Is Earth Getting Darker?
The sun is not growing weaker, yet its light appears to be dimming. Between 1960 and 1990, some scientists believe, the amount of solar radiation reaching Earth's surface may have declined as much as 10%--and in some places, Hong Kong, for example, more than 35%.
What was going on? Well, it appears that increased air pollution during those 30 years--over Asia, in particular--with the help, perhaps, of some increased cloudiness, may have exerted a cooling influence on the surface of the planet even as carbon dioxide and other greenhouse gases were encouraging the atmosphere to warm. The impacts of that tug-of-war on the climate system could be devilishly difficult to untangle. At the same time, no task could be more urgent. For if global pollution has helped keep global warming in check, says Veerabhadran Ramanathan, an atmospheric scientist at the University of California at San Diego, then the full impact of the buildup of greenhouse gases has yet to be felt. This week, at the American Geophysical Union meeting in Montreal, Ramanathan and others will be presenting the latest data on the solar-dimming problem and pondering its implications for the climate system as a whole.
Many scenarios for global warming, for example, invoke a speedup in the hydrological cycle by which water evaporates and then comes down as rain. The cooling produced by solar dimming, however, may slow the rate of evaporation, while higher up in the atmosphere the pollutants responsible for absorbing and reflecting sunlight are likely to interfere with the process that produces rain.
Why? These pollutants, which take the form of tiny, airborne particles called aerosols, act as nuclei around which cloud droplets form. The problem is, there are too many aerosols in the atmosphere competing for water molecules, so the cloud droplets that form are too small and never become weighty enough to fall to the ground. As a result, says Beate Liepert, an atmospheric physicist at Columbia University's Lamont-Doherty Earth Observatory, the atmosphere could be filled with moisture while Earth's surface thirsts for rain.
Many questions remain, including the true extent of the dimming. One analysis pegs the average worldwide darkening to be about 4% over three decades, while another computes it to be more than twice that much. There are also questions about the reliability of the devices that measure the sunlight reaching Earth's surface. Known as radiometers, these instruments are nothing more than flat, black solar collectors capped with glass. They are sometimes finicky; a smudge of dirt or a speck of dust can cause bogus readings and change the calculated results.
Solar dimming, in other words, is a problem still in the process of being defined, and as its dimensions become clearer, so will the nature of the challenge the world faces. Although scientists have done a lot of thinking about global warming, they are just beginning to grapple with the problem of how global warming and solar dimming interact. As Ramanathan puts it, "It's like we have a new gorilla sitting down at the table"--and it could turn out to be a very big gorilla indeed.
注（1）：本文選自Time; 5/24/2004, p60-60, 2/3p；
注（2）：本文習題命題模仿對象2004年真題Text 3；
1. By 「tug-of-war」(Line 4, Paragraph 2), the author means _________.
[A]the different effect of solar dimming and global warming
[B]the impact of the solar dimming on the climate system
[C]the influence of the solar dimming on the global warming
[D]the interaction between the solar dimming and global warming
2. How do the scientists feel about the current climate situation?
[A]Serious.
[B]Optimistic.
[C]Carefree.
[D]Panicked.
3.When mentioning 「It's like we have a new gorilla sitting down at the table」(Last Line,
Paragraph 6), the author implies that __________.
[A]scientists should have a close look at the solar dimming problem
[B]we are facing a new problem which is very complicated and difficult to manage
[C]we are just beginning to have research on this new field
[D]the new solar dimming problem is beyond scientists』 ability to tackle
4. Which of the following cannot serve as a factor of causing the cooling surface of the
planet?
[A]The lack of the rain in the earth.
[B]The increasing of the pollutants.
[C]The forming of the cloud droplets.
[D]The less weight of the cloud droplets.
5. Which of the following is true according to the text?
[A]The instruments used in the study are too simple to function well.
[B]Living things in the earth will be greatly influenced by solar dimming.
[C]There is still a long way to go in the study of solar dimming.
[D]The findings that solar dimming has influence on the surface of the planet are doubtful.
