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  3. Passage 5 Desertification,drought,and d

Passage 5 Desertification,drought,and d

题库2022-08-02  4
问题 Passage 5Desertification,drought,and despair-that is what global warming has in store for much of Africa.Or so we hear.Emerging evidence is painting a very different scenario,one in which rising temperatures could benefit millions of Africans in the driest parts of the continent.Scientists are now seeing signals that the Sahara desert and surrounding regions are greening due to increasing rainfall.If sustained,these rains could revitalize drought-ravaged regions,reclaiming them for farming communities.This desert-shrinking trend is supported by climate models,which predict are turn to conditions that turned the Sahara into a lush plain some 12,000 years ago.The green shoots of recovery are showing up on satellite images of regions including the Sahel,a semi-desert zone bordering the Sahara to the south that stretches some 2,400 miles.Images taken between 1982 and 2002 revealed extensive re-greening throughout the Sahel,according to a new study in the journal Biogeo sciences.The study suggests huge increases in vegetation in areas including central Chad and western Sudan.The transition may be occurring because hotter air has more capacity to hold moisture,which in turn creates more rain,said Martin Claussen of the Max Planck Institute for Meteorology in Hamburg,Germany.“The water-holding capacity of the air is the main driving force.”Claussen said.While satellite images can’t distinguish temporary plants like grasses that come and go with the rains,ground surveys suggest recent vegetation change is firmly rooted.In the eastern Sahara area of southwestern Egypt and northern Sudan,new trees are flourishing,according to Stefan Kropelin,a climate scientist at the University of Cologne’s Africa Research Unit in Germany.“Before,there was not a single scorpion,not a single blade of grass,”said Kropelin,who has studied the region for two decades.“Now you have people grazing their camels in areas which may not have been used for hundreds or even thousands of years.You see birds,ostriches,coming back,even sorts of amphibians coming back,”he said.“The trend has continued for more than 20 years.It is indisputable.”An explosion in plant growth has been predicted by some climate models.For instance,in 2005 a team led by Reindert Haarsma of the Royal Netherlands Meteorological Institute in De Bilt,the Netherlands,forecast significantly more future rainfall in the Sahel.The study in Geophysical Research Letters predicted that rainfall in the July to September wet season would rise by up to two millimeters a day,by2080.Satellite data shows“that indeed during the last decade,the Sahel is becoming greener,”Haarsma said.Even so,climate scientists do not agree on how future climate change will affect the Sahel—some studies simulate a decrease in rainfall.“This issue is still rather uncertain,”Haarsma said.Max Planck’s Claussen said North Africa is the area of greatest disagreement among climate change modelers.Forecasting how global warming will affect the region is complicated by its vast size and the unpredictable influence of high-altitude winds that disperse monsoon rains,Claussen added.“Half the models follow a wetter trend,and half a drier trend.”What is the role of the sixth paragraph in the development of the topic （　　）A.To make a transition to a new topic.B.To work as a hook to the following paragraphs.C.To provide a contrast to the preceding paragraphs.D.To offer supporting evidence to the preceding paragraph.
选项 A.To make a transition to a new topic.
B.To work as a hook to the following paragraphs.
C.To provide a contrast to the preceding paragraphs.
D.To offer supporting evidence to the preceding paragraph.
答案 D
解析 前面几段讲述了一项新发现，即全球变暖可能使沙漠变绿，第六段列举了几个例子，如灌木长高，可供放牧的地方增多，一些早已消失的动物的回归等，这些例子都能说明沙漠有变绿的迹象，因此D项符合题意。故本题正确答案选D。
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