四、阅读理解
Against the supposition(推测) that forest fires in Alaska, Canada and Siberia warm the climate, scientists have discovered that cooling may occur in areas where burnt trees allow more snow to mirror more sunlight into space.
This finding suggests that taking steps to prevent northern forest fires to limit the release of greenhouse gases may warm the climate in northern regions. Usually large fires destroyed forests in these areas over the past decade. Scientists predict that with climate warming, fires may occur more frequently over the next several centuries as a result of a longer fire season. Sunlight taken in by the earth tends to cause warming while heat mirrored back into space tends to cause cooling.
This is the first study to analyze all aspects of how northern fires influence climate. Earlier studies by other scientists have suggested that fire in northern regions speed up climate warming because greenhouse gases from burning trees and plants are released into the atmosphere and thus trap heat. Scientists found that right after the fire, large amounts of greenhouse gases entered the atmosphere and caused warming. Ozone(臭氧) levels increased, and ash from the fire fell on far-off sea ice, darkening the surface and causing more radiation from the sun to be taken in. The following spring, however, the land within the area of the fire was brighter than before the fire because fewer trees covered the ground. Snow on the ground mirrored more sunlight back into space, leading to cooling.
We need to find out all possible ways to reduce the growth of greenhouse gases in the atmosphere. Scientists tracked the change in the amount of radiation entering and leaving the climate system as a result of the fire, and found a measurement(测量法) closely related to the global air temperature. Typically, fire in northern regions occurs in the same area every 80 to 150 years. Scientists, however, found that when fire occurs more frequently, more radiation is lost from the earth and cooling results. Specifically, they determined when fire returns 20 years earlier than predicated, 0.5 watts per square meter of area burned are soaked up by the earth from greenhouse gases, but 0.9 watts per square meter will be sent back into space. The net effect is cooling. Watts are used to measure the rate at which energy is gained or lost from the earth.
()1. According to the new findings, taking steps to prevent northern forest fires may .
A. result in a warming climate
B. cause the forest fires to occur more frequently
C. lead to a longer fire season
D. protect the forests and the environment there
()2. The following are all the immediate effects after a forest fire EXCEPT .
A. large amounts of greenhouse gases enter the atmosphere
B. the levels of ozone which is a type of oxygen increase
C. snow on the ground mirrors more sunlight back into space
D. ashes from the fire fall on the ice surface and take in more radiation from the sun
()3. Earlier studies about northern forest fires .
A. analyze all aspects of how northern fires influence climate
B. indicate that forest fires will pollute the atmosphere
C. suggest that people should take measures to protect the environment
D. suggest that the fires will speed up climate warming
()4. From the passage we can draw a conclusion that forest fires in Alaska, Canada and Siberia may .
A. warm the climate as the supposition goes
B. allow more snow to reflect more sunlight into space and thus cool the climate
C. destroy large areas of forests and pollute the far-off sea ice
D. help to gain more energy rather than release more energy

1.A 2.C 3.D 4.B
【语篇解读】本文是一篇说明文。文章主要说明了发生在阿拉斯加、加拿大和西伯利亚这些地球北部的大火对当地气候所产生的影响:大火过后,覆盖地面的树木变少,这让来年更多的雪将更多的阳光反射进太空而使得气温变低。
1. A 解析:细节理解题。根据第二段中的“This finding suggests that taking steps to prevent northern forest fires to limit the release of greenhouse gases may warm the climate in northern regions.”可知,采取这样的措施最终可能导致北部地区的气候变暖。故选 A。
2. C 解析:推理判断题。根据第三段中的“The following spring however, the land within the area of the fire was brighter than before the fire because fewer trees covered the ground. Snow on the ground mirrored more sunlight back into space, leading to cooling.”可知,地上的雪反射更多的阳光是在第二年春天发生的事情,这是大火的间接影响,并不是 immediate effects(直接影响)。故选 C。
3. D 解析:细节理解题。根据第三段中的“Earlier studies by other scientists have suggested that fire in northern regions speed up climate warming because greenhouse gases from burning trees and plants are released into the atmosphere and thus trap heat.”可知,早期研究表明,火灾会加速气候变暖。故选 D。
4. B 解析:细节理解题。根据第一段中的“Against the supposition that forest fires in Alaska, Canada and Siberia warm the climate, scientists have discovered that cooling may occur in areas where burnt trees allow more snow to mirror more sunlight into space.”可知,从这个研究中得到的结论是,这些地区的山火让更多的雪将更多的阳光反射到太空中,从而使气候变凉。故选 B。