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  3. Cleaning up our air may have made us healthier. A new analysis shows that the number of storms falls when pollution rises, and i

Cleaning up our air may have made us healthier. A new analysis shows that the number of storms falls when pollution rises, and i

admin2017-11-08  39
问题    Cleaning up our air may have made us healthier. A new analysis shows that the number of storms falls when pollution rises, and increases when pollution drops. Further tightening of present pollution controls " could reduce aerosols (气溶胶；悬浮颗粒) so quickly that we have record numbers of tropical storms for the next decade or two" , says Nick Dunstone of the Met Office
   Hadley Centre in Exeter, UK.
   Earlier studies found no connection between storm numbers and aerosols’ ability to cool the surface by scattering light in the open air. But aerosols also increase the brightness and lifetime of low-level marine clouds. When Nick Dunstone of the Met Office Hadley Centre in Exeter, UK, added this effect into his climate models, the simulated clouds cooled the surface more than expected. Historically, this cooling effect has been strongest in the north Atlantic.
   Cooling the north Atlantic reduces the energy available to power hurricanes. It also shifts rising and falling air currents further south, increasing wind shear in the Atlantic hurricane nursery. This extra wind shear tears nascent storms apart before they can gain strength. In this way, Dunstone says, changes in aerosol emissions appear to drive cyclical variations in north Atlantic tropical storms. These variations have long been attributed to natural variations in ocean circulation.
   Throughout the 20th century, aerosol emissions increased with industrialization and decreased in economic slumps. Tropical storms were frequent from the 1930s through to the 1950s, but rarer in the better economic times of the 1960s to mid-1990s. Then pollution controls reduced aerosol levels, and Atlantic hurricanes came roaring back, with 19 in 1995, a record 28 in 2005, and 19 in each of the past three years.
   Dunstone expects the increase to continue for another two decades. After that, global warming may begin to reduce the number of tropical storms, by warming the air and thus reducing the temperature difference between the sea surface and the atmosphere. It is not clear whether aerosols affect the intensity of storms.
What can we learn from the first two paragraphs?
选项 A、The number of storms is inversely proportional to pollution index.
B、The number of storms is related to aerosols’ ability to cool the surface.
C、Aerosols increase the brightness and lifetime of marine clouds.
D、Aerosols cool the surface by gathering light in the open air.
答案A
解析 根据题干，该题应定位到本文的前两段。A选项中inversely proportional意为“成反比”，也就是说风暴数量和污染指数是成反比的，这正是文章的中心思想，在第一段中也有详细表述，所以A选项正确。B选项指出风暴的数量是和气溶胶冷却海洋表面空气的能力相关的。而第二段第一句指出气溶胶通过散射户外光线来冷却海洋表面空气，而早期的研究并未发现风暴的数量和气溶胶的这种能力有关系。所以B选项不对。C选项“气溶胶增加了海洋云的亮度和寿命”，第二段第二句对其进行了描述，但第二句描述的是增加了低位海洋云层的亮度和寿命，所以C选项也不正确。D选项是对第二段第一句的曲解，第二段第一句指出气溶胶通过对户外光线的散射来冷却海洋表面空气，而D选项指出通过聚集户外光线来冷却海洋表面空气。所以D选项也不正确。
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