Passage 5
Desertification,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.”
According to the first paragraph,global warming is supposed to have the following impacts on Africa EXCEPT（ ）.
根据第一段，Desertification,drought,and despair-that is what global warming has in store for much of Africa.Or so we hear.沙漠化、干旱和绝望——这些都是全球变暖给非洲大部分地区带来的后果。因此只有D项不属于全球化带给非洲的影响。故本题正确答案选D。
下列关于公司的表述，正确的是（）
以下各项列举了我国常见气象灾害与其发生地区的对应关系，其中正确的一项是（）
根据电视收视率调査，看体育节目的观众中青年人比中老年人要多。
由此可推断出（）
—种海洋蜗牛产生的毒素含有多种蛋白，把其中的一种给老鼠注射后，会使有两星期大或更小的老鼠陷入睡眠状态，而使大一点的老鼠躲藏起来。当老鼠受到突然的严重威胁时，非常小的那些老鼠的反应是呆住，而较大的那些老鼠会逃跑。
以上陈述的事实最有力地支持了以下哪项假说？（）
疾病控制中心对某校髙中三个年级的学生进行抽样做视力状况调查，抽样的方法为分层抽样（按比例抽样），若高中一、二、三年级学生人数分别为626、703、780，样本容量为84，则应从离二年级抽样的学生人数为多少？（）
