请教一道阅读题，36套ex35冰川期温度与大气关系

loly_heUID: 3242491

36套 Exercise35


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, 18O and 16O, 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.


5. It can be inferred from the passage that a long-term
decrease in the concentration of carbon dioxide in
the Earth‘s atmosphere would
(A) increase methane concentration in the
Earth‘s atmosphere
(B) accompany a period of glaciation
(C) encourage the formation of more oxygen
isotopes in the Earth‘s atmosphere
(D) promote the formation of more water in the
Earth‘s global environment
(E) increase the amount of infrared radiation
absorbed by the Earth‘s atmosphere

6. The passage suggests that when the methane
concentration in the Earth‘s atmosphere
decreases, which of the following also
happens?
(A) Glaciers melt faster.
(B) The concentration of carbon dioxide increases.
(C) The mean global temperature decreases.
(D) Carbon dioxide absorbs more radiant beat
(E) More clouds form in the Earth‘s atmosphere



这两题按答案来看，是认定大气成分能够决定地球温度，但是文中并没有明确的给出这种关系，只在蓝色部分给出了“两者同时存在”的关系。
而且文中还有“does not establish whether changes in atmospheric composition caused the warming and cooling trends or were caused by them.” 说明两者的关系是没有定论的，那为什么会有这样的答案呢？


请各位大侠解惑~~

苏梳眠UID: 2717864

9104的旧题。
可以去精华区找找解释和翻译。

晓之风UID: 3342832

我也迷茫中啊！楼主要是指导怎么解，告诉下我！