【题目】Beijing had its coldest morning in almost 40 years and its biggest snowfall since 1951. Britain is suffering through its longest cold snap (寒潮since 1981. And freezing weather is hitting the US south.

Whatever happened to global warming?

Such weather doesn't seem to fit with warnings from scientists that the earth is warming because of greenhouse gases. But experts say the coldness doesn't deny global warming at allit's just a blip in the long-term heating trend.

"It's part of natural variability(变化性)," said Gerald Meehl, a senior scientist at the National Centre for Atmospheric Research in Boulder, Colo. With global warming, he said"We'll still have record cold temperatures. We'll just have fewer of them.

Scientists say man-made climate change does have the potential to cause more frequent and more severe weather extremes, such as heat waves, storms, floods, droughts and even coldness. But experts did not connect the current cold weather to climate change.

So what is going on?

"We basically have seen just a big outbreak of Arctic air over populated areas of the Northern Hemisphere"Arndt said. In the atmosphere, large rivers of air travel roughly west to east around the globe between the Arctic and the tropics. But recently, this air flow has become bent into a pronounced (明显的z pattern, moving from north and south. If you live in a place where it brings air up from the south, you will get warm weather. In fact, record highs were reported this week in Washington state and Alaska.

But in some other unlucky parts of the globe, Arctic air is moving down from the north. And that's how you get the low temperature in Beijing, and 18 inches of snow in parts of Britain, where a member of Parliament who said the snow "clearly indicates a cooling trend " was laughed at by colleagues.

The z pattern arises naturally from time to time, but it is not clear why it's so strong right now, said Michelle Heureux, a meteorologist at the Climate Prediction Center of the National Oceanic and Atmospheric Administration. The center says the pattern should begin to weaken in a week or two.

1 Many areas are suffering low temperature except __________.

A. Beijing

B. Washington state and Alaska

C. the US south

D. Britain

2 The underlined word blip in Paragraph 3 means __________.

A. temporary phenomenon

B. abnormal phenomenon

C. common phenomenon

D. rare phenomenon

3 From the text, it can be learned that __________.

A. global warming trend has proved wrong

B. there will be less coldness in the future

C. the z pattern Arctic air flow seldom happens

D. scientists haven't found out the reason of coldness

4 The present coldness is probably caused by __________.

A. climate change

B. Arctic air traveling west to east

C. the z pattern Arctic air flow

D. the cooling trend

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