单选题Which of the following is the best title for the passage ?A A computer modelB Studies show ice melted equally in the North and the South during the ice ageC Most of the ice melted in the Northern hemisphere during the 30,000-year long ice ageD A survey

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New research from NASA scientists suggests emissions of black soot after the way sunlight re- flects off snow.According to a computer simulation,black soot may be responsible for 25 percent of observed global warming over the past century. Soot in the higher latitudes（维度）of the Earth,where ice is more common , absorbs more of the sun's energy and warmth than an icy,white background. Dark-colored black carbon,or soot, absorbs sunlight,while lighter colored ice reflects sunlight.
Soot in areas with snow and ice may play an important role in climate change.Also,if snow and ice covered areas begin melting,the warming effect increase,as the soot becomes more con-centrated on the snow surface.“This provides a positive feedback,as glaciers and ice sheets melt, they tend to get even dirtier.”said Dr. James Hansen,a researcher at NASA's Goddard Institute for Space Studies,New York.
Hansen found soot's effect on snow albedo（反照率）,which may be contributing to trends to-ward early springs in the Northern Hemisphere,such as thinning Arctic sea ice and melting glac-iers permafrost. Soot also is believed to play a role in changes in the atmosphere above the oceans and land.
“Black carbon reduces the amount of energy reflected by snow back into space,thus heating the snow surface more than if there were no black carbon,”Hansen said. Soot's increased absorp-tion of solar energy is especially effective in warming the world's climate.“ This forcing is unusual-ly effective,causing twice as much global warming as a carbon-dioxide forcing of the same magni-tude.”Hansen noted.
Hansen cautioned,although the role of soot in altering global climate is substantial,it does not alter the fact that greenhouse gases are the primary cause of climate warming during the past century .Such gases are expected to be the largest climate forcing for the rest of the century.
The researchers found that observed warming in the Northern Hemisphere was large in the winter and spring at middle and high latitudes. These observations were coherent with the researchers' climate model situations,which showed some of the largest warming effects occurred when there were heavy snow cover and sufficient sunlight.

The largest warming effects happened in the Northern Hemisphere with_____.
A: thin sea ice and insufficient sunlight
B: light、 snow cover and sufficient sunlight
C: heavy snow cover and sufficient sunlight
D:.thick sea ice and sufficient sunlight

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第一篇

Arctic Melt

Earth’s North and South Poles are famous for being cold and icy.Last year,however,the amnount of ice
in the Arctic Ocean（北冰洋）fell to a record low.
Normally,ice builds in Arctic waters around the North Pole each winter and shrinks（缩小）during the
summer. But for many years,the amount of ice left by the end of summer has been declining.
Since 1979,each decade has seen an 11.4 percent drop in end?of-summer ice cover. Between 1981 and
2000,ice in the Arctic lost 22 percent of its thickness,becoming I.13 meters thinner.
Last summer,Arctic sea ice reached its thinnest levels yet.By the end of summer 2007,the ice had
shrunk to cover just 4.2 million square kilometers.That's 38 percent less area than the average cover at that
time of year. And it's a very large 23 percent below the previous record low,which was set just 2 years ago.
This continuing trend has made scientists concerned.
There may be several reasons for the ice melt, says Jinlun Zhang, an oceanographer（海洋学家）at the
University of Washington at Seattle.Unusually strong winds blew through the Arctic last summer. The winds
pushed much of the ice out of the central Arctic,leaving a large area of thin ice and open water.
Scientists also suspect that fewer clouds cover the Arctic now than in the past.Clearer skies allow more
sunlight to reach the ocean.The extra heat warms both the water and the atmosphere.In parts of the Arctic
Ocean last year,surface temperatures were 3.5℃warmer than average and 1.5℃warmer than the previous
record high.
With both air and water getting warmer,the ice is melting from both above and below. In some parts of
the Beaufort Sea,north of Alaska and western Canada,ice that measured 3.3 meters thick at the beginning
of the summer measured just 50 centimeters by season's end.
The new measurements suggest that melting is far more severe than scientists have seen by just looking
at ice covcrfrom above,says Donald K. Perovich,a geophysicist at the U.S.Army Cold Regions Research
and Engineering Laboratory in Hanover,N.H.
Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.

By the end of summer 2007 the ice cover in the Arctic was ________.
A:4.2 million square kilometers
B:11.4 million square kilometers
C:1.13 million square kilometers
D:38 million square kilometers

共用题干
New research from NASA scientists suggests emissions of black soot after the way sunlight re- flects off snow.According to a computer simulation,black soot may be responsible for 25 percent of observed global warming over the past century. Soot in the higher latitudes（维度）of the Earth,where ice is more common , absorbs more of the sun's energy and warmth than an icy,white background. Dark-colored black carbon,or soot, absorbs sunlight,while lighter colored ice reflects sunlight.
Soot in areas with snow and ice may play an important role in climate change.Also,if snow and ice covered areas begin melting,the warming effect increase,as the soot becomes more con-centrated on the snow surface.“This provides a positive feedback,as glaciers and ice sheets melt, they tend to get even dirtier.”said Dr. James Hansen,a researcher at NASA's Goddard Institute for Space Studies,New York.
Hansen found soot's effect on snow albedo（反照率）,which may be contributing to trends to-ward early springs in the Northern Hemisphere,such as thinning Arctic sea ice and melting glac-iers permafrost. Soot also is believed to play a role in changes in the atmosphere above the oceans and land.
“Black carbon reduces the amount of energy reflected by snow back into space,thus heating the snow surface more than if there were no black carbon,”Hansen said. Soot's increased absorp-tion of solar energy is especially effective in warming the world's climate.“ This forcing is unusual-ly effective,causing twice as much global warming as a carbon-dioxide forcing of the same magni-tude.”Hansen noted.
Hansen cautioned,although the role of soot in altering global climate is substantial,it does not alter the fact that greenhouse gases are the primary cause of climate warming during the past century .Such gases are expected to be the largest climate forcing for the rest of the century.
The researchers found that observed warming in the Northern Hemisphere was large in the winter and spring at middle and high latitudes. These observations were coherent with the researchers' climate model situations,which showed some of the largest warming effects occurred when there were heavy snow cover and sufficient sunlight.

