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  3. There are hidden factors which scientists call "feedback mechanisms". No one knows quite how they will interact with the changin

There are hidden factors which scientists call "feedback mechanisms". No one knows quite how they will interact with the changin

admin2005-06-26  104
问题     There are hidden factors which scientists call "feedback mechanisms". No one knows quite how they will interact with the changing climate. Here’s one example: plants and animals adapt to climate change over centuries. At the current estimate of half a degree centigrade of warming per decade, vegetation(植物)may not keep up. Climatologist James Hansen predicts climate zones will shift toward the poles by 50 to 75 kilometres a year— faster than trees can naturally migrate. Species that find themselves in an unfamiliar environment will die. The 1,000-kilometre-wide strip of forest running through Canada, the USSR and Scandinavia could be cut by half. Millions of dying trees would soon lead to massive forest fires, releasing tons of CO2 and further boosting global warming.
    There are dozens of other possible "feedback mechanisms". Higher temperatures will fuel condensation and increase cloudiness, which may actually damp down global warming. Others, like the "albedo" effect, will do the opposite. The "albedo" effect is the amount of solar energy reflected by the earth’s surface. As northern ice and snow melts and the darker sea and land pokes(戳)through, more heat will be absorbed, adding to the global temperature increase.
    Even if we were to magically stop all greenhouse-gas emissions tomorrow the impact on global climate would continue for decades. Delay will simply make the problem worse. The fact is that some of us are doing quite well the way things are. In the developed world prosperity has been built on 150 years of cheap fossil fuels.
    Material progress has been linked to energy consumption. Today 75 percent of all the world’s energy is consumed by a quarter of the world’s population. The average rich world resident adds about 3. 2 tons of CO2 yearly to the atmosphere, more than four times the level added by each Third World citizen. The US, with just 7 percent of the global population, is responsible for 22 percent of global warming.
It can be inferred from the passage that______.
选项 A、the developing world has decided to increase its energy consumption
B、a third-world citizen adds less than a ton of CO2 yearly to the atmosphere
C、the world climate would soon gain its balance if we stopped greenhouse-gas emissions
D、future prosperity of the world is dependent on cheap fossil fuels
答案B
解析 文章最后一段中指出“The average rich world resident adds about 3．2 tons ofCO2 yearly to the atmosphere， more than four times the level added by each Third World citizen．”由此可知，第三世界国家每人每年向大气中排放的二氧化碳不足3．2吨的1／4，也就是不到1吨的二氧化碳。B项的内容符合文意。A项的内容在文章中没有提及。文章第三段说“Even if we were to magically stop all greenhouse—gas emissions tomorrow the impact on global climate would continue for decades．”可见，即使我们现在停止温室气体的排放，温室气体对全球气候的影响也不会立即消失，而是要持续几十年，地球的气候也不会不久就获得平衡。所以C项不对。D项的内容不符合文意。所以应该选B。
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