It may have become the penance of choice for the environmentally conscious individual, but planting trees to offset carbon emissions could contribute to global warming if they are planted outside the tropics, scientists believe.
They argue that most forests do not have any overall effect on global temperature but, by the end of the century, forests in the mid and high latitudes could make their parts of the world more than 3℃ warmer than would have occurred if the trees did not exist.
Govindasamy Bala, an atmospheric scientist at the Lawrence Livermore Laboratory in the US, has shown that only tropical rainforests are beneficial in helping slow global warming. The problem is that while the carbon dioxide forests use for photosynthesis indirectly helps cool the Earth by reducing the amount of greenhouse gases in the atmosphere, forests also trap heat from the sunlight they absorb.
Dr.Bala and his colleague, Ken Caldeira of the department of global ecology at the Carneige Institute in Standford, used a computer model to show that, outside a thin band around the equator, forests end up trapping more heat than they help to get rid of through a cut in carbon dioxide. Planting trees above 50 degrees latitude—the equivalent of Scandinavia or Siberia in the northern hemisphere—also cover up tundra normally blanketed in heat-reflecting snow.
The scientists said that the results, published yesterday in the Proceedings of the National Academy of Scientists, are explained by the way in which the sun’s rays are absorbed or reflected by different parts of the world. Forest canopies, being relatively dark, absorb most of the sun’s heating rays that fall on them, warming the surface of the Earth all around. In contrast, grassland or snowfields reflect a lot more of the sun's rays back into space, keeping temperatures in open areas lower.
Dr.Bala said that trees at lower latitudes have a dual role. 「 It is a win-win situation in the tropics because trees in the tropics, in addition to absorbing carbon dioxide, promote convective clouds that help to cool the planet. In other locations, the warming from the albedo effect (the amount of sunlight reflected back into space) either cancels or exceeds the net cooling from the other two effects.」
The results follow increasing criticism from climate scientists of the benefits of forestry schemes to offset carbon emissions. Kevin Anderson, a scientist with the Tyndall Centre for Climate Change Research, warned recently that offsetting was a dangerous delaying technique that helped people 「sleep well at night when we shouldn't sleep well at night.」
1. According to the essay, which of the following statements is CORRECT?
A. Planting trees to offset carbon emissions would not have become the penance of choice for the environmentally conscious individual, if they were planted in the tropics.
B. Forests in the mid and high latitudes would have an effect on global temperature by the end of the century.
C. Though forests outside the tropics help cool the Earth directly by photosynthesis, the heat that they absorb from the sunlight will contribute to global warming.
D. Dr Bala and Ken Caldeira pointed out that forests end up trapping more heat than they get rid of through a cut in carbon dioxide.
