衛生類A級：概括大意Soot and Snow
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 all important role in climate change.Als0，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 sheet smelt，they tend to get even dirtier，” said Dr.James Hansen，a researcher at NASAs Goddard Institute for Space Studies，NewYork.
4 Hansen found soot’s effect on snow albedo(solar energy reflected back to space)，which 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 carbon~，”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 warming 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.Such gases are expected to be the largest climate forcing f10r也e rest of this century.
7 The researchers found that observed warming in the Northern Hemisphere was 1arge 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 cover and sufficient sunlight.
詞匯：
soot n.煤煙，煤灰
emission n.釋放，散發，排放
simulation v.模擬
latitude n.緯度
glacier n.冰川，冰河
albedo n.反照率
permafrost n.永凍層
forcing n.溫室作用
dioxide n.二氧化物
magnitude n.量，大小
練習：
1.Paragraph 3____________
2.Paragraph 4____________
3.Paragraph 6____________
4.Paragraph 7____________
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____________
參考答案:
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 me 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，”Harisen noted.