题目内容
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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 temperature and of atmospheric (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 (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 9F (5℃), 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 aprofusion of plant life whose buried remains produced a large fraction of the coal deposits that am being brought to the surface and burned today.
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 temperature and of atmospheric
(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
(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 9F (5℃), 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 aprofusion of plant life whose
buried remains produced a large fraction of the coal deposits that am being brought to the surface
and burned today.
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