What is the main cause of climate warming during the past century?
A: Soot.
B: Snow.
C: Greenhouse gases.
D:.Wind.

共用题干
第一篇

Arctic Melt

Earth’s North and South Poles are famous for being cold and icy.Last year,however,the amnount of ice
in the Arctic Ocean（北冰洋）fell to a record low.
Normally,ice builds in Arctic waters around the North Pole each winter and shrinks（缩小）during the
summer. But for many years,the amount of ice left by the end of summer has been declining.
Since 1979,each decade has seen an 11.4 percent drop in end?of-summer ice cover. Between 1981 and
2000,ice in the Arctic lost 22 percent of its thickness,becoming I.13 meters thinner.
Last summer,Arctic sea ice reached its thinnest levels yet.By the end of summer 2007,the ice had
shrunk to cover just 4.2 million square kilometers.That's 38 percent less area than the average cover at that
time of year. And it's a very large 23 percent below the previous record low,which was set just 2 years ago.
This continuing trend has made scientists concerned.
There may be several reasons for the ice melt, says Jinlun Zhang, an oceanographer（海洋学家）at the
University of Washington at Seattle.Unusually strong winds blew through the Arctic last summer. The winds
pushed much of the ice out of the central Arctic,leaving a large area of thin ice and open water.
Scientists also suspect that fewer clouds cover the Arctic now than in the past.Clearer skies allow more
sunlight to reach the ocean.The extra heat warms both the water and the atmosphere.In parts of the Arctic
Ocean last year,surface temperatures were 3.5℃warmer than average and 1.5℃warmer than the previous
record high.
With both air and water getting warmer,the ice is melting from both above and below. In some parts of
the Beaufort Sea,north of Alaska and western Canada,ice that measured 3.3 meters thick at the beginning
of the summer measured just 50 centimeters by season's end.
The new measurements suggest that melting is far more severe than scientists have seen by just looking
at ice covcrfrom above,says Donald K. Perovich,a geophysicist at the U.S.Army Cold Regions Research
and Engineering Laboratory in Hanover,N.H.
Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.

It can be learned from the last sentence that _________.
A:the ice melt in the Arctic may never stop
B:scientists are trying hard to stop the ice melt in the Arctic
C:scientists are delighted to find out what is going on in the Arctic
D:the warming trend in the Arctic can be reversed in the near future

共用题干
第一篇

Arctic Melt

Earth’s North and South Poles are famous for being cold and icy.Last year,however,the amnount of ice
in the Arctic Ocean（北冰洋）fell to a record low.
Normally,ice builds in Arctic waters around the North Pole each winter and shrinks（缩小）during the
summer. But for many years,the amount of ice left by the end of summer has been declining.
Since 1979,each decade has seen an 11.4 percent drop in end?of-summer ice cover. Between 1981 and
2000,ice in the Arctic lost 22 percent of its thickness,becoming I.13 meters thinner.
Last summer,Arctic sea ice reached its thinnest levels yet.By the end of summer 2007,the ice had
shrunk to cover just 4.2 million square kilometers.That's 38 percent less area than the average cover at that
time of year. And it's a very large 23 percent below the previous record low,which was set just 2 years ago.
This continuing trend has made scientists concerned.
There may be several reasons for the ice melt, says Jinlun Zhang, an oceanographer（海洋学家）at the
University of Washington at Seattle.Unusually strong winds blew through the Arctic last summer. The winds
pushed much of the ice out of the central Arctic,leaving a large area of thin ice and open water.
Scientists also suspect that fewer clouds cover the Arctic now than in the past.Clearer skies allow more
sunlight to reach the ocean.The extra heat warms both the water and the atmosphere.In parts of the Arctic
Ocean last year,surface temperatures were 3.5℃warmer than average and 1.5℃warmer than the previous
record high.
With both air and water getting warmer,the ice is melting from both above and below. In some parts of
the Beaufort Sea,north of Alaska and western Canada,ice that measured 3.3 meters thick at the beginning
of the summer measured just 50 centimeters by season's end.
The new measurements suggest that melting is far more severe than scientists have seen by just looking
at ice covcrfrom above,says Donald K. Perovich,a geophysicist at the U.S.Army Cold Regions Research
and Engineering Laboratory in Hanover,N.H.
Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.

The Beaufort Sea mentioned in Paragraph 7 is an example to show_________.
A:how acetirate the new measurements are
B:how thick the ice is in it
C:how serious the problem of the ice melt in the Arctic is
D:how dangerous it is to travel to it