A nearly ice-free Arctic Ocean in the summer may happen three times sooner than scientists have assessed. New research says the Arctic might lose most of its ice cover in summer in as few as 30 years instead of the end of the century.

The amount if the Arctic Ocean covered by ice at the end of summer by then could be only about 1million square kilometers. That's compared to today’s ice extent of 4.6 million square kilometers. So much more open water could be a boon for shipping and for extracting minerals and oil from the seabed, but it raises the question of ecosystem change.

While the Intergovemmental Panel on Climate Change in 2007 assessed what might happen in the Arctic in the future based on results from more than a dozen global climate models, two researchers said that dramatic drops in the extent of ice at the end of summer in 2007 and 2008 called for a different approach.

.Out of the 23 models now available, the new predictions are based on the six most suited fo rassessing sea ice, according to Muyin Wang, a University of Washington climate scientist, and James Overland, an oceanographer. Wang and Overland sought models that best matched what has actually happened in recent years, because, "if a model can't do today's conditions well, how can you O:ust its future predictions? " Wang says.

"In recent years the combination of unusual warm temperatures from natural causes and the globalwarming signal have worked together to provide an earlier summer sea-ice loss than was predicted whenscientists considered the effects from human-caused carbon dioxide alone, "says Overland.

Scientists don't expect the Arctic to be totally ice free, figuring that ice still will be found along northern Canada and Greenland where powerful winds sweeping across the Arctic Ocean force ice layers to slide on topof each other, making for a very thick ice cover.

1. What does the underlined word "boon" mean?

A. Bad.                B. Useful.

C. Dangerous.        D. Generous.

2. Which statement do the researchers seem to agree with?

A.That the ice in the Arctic will disappear completely in 30 years.

B.That there will be a very thick ice cover in northern Canada

C. That the sea-ice loss was the effect of the unusual climate change.

D.That the temperature will be very low in the future because of the sea ice.

3. How many models were the new prediction made by Muyin Wang and James Overland based on?
C. 12.                    D. 23.

4.  The author writes this passage to tell readers _,
A. how to prevent global warming

B. the cause of global warming

C. the new research about the Arctic sea ice

D. how to do research with models

 答案
 篇章导读
 新的研究表明：在30年后的夏季，北极的大多数冰将会消失。

1．D词义推测题。通读全文可知，文章主要讲述了北极的大多数的冰将会在30年左右消失，那时海平面上升，水域开阔，对于海运来说，应是慷慨的（generous）。
2．B推理判断题。根据文章最后一段的“Scientists don'texpect the Arctic to be totally ice free, figuring that icestill...and Greenland where powerful winds...for a very thickice cover.”可知，科学家们认为冰不会完全消失，冰将会在风力的作用下形成一个厚冰盖。
3．B细节理解题。根据文章第四段第一句可知，这个预测是根据6个全球气候模型得出的结果。
4．C主旨大意题。通读全文可知，本文主要的目的是向读者讲述一个最新的关于北极的冰的科学研究。