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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 does the word "nascent" (Para. 3) mean?
选项 A、Powerful.
B、Earlier.
C、Horrible.
D、Small.
答案B
解析 回归到第三段第三句，This extra wind shear tears nascent storms apart before they can gain strength。they指的是storms。在风暴变强大前，也就是在风暴还处于形成初期的状态下就将其切断，所以nascent的同义词是B。该题容易误选成D选项small，但该句并没有明确表示风暴的大小，而是说在它形成的初期和力量增强前。
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