best describes the relationship between
carbon dioxide and global temperature?
(A) Carbon dioxide levels change immediately
   in response to changes in temperature.
(B) Carbon dioxide levels correlate with global
   temperature during cooling periods only.
(C) Once carbon dioxide levels increase, they
   remain high regardless of changes in global
   temperature.
(D)Carbon dioxide levels increase more quickly
   than global temperature does.
(E) During cooling periods, carbon dioxide levels
   initially remain high and then decline.

尚杰的答案里面写着
it apparently lags behind temperature during periods of cooling；答案：E
但是从这个lag behind 怎么就推出先保持再下降呢？
哪里题了温度的变化过程吗？不解啊！
难道是那个period of cooling，说明了温度在下降？
望大牛指导啊！

[问答] 36套 EX35长阅读 [复制链接]

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