答案：DABAC
篇章剖析
本文是一篇類似科普的文章，採用提出問題——分析問題的模式，指出太陽變黯和全球變暖之間的相互作用和影響，並指出這一領域的研究存在的一些問題以及目前的研究水平。第一段指出太陽變黯這一現象；第二段、三段和四段分析產生這一現象的原因；第五段指出這一研究存在的一些問題；第六段指出目前的研究狀況。
詞彙注釋
cloudiness n. 雲量，雲度，朦朧；陰暗；混濁性，濁度
the tug-of-war拔河；擺花架子；兩派間激烈的競爭
devilish [5devElIF]adj. 魔鬼似的魔鬼的，似魔鬼的或魔鬼特性的；惡毒的；邪惡的；過分的；激進的
devilishly adv. 極度地；非常
untangle[ 9Qn`tAN^l ] vt. 解脫；澄清；解決；解開把…從一團糾結的事物中解脫出來；解開…的纏結；理清(某個讓人迷惑或複雜難解的事物)
hold [keep] in check 抑制, 約束, 制止, 牽制
scenario [sI5nB:rIEJ] n. 情況；劇情，構思；設想；方案
invoke [in5vEuk] vt. 向神靈祈求保佑; 用符咒召喚(魔鬼)；行使(法權等); 援引(法規、條文等)；請求; 懇求(援助等)；引起, 產生
hydrological adj. 水文(學)的
responsible for造成...的原因；歸因於…
take the form of 採取...的形狀; 表現為...的形式
aerosol [5eErEsRl] n. 懸浮微粒
act as vt.充當，扮演...的角色，作為
thirst vi. 渴, 想喝；渴望, 熱望(after, for)
peg vt. 用木釘[短樁]釘牢[固定](down, in, out); [主英]用木夾把(洗的衣服)夾在曬衣繩上；用木樁標出界線；拋、扔(東西)；固定, 限定; 穩定(工資, 價格, 市價); 鑑定, 認定；以...為題而寫
radiometer [9reidi5CmitE] n. 【物】輻射計; 射線測定器
finicky [5fInIkI] adj. 苛求的；過於講究的; 過分挑剔的，吹毛求疵的
smudge [smQdV] n. 汙點, 汙跡
speck [spek] n. 微粒；斑點；點
bogus [5bEu^Es] adj. [美] 假的, 偽造的
grapple with vt. 用...抓牢；與...搏鬥；盡力克服，設法解決
難句突破
Well, it appears that increased air pollution during those 30 years--over Asia, in particular--with the help, perhaps, of some increased cloudiness, may have exerted a cooling influence on the surface of the planet even as carbon dioxide and other greenhouse gases were encouraging the atmosphere to warm.
主體句式：it appears that …
結構分析：本句是一個賓語從句，其中「well」是一個語氣詞；賓語從句的主語是「increased air pollution」，其中「increased」是形容詞；「over Asia, in particular」的作用是補充說明；「with the help, perhaps, of some increased cloudiness」是介詞短語，用來補充說明主語；「even as」的意思是「正當...的時候；恰在...的時候」，用在本句中有一種對比的作用。
句子譯文：在過去30中，全球——特別是亞洲——不斷加劇的大氣汙染，藉助數量有所增加的雲度可能對整個地球表面起了一種冷卻作用，同時二氧化碳和其它溫室氣體卻在促使大氣變暖。
題目分析
1.答案為D，屬猜詞題。從句子「it appears that increased air pollution during those 30 years--over Asia, in particular--with the help, perhaps, of some increased cloudiness, may have exerted a cooling influence on the surface of the planet even as carbon dioxide and other greenhouse gases were encouraging the atmosphere to warm.」我們可看出一方面空氣汙染物及其形成的雲層對地球表面有一種冷卻作用，另一方面二氧化碳和其它溫室氣體卻促使大氣變暖。這是一種相互作用，一方強，另一方就弱，就像是「拔河賽」。文章最後一段的一句話「they are just beginning to grapple with the problem of how global warming and solar dimming interact」可以進一步印證我們的這一判斷。
