Question 40-50
Scientists have discovered that for the last 160,000 years, at least, there has
been a consistent relationship between the amount of carbon dioxide in the air and
the average temperature of the planet. The importance of carbon dioxide in
regulating the Earth's temperature was confirmed by scientists working in eastern
(5) Antarctica. Drilling down into a glacier, they extracted a mile-long cylinder of ice
from the hole. The glacier had formed as layer upon layer of snow accumulated year
after year. Thus drilling into the ice was tantamount to drilling back through time.
The deepest sections of the core are composed of water that fell as snow
160,000 years ago. Scientists in Grenoble, France, fractured portions of the core and
(10)measured the composition of ancient air released from bubbles in the ice.
Instruments were used to measure the ratio of certain isotopes in the frozen water to
get an idea of the prevailing atmospheric temperature at the time when that
particular bit of water became locked in the glacier.
The result is a remarkable unbroken record of temperature and of atmospheric
(15)levels of carbon dioxide. Almost every time the chill of an ice age descended on the
planet, carbon dioxide levels dropped. When the global temperature dropped 9°F (5 °C),
carbon dioxide levels dropped to 190 parts per million or so. Generally, as each
ice age ended and the Earth basked in a warm interglacial period, carbon dioxide
levels were around 280 parts per million. Through the 160,000 years of that ice
(20)record, the level of carbon dioxide in the atmosphere fluctuated between 190 and
280 parts per million, but never rose much higher-until the Industrial Revolution
beginning in the eighteenth century and continuing today.
There is indirect evidence that the link between carbon dioxide levels and
global temperature change goes back much further than the glacial record. Carbon
(25) dioxide levels may have been much greater than the current concentration during the
Carboniferous period, 360 to 285 million years ago. The period was named for a
profusion of plant life whose buried remains produced a large fraction of the coal
deposits that are being brought to the surface and burned today.
【題組】44. According to the passage, Grenoble, France, is the place where
(A) instruments were developed for measuring certain chemical elements
(B) scientists first recorded atmospheric levels of carbon dioxide
(C) scientists studied the contents of an ice core from Antarctica
(D)
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