Soot and Snow: A Hot Combination

1　New research from NASA scientists suggests emissions of black soot alter the way sunlight reflects off snow. According to a computer simulation, black soot may be responsible for 25 percent of observed global warming over the past century.

2　Soot in the higher latitudes of the Earth, where ice is more common, absorbs more of the sun’s energy and warmth than an icy, white background. Dark-colored black carbon, or soot, absorbs sunlight, while lighter colored ice reflects sunlight.

3　Soot in areas with snow and ice may play an important role in climate change. Also, if snow and ice covered areas begin melting, the warming effect increases, as the soot becomes more concentrated on the snow surface. “This provides a positive feedback, as glaciers and ice sheets melt, they tend to get even dirtier, said Dr. James Hansen, a researcher at NASA’s Goddard Institute for Space Studies, New York.

4　Hansen found soot’s effect on snow albedo（solar energy reflected back to space），which1 may be contributing to trends toward early springs in the Northern Hemisphere, such as thinning Arctic sea ice, melting glaciers and permafrost. Soot also is believed to play a role in changes in the atmosphere above the oceans and land.

5　“Black carbon reduces the amount of energy reflected by snow back into space, thus heating the snow surface more than if there were no black carbon2，” Hansen said. Soot’s increased absorption of solar energy is especially effective in warming the world’s climate. “This forcing is unusually effective, causing twice as much global wanning as a carbon-dioxide forcing of the same magnitude, Hansen noted.

6　Hansen cautioned, although the role of soot in altering global climate is substantial, it does not alter the fact that greenhouse gases are the primary cause of climate warming during the past century.3 Such gases are expected to be the largest climate forcing for the rest4 of this century.

7　The researchers found that observed warming in the Northern Hemisphere was large in the winter and spring at middle and high latitudes. These observations were consistent with the researchers’ climate model simulations, which showed some of the largest warming effects occurred when there were heavy snow cover5 and sufficient sunlight.

注釋：

1．which指代albedo。

2．thus heating the snow surface more than if there were no black carbon：相當于thus heating the snow surface more than（heating the snow surface）if there were no black carbon。

3．... the fact that greenhouse gases are the primary cause of climate warming during the past century：“that greenhouse gases ... during the past century”是同位語從句，表達fact的內容。

4．the rest：剩余部分

5．snow cover：雪的覆蓋層

練習：

1．Paragraph 3 ________

2．Paragraph 4 ________

3．Paragraph 6 ________

4．Paragraph 7 ________

A　Soot’s Role in Changes in the Climate and the Atmosphere

B　Observations of Warming in the Northern Hemisphere

C　Explanation of Increased Warming Effect Caused by Soot

D　Effort to Reduce Snow Albedo

E　Ways to Reduce Soot Emission

F　Greenhouse Gases as the Main Factor of Global Warming

5．In the twentieth century, soot ________.

6．Hansen cautioned that greenhouse gases ________.

7．Black soot covered snow and ice ________.

8．A soot forcing is unusually effective, which ________.

A　produces much more global wanning than a carbon-dioxide forcing of the same magnitude

B　continued to 25 percent of observed global warming

C　can produce greenhouse gases

D　absorb more of sun’s energy and warmth than white background

E　still surpass soot in warming the world’s climate during the last centry

F　can be seen mostly in the Northern Hemisphere

答案與題解：

1．C　第三段解釋了為什么soot會增加地球升溫效應。

2．A　第四段介紹了soot在兩方面起的作用：（1）soot增加了雪吸收太陽能量和熱量的能力；（2）soot導致海洋和陸地上空的大氣層發(fā)生變化。

3．F　第六段的關鍵句子是：“... greenhouse gases are the primary cause of climate warming during the past century.”

4．B　第七段介紹了在研究北半球的緯度、雪覆蓋面和日照諸因素與氣溫升高之間的關系方面取得的成果。

5．B　選擇B的依據是第一段。有關的句子是：“... black soot may be responsible for 25 percent of observed global warming over the past century.”選項B中用了過去式contributed，也是選B的一個線索，因為第五題的題干中有in the twentieth century，這個時間狀語要求謂語動詞用過去式，而4個選項中只有B項的動詞用的是過去式。

6．E　Hansen cautioned和greenhouse gases僅出現在第六段。該段的大意是：雖然煤煙在改變全球氣候方面所起的作用相當顯著，但是上個世紀氣溫上升的主要因素還是溫室氣體。選項E概括了第六段的意思。

7．D　本題答案的依據是第二段第一句。

8．A　本題答案的依據是第五段的下列句子：Soot’s increased absorption of solar energy is especially effective in warming the world’s climate. “This forcing is unusually effective, causing twice as much global warming as a carbon-dioxide forcing of the same magnitude，” Hansen noted.

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