2.答案為A，屬情感態度。原文對應信息是「no task could be more urgent.」。注意含有比較級的否定式的理解，這句話的意思是「This task is the most urgent.」從這句話我們可看出氣候學家們對待此事的態度。
3.答案為B，屬推理判斷題。文章最後一段的中心思想是：對太陽變黯這一問題的研究還
只是剛剛開始，還有很多東西我們不了解。然後以拉曼納森（Ramanathan）的話結束全文。就此我們可判斷拉曼納森的話也應該是符合這段文章的中心大意的。
4.答案為A，屬事實細節題。原文對應信息是「it appears that increased air pollution during those 30 years--over Asia, in particular--with the help, perhaps, of some increased cloudiness, may have exerted a cooling influence on the surface of the planet」。這句話的意思是「全球——特別是亞洲——不斷加劇的大氣汙染，藉助數量有所增加的雲度可能對整個地球表面起了一種冷卻作用」，而在形成雲層的過程中由於「the cloud droplets that form are too small and never become weighty enough to fall to the ground」（所形成的雲狀水滴顯得又太小，永遠達不到足以落到地面的重量），所以這些雲層無法變成雨滴落在地面，而是停留在大氣層，從而對大氣層起到一種冷卻作用。選項A是這種現象所造成的結果。
5.答案為C，屬推理判斷題。文章最後一段提到對太陽變黯這一問題的研究還只是剛剛開始，還有很多東西我們不了解。由此我們可做出判斷。
參考譯文
地球變得越來越暗了嗎？
太陽不是變得越來越弱，但太陽光似乎正變得越來越黯淡。有些科學家認為，從1960年到1990年，到達地球表面的太陽輻射量可能下降了10%，而有些地方, 例如香港，下降了35%以上。
這是怎麼了？在過去30中，全球——特別是亞洲——不斷加劇的大氣汙染，藉助數量有所增加的雲度可能對整個地球表面起了一種冷卻作用，同時二氧化碳和其它溫室氣體卻在促使大氣變暖。要擺脫這種拔河式效應對氣候系統的影響是極其困難的。但同時，沒有別的什麼任務能比這更迫切的了。加州大學聖地牙哥分校的大氣科學家Veerabhadran Ramanathan說，如果全球性汙染有助於控制全球氣候轉暖這一現象，那麼，世人必將遭受溫室氣體堆積造成的全面影響。本周，在蒙特婁召開的美國地球物理聯盟會議上，Ramanathan和其它人士將向大會展示有關太陽變黯問題的最新數據，期望與會人士能認真考慮太陽變黯對整個氣候系統的實質性影響。
比如，全球變暖的許多情況加速了水藉以蒸發、隨後變成雨降下的水文循環周期。然而，太陽變黯所產生的冷卻作用也許會降低水的蒸發速度，而大氣層上部吸收和反射太陽光的汙染物很可能對雨產生的過程進行了幹預。
為什麼？這些表現為極其微小的氣載微粒(叫做懸浮微粒)形式的汙染物扮演核心角色，在它周圍形成微小的雲狀水滴。問題是，大氣層中有太多的爭搶水分子的懸浮微粒，因此，所形成的雲狀水滴顯得又太小，永遠達不到足以落到地面的重量。哥倫比亞大學拉蒙-多爾蒂地球觀測所的大氣物理學家比特•利伯特說，因此，儘管大氣層可能充滿了溼氣，但地球表面卻乾燥無比，渴望下雨。
許多問題——包括太陽變黯的真實程度——尚無解決方案。一位分析人員認定，在過去約三十年中，世界範圍太陽平均變暗的程度為4%，而另一位分析人員估計變暗的程度超過此數的兩倍。測量到達地球表面陽光的設備是否可靠也是一個問題。測量陽光的儀器叫做射線測定器。這些儀器無非是一些罩著玻璃的黑色平板太陽能收集器。這些太陽能收集器有時過分挑剔：一塊小小的汙跡或一點點灰塵都可能造成虛假讀數，改變計算結果。
換句話說，太陽變黯仍然是一個尚處在定義過程中的問題，因此，隨著其輪廓變得越來越清晰,世界所面臨挑戰的性質也會變得愈加清晰可見。雖然科學家們對全球氣候變暖進行了大量的研究和思考，但他們也只是剛剛開始著手解決全球氣候變暖與太陽變黯如何相互作用的問題。正如Ramanathan所說，「這就像我們讓一個新來的大猩猩在餐桌旁就座的情形一樣。」 ——人們發現它確實是一個非常大的大猩猩。