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Effects of Environmental Pollution If pollution continues to increase at the present rate, formation of aerosols (浮质) in the atm

admin2009-06-15  78
问题 Effects of Environmental Pollution
If pollution continues to increase at the present rate, formation of aerosols (浮质) in the atmosphere will cause the onset (开始) of an ice age in about fifty year’s time. This conclusion reached by Dr S. I. Rasoo1 and Dr S. H. Scheider of the United States Goddard Space Flight Center, answer the apparently conflicting questions of whether an increase in the carbon dioxide (二氧化碳) content of the atmosphere will cause the Earth warm up or increasing the aerosol question is dominant.
Two specters haunting conservationists have been the prospect that environmental pollution might lead to the planet’s becoming unbearably hot or cold. One of these ghosts has now been laid, because it seems that even an increase in the amount of carbon dioxide in the atmosphere to eight times its present value will produce an increase in temperature of only 2℃, which would take place over several thousand years. But the other problem now looms larger than ever.
Aerosols are collection of small liquid or solid particles dispersed in air or some other medium. The particles are all so tiny that each is composed of only a few hundred atoms. Because of this they can float in the air for a very long time. Perhaps the most commonly experienced aerosol is industrial smog (烟雾) of the kind that plagued London in the 1950s and is an even greater problem in Los Angeles today. These collections of aerosols reflect the Sun’s heat and thereby cause the Earth to cool.
Dr Rasoo1 and Dr Schneider have calculated the exact effect of a dust aerosol layer just above the Earth’s surface in the temperature of the planet. As the layer builds up, the present delicate balance between the amount of heat absorbed from the Sun and the amount radiated from the Earth is disturbed. The aerosol layer not only reflects much of the Sun’s light but also transmits the infrared (红外线) radiation from below. So, while the heat input to surface drops, the loss of heat remains high until the planet cools to a new balanced state.
Within fifty years, if no steps are taken to stop the spread of aerosols in the atmosphere, a cooling of the Earth by as much as 3.5~C seems inevitable. If that lasts for only a few years it would start another ice age, and because the growing ice caps at each pole would themselves reflect much of the Sun’s radiation it would probably continue to develop even if the aerosol layer were destroyed.
The only bright spot in this gloomy forecast lies in the hope expressed by Dr Rasoo1 and Dr Schneider that nuclear powder may replace fossil fuels in time to prevent the aerosol content of atmosphere from becoming critical.
选项 A、warm weather
B、hot weather
C、a new ice age
D、a new iceberg
答案C
解析 该问题是总结性的，对于这样的问题，可以放在最后做，也可以借助文章标题和文章核心词，对选项——筛选得出答案。C和D的相似暗示答案可能出现在它们中。而ice age在文章中多处出现，所以判断C是答案。
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