高分班测试题(A)

环球雅思连锁学校 www.IELTS.com.cn 高分班入学测试卷

Questions 28-32

Reading Passage 3 has six sections A-F.

Choose the correct heading for sections A-E from the list of headings below. Write the correct number i-x in boxes 28-32 on your answer sheet.

List of Headings i Contrary indications ii Europe?s Alpine glaciers iii Growing consensus on sea level iv Ice cap observation v Causes of rising sea levels vi Panel on Climate Change vii Sea level monitoring difficulties viii Group response to alarming predictions ix Stockholm and Scandinavia x The world 130,000 years ago 28 Section A 29 Section B 30 Section C

31 Section D 32

Section E

Rising Sea Levels

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环球雅思连锁学校 www.IELTS.com.cn 高分班入学测试卷 A

During the night of 1st February 1953, a deadly combination of winds and tide raised the level of the North Sea, broke through the dykes which protected the Netherlands and inundated farmland and villages as far as 64 km from the coast, killing thousands. For people around the world who inhabit low-lying areas, variations in sea levels are of crucial importance and the scientific study of oceans has attracted increasing attention. Towards the end of the 1970s, some scientists began suggesting that global warming could cause the world?s oceans to rise by several metres. The warming, they claimed, was an inevitable consequence of increasing carbon dioxide in the atmosphere which acted like a greenhouse to trap heat in the air. The greenhouse warming was predicted to lead to rises in sea levels in a variety of ways. Firstly, heating the ocean water would cause it to expand. Such expansion might be sufficient to raise the sea level by 300mm in the next 100 years. Then there was the observation that in Europe?s Alpine valleys glaciers had been shrinking for the past century. Meltwater from the mountain glaciers might have raised the oceans 50mm over the last 100 years and the rate is likely to increase in future. A third threat is that global warming might cause a store of frozen water in Antarctica to melt which would lead to a calamitous rise in sea level of up to five metres. B

The challenge of predicting how global warming will change sea levels led scientists of several disciplines to adopt a variety of approaches. In 1978 J H Mercer published a largely theoretical statement that a thick slab of ice covering much of West Antarctica is inherently unstable. He suggested that this instability meant that, given just 5 degrees Celsius of greenhouse warming in the south polar region, the floating ice shelves surrounding the West Antarctic ice sheet would begin to disappear. Without these buttresses the grounded ice sheet would quickly disintegrate and coastlines around the world would be disastrously flooded. In evidence Mercer pointed out that between 130,000 and 110,000 years ago there had been just such a global warming as we have had in the past 20,000 years since the last ice age. In the geological remains of that earlier period there are indications that the sea level was five metres above the current sea level-just the level that would be reached if the West Antarctic ice sheet melted. The possibility of such a disastrous rise led a group of American investigations to form SeaRISE (Sea-level Response to Ice Sheet Evolution) in 1990. SeaRISE reported the presence of five active “ice streams” drawing ice from the interior of West Antarctica into the Ross Sea. They stated that these channels in the West Antarctic ice sheet “may be manifestations of collapse already under way.” C

But doubt was cast on those dire warnings by the use of complex computer models of climate. Models of atmospheric and ocean behaviour predicted that greenhouse heating would cause warmer, wetter air to reach Antarctica, where it would deposit its moisture as snow. Thus, the sea ice surrounding the continent might even expand causing sea levels to drop. Other observations have caused scientists working on Antarctica to doubt that sea levels will be pushed upward several metres by sudden melting. For example, glaciologists have discovered that one of the largest ice streams stopped moving about 130 years ago. Ellen Mosley-Thompson, questioning the SeaRISE theory, notes that ice stresms “seem to start and stop, and nobody really knows why.” Her own measurements of the rate of snow accumulation near the South Pole show that snowfalls have increased substantially in recent decades as global temperature has increased.

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环球雅思连锁学校 www.IELTS.com.cn 高分班入学测试卷 D

Most researchers are now willing to accept that human activities have contributed to global warming, but no one can say with any assurance whether the Antarctic ice cap is growing or shrinking in response. A satellite being planned by the National Aeronautics and Space Administration will use laster range finders to map changes in the elevation of the polar ice caps, perhaps to within 10 millimetres, and should end the speculation. E

Whatever the fate of the polar ice caps may be, most researchers agree that the sea level is currently rising. That, however, is difficult to prove. Tide gauges in ports around the world have been measuring sea levels for decades but the data are flawed because the land to which the gauges are attached can itself be moving up and down. In Stockholm the data from the sea level gauge show the sea level to be falling at four millimeters a year, but that is because all Scandinavia is still rebounding after being crushed by massive glaciers during the last ice age. By contrast, the gauge at Honolulu, which is more stable, shows the sea level to be rising at a rate of one and a half millimeters a year. Unstable regions cannot be omitted from the data because that would eliminate large areas of the world. Most of the eastern seaboard of North America is still settling after a great ice sheet which covered Eastern Canada 20,000 years ago tilted it up. And then there is buckling occurring at the edges of the great tectonic plates as they are pressed against each other. There is also land subsidence as oil and underground water is tapped. In Bangkok, for example, where the residents have been using groundwater, land subsidence makes it appear as if the sea has risen by almost a metre in the past 30 years. F

Using complex calculations on the sea level gauge data, Peltier and Tushingham found that the global sea level has been rising at a rate of 2mm a year over the past few decades. Confirmation came from the TOPEX satellite which used radar altimeters to calculate changes in ocean levels. Steven Nerem, working on the TOPEX data, found an average annual sea level rise of 2mm which is completely compatible with the estimates that have come from 50 years of tide gauge records. The key question still facing researchers is whether this trend will hold steady or begin to accelerate in response to a warming climate. The Intergovernmental Panel on Climate Change gives the broad prediction for the next century of a rise between 200mm and I metre.

Questions 33-40

Complete each sentence with the correct ending A-L from the below. Write the correct letter A-L in boxes 33-40 on your answer sheet.

33 The Dutch dykes were broken

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34 Without ice shelves, West Antarctic ice covers would contract 35 Mercer predicted a 5-metre sea- level rise

36 SeaRISE believed the collapse of Antarctic ice had begun

环球雅思连锁学校 www.IELTS.com.cn 高分班入学测试卷 37 Mosley-Thompson doubted the SeaRISE theory A B C D E F G H I J K L

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38 Doubts over Antarctica?s trends will soon be settled 39 Stockholm?s tide gauge shows a fall in sea level

40 At Bangkok the sea appears to have risen one metre in 30 years

because the land mass is rising. because ice stream flows are variable and unpredictable. because Europe?s alpine valley glaciers were shrinking. because of a combination of wind and high tide. because of geological evidence of an earlier rise. because satellites will take laser measurements. because the temperature had risen five degrees in 1978. because there were five active streams of ice. because they are inherently unstable. because use of groundwater has caused the land to sink. because warmer, wetter air would increase snowfall. because we cannot predict the rate of change.