Question

    The argument that human-caused carbon emissions(排放) are merely a drop in the bucket compared to greenhouse gases generated by volcanoes has been making its way around the rumor mill for years. And while it seems to be reasonable, the science just doesn't back it up.

According to the US Geological Survey (USGS), the world's volcanoes, both on land and undersea, generate about 200 million tons of carbon dioxide (CO₂) annually, while our automotive and industrial activities cause some 24 billion tons of CO₂ emissions every year worldwide. Despite the arguments to the contrary, the facts speak for themselves: Greenhouse gas emissions from volcanoes compose less than one percent of those generated by today's human activities.

Another indication that human emissions surpass those of volcanoes is the fact that atmospheric CO₂ levels, as measured by sampling stations around the world, have gone up consistently year after year regardless of whether or not there have been major volcanic eruptions in specific years. “If it were true that individual volcanic eruptions dominated human emissions and were causing the rise in carbon dioxide concentrations, then these carbon dioxide records would be full of spikes —one for each eruption,” says Coby Beck, a journalist writing for online environmental news. “Instead, such records show a smooth and regular trend.”

Furthermore, some scientists believe that volcanic eruptions, like that of Mt.St. Helens in 1980 and Mt. Pinatubo in 1991, actually lead to short-term global cooling, not warming, as sulfur dioxide (SO₂), ash and other particles in the air and stratosphere(平流层) reflect some solar energy instead of letting it into Earth's atmosphere. SO₂, which converts to sulfuric acid aerosol, when it hits the stratosphere, can linger there for as long as seven years and can exercise a cooling effect long after a volcanic eruption has taken place.

Scientists tracking the effects of the major 1991 eruption of the Philippines’ Mt. Pinatubo found that the overall effect of the blast was to cool the surface of the Earth globally by some 0.5 degrees Celsius a year later, even though rising human greenhouse gas emissions and an El Nino event caused some surface warming during the 1991-1993 study period.

In an interesting twist on the issue, British researchers last year published an article in the peer reviewed scientific journal Nature showing how volcanic activity may be contributing to the melting of ice caps in Antarctica but not because of any emissions, natural or man-made. Instead, scientists Hugh Corr and David Vaughan of the British Antarctic Survey believe that volcanoes underneath Antarctica may be melting the continents ice sheets from below, just as warming air temperatures from human-induced emissions erode them from above.

1.According to Paragraph 1, some people argue that   .

A.their opinion is supported by science.

B.volcanoes generate most of the greenhouse gases.

C.human activities are to blame for greenhouse gases.

D.carbon emissions produced by volcanoes are increasing.

2.What does the underlined word “spikes" in Paragraph 3 probably mean?

A.Sudden increases. B.Smooth trends.

C.Stable regularities. D.Sharp declines.

3.What do the scientists mentioned in this passage believe about volcanic eruptions?

A.They brought about global warming.

B.They actually partly cooled the surface of the Earth.

C.They melted the ice sheets in Antarctic from above.

D.They dominated human emissions in greenhouse effect.

4.The purpose of the passage is to   .

A.compare the results of the studies.

B.contradict a view held by some people.

C.present new findings for greenhouse phenomenon.

D.report the effects of CO₂, in greenhouse phenomenon.

Answer

1.B

2.A

3.B

4.B

【解析】

本文为议论文。文章用事实来反驳多年来人们认为火山产生了大部分的温室气体的观点。证实了火山不仅没让地球变暖，而是一定程度上导致全球温度下降，起到冷却作用。

1.推理判断题。根据第一段“The argument that human-caused carbon emissions(排放) are merely a drop in the bucket compared to greenhouse gases generated by volcanoes has been making its way around the rumor mill for years.” 多年来，与火山产生的温室气体相比，人类造成的碳排放量只占很小的论调一直在坊间流传。由此可推断出，一些人认为是火山产生了大部分的温室气体。故选B。

2.猜测词义题。第三段的内容：根据世界各地采样站的测量表明人类排放量超过火山排放量的一个迹象是大气中的二氧化碳水平年复一年地持续增加，而不管特定年份是否发生过重大的火山喷发。根据划线词的If it were true that individual volcanic eruptions dominated human emissions and were causing the rise in carbon dioxide concentrations, then these carbon dioxide records would be full of spikes —one for each eruption,” says Coby Beck, a journalist writing for online environmental news. “Instead, such records show a smooth and regular trend.”可知“如果个别火山爆发时二氧化碳高于人类的排放，并导致二氧化碳浓度的增加，那么每一次火山喷发都会充满“spikes”，相反的是，记录显示出二氧化碳浓度增加是“平稳而有规律的”。 句中的“instead”表示转折，表示前后意思相反。环境新闻的记者Coby Beck说二氧化碳浓度的增加“记录显示出平稳的”，那么，“spikes”应该就是与之相反的“突然”的增加。分析选项A. Sudden increases突然增加；B. Smooth trends平稳的趋势； C. Stable regularities稳定的规律；D. Sharp declines急剧下降。可知，A项符合题意，故选A。

3.细节理解题。根据第四段“some scientists believe that volcanic eruptions, like that of Mt.St. Helens in 1980 and Mt. Pinatubo in 1991, actually lead to short-term global cooling, not warming”一些科学家认为，火山喷发，像在1980和1991的火山爆发，实际上在短期内导致短期全球冷却，而不是变暖。由此可知，火山实际上在一定程度上冷却了地球表面。分析选项可知B项符合题意，故选B。

4.推理判断题。本文第一段提出：多年来，人们认为与火山产生的温室气体相比，人为碳排放只是沧海一粟，非常小， 但在科学上却是错误的。接着下文对此进行批判的同时提出了新的发现，即火山的爆发却能一定程度地导致全球温度下降，起到冷却作用。即反驳了某些人的观点。这篇文章的目的是反驳一些人所持的观点。故选B。