2. According to the essay, what is not the effect of the tropical rainforests?
A. To reduce the amount of green house gases.
B. To help slow global warming.
C. To trap heat from the sunlight.
D. To promote convective clouds.
3. The 「Proceedings of the Nationa Academy of Scientists」 (Para.5)refers to .
A. a program
B. a magazine
C. learned news
D. scientific masterpiece
4. From the warning of Kevin Anderson, we can know that .
A. the forestry schemes will be effective to help cool earth
B. the global warming is hard to be controlled
C. the offsetting will mainly contribute to global warming
D. people will suffer from the global warming
5. We cannot learn from the essay that .
A. if the trees are planted outside the tropics, the forestry schemes could contribute to global warming
B. some researches have shown that tropical rainforests are beneficial in helping slow global warming
C. if we want to slow global warming, we should see the forestry schemes from two sides and improve the harmful part
D. offsetting can not help to cool the planet effectively
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penance [ˈpenəns]
n. 懺悔，苦修
vt. 使……以苦行贖罪
promote [prəˈməʊt]
vt. 促進，發揚，提升，提拔，晉升為
conscious [ˈkɒnʃəs]
adj. 有意識的，有知覺的，故意的，羞怯的
cancel [ˈkænsl]
vt. 取消，刪去
dioxide [daɪˈɒksaɪd]
n. 二氧化物
global [ˈgləʊbl]
adj. 球形的，全球的，全世界的
photosynthesis [ˌfəʊtəʊˈsɪnθəsɪs]
n. 光合作用
latitudes ['lætɪtju:dz]
n. 緯度，範圍，（用複數）地區
canopy [ˈkænəpi]
n. 天篷，遮篷
dual [ˈdju:əl]
adj. 雙的，二重的，雙重
atmospheric [ˌætməsˈferɪk]
adj. 大氣的
convective [kən'vektɪv]
adj. 傳送性的，對流的
tropical [ˈtrɒpɪkl]
adj. 熱帶的，熱情的
absorb [əbˈsɔ:b]
vt. 吸收，吸引
albedo [æl'bɪdəʊ]
n. ［天文］（星體）反照率
equator [ɪˈkweɪtə(r)]
n. 赤道，赤道似的圓圈
forestry [ˈfɒrɪstri]
n. 林業，森林地，林學
1. It may have become the penance of choice for the environmentally conscious individual, but planting trees to offset carbon emissions could contribute to global warming if they are planted outside the tropics, scientists believe.
結構分析：本句是一個並列句。but連接前後兩個有轉折意義的分句；planting trees to offset carbon emissions是一個動名詞短語作主語；if後面引導一個條件狀語從句；而其中又包含被動結構 they are planted……。
參考譯文：對於有環保意識的人來說這可能是一個懺悔式的抉擇，但是，科學家認為，如果在熱帶以外的地區植樹，用植樹來抑制二氧化碳的排放反而會加劇全球變暖。
2. They argue that most forests do not have any overall effect on global temperature but, by the end of the century, forests in the mid and high latitudes could make their parts of the world more than 3℃ warmer than would have occurred if the trees did not exist.
結構分析：本句是一個並列句。but連接前後兩個有轉折意義的分句。that引導一個賓語從句，來作 argue的賓語；than would have occurred是一個than引導的省略句；後面跟一個if引導的條件狀語從句 if the trees did not exist。
參考譯文：他們指出，大多數的森林在控制全球氣溫方面沒有整體效應；但是到21世紀末，處於中高緯度地區的森林會使它們所處區域的氣溫比在沒有森林的地區高出三攝氏度。
3. Dr. Bala and his colleague, Ken Caldeira of the department of global ecology at the Carneige Institute in Standford, used a computer model to show that, outside a thin band around the equator, forests end up trapping more heat than they help to get rid of through a cut in carbon dioxide.
結構分析：本句是一個複合句。主句是Dr．Bala and his colleague... used a computer model to show；Ken Caldeira... of Standford作 his colleague的同位語；that引導一個賓語從句，作show的賓語，在這個賓語從句中，trapping more heat是現在分詞作狀語，表伴隨的狀態；than they help to... carbon dioxide. 是一個than引導的省略句，省略了of後的賓語heat。
參考譯文：巴拉博士和他史丹福大學全球生態學系的同事肯・卡爾代拉，通過計算機模擬顯示：環繞在赤道附近的很少的帶狀部分，森林產生的熱量最終將超過它們用來降低二氧化碳含量而減少的熱量。
4. The scientists said that the results, published yesterday in the Proceedings of the National Academy of Scientists, are explained by the way in which the sun’s rays are absorbed or reflected by different parts of the world.
結構分析：本句是一個複合句，主句是 The scientists said；that引導一個賓語從句作said的賓語；published yesterday... 是過去分詞短語作後置定語來修飾 the results；are explained by以及 are absorbed or reflected都是被動結構，in which作關係代詞引導一個定語從句，來修飾 the way。
參考譯文：科學家們指出，昨天刊登在美國科學協會彙刊上的結果可以用太陽光被世界上不同地方吸收或反射來進行解釋。
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