Soot and Sow：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.
詞彙：
soot n.煤煙，煤灰 emission n.釋放，散發，排放
simulation n.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
註釋：
h指代albedo。
heating the snow surface more than if there were no black carbon：相當於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。
rest：剩餘部分
cover：雪的覆蓋層
練習：
graph 3 ________
graph 4 ________
graph 6 ________
graph 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
the twentieth century, soot ________.
en cautioned that greenhouse gases ________.
k 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 第三段解釋了為什麼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係方面取得的成果。
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，因為第五題的題幹中有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.
譯文：煤灰與白雪：“火熱"的組合
美國國家航空航天局的科學家的一項新調查顯示，黑色煤煙的排放改變了冰雪對陽光的.反射。依據電腦模擬，上世紀觀測到的的全球變暖有25%是黑煤灰引起的。
地球高緯地區冰雪覆蓋，那裡的煤灰比白色的冰面吸收了更多的太陽熱能。因為深黑色的炭或煤灰吸收太陽光，而淺色的冰面則反射陽光。
冰雪地區的煤灰對氣候變化可能起著至關重要的作用。而且一旦覆蓋大地的冰雪開始融化，煤灰就會更加固著於冰面，從而加劇溫室效應。“冰山、冰塊一融化，就會變得更髒，”James Hansen博士，一位來自紐約美國國家航空和航天局的Goddard太空研究所的研究人員如此說。
Hansen發現，煤灰對冰雪反射率的影響，可能正是促使北半球春季提早的原因，引起北冰洋冰層變薄，冰山及凍土雪原融化。據信煤灰對海洋和陸地上空大氣層的變化也有一定影響。
“黑炭減少了冰雪反射回太空的能量，比沒有炭灰的條件下更強烈地加熱冰面。”Hansen說。煤灰對太陽熱能的大量吸收是全球氣候變暖的重要因素。Hansen指出，“這種溫室作用特別顯著，是同量二氧化碳強度的兩倍。”
Hansen又提醒說，儘管煤灰對全球氣候變化的作用重大，但這並不能改變一個事實：溫室氣體是上世紀氣候變暖的首要原因，而且它們還將是塑造本世紀氣候的主力。
研究人員發現北半球觀測到的變暖現象大多發生在中高緯地區的冬春兩季。這樣的觀測結果與氣象模擬實驗相吻合，表明部分大規模的溫室效應發生在有厚雪覆蓋層和陽光強烈的時期。
