GMAT 讀新聞20180810

來自專欄 GMAT 學習

Will Dimming the Sun Cool the Planet and Help Crops?

Source: Science American

As [1]Earth』s temperature steadily climbs and international action to curtail heat-trapping greenhouse gases falters, climate change poses such a dire threat that scientists are now seriously investigating geoengineering as[2] a last-ditch attempt to cool the planet.

語法 『As』

第一句話中的as 表示伴隨，隨著; 第二句中的as 是介詞，意為「作為，當作」。

But deliberately manipulating Earth』s climate could obviously have unintended consequences, so 「it』s very important that we study it before anyone tries to use it,」 says Solomon Hsiang, a professor of public policy at the University of California, Berkeley. 「We should know what we』re getting ourselves into.」 Hsiang and a team of researchers aimed to find out with a new study that looks at how one type of proposed geoengineering—injecting tons of tiny particles into the atmosphere to deflect sunlight and shade the planet—would affect a very important system: agricultural crops.

語法

Idiom: aim to do something

破折號：破折號前的句子並不是完整的句子，所以左右兩邊都有破折號來完成整個句子。句子核心意思為…how one type of proposed geoengineering would affect a very important system: agricultural crops.破折號中的內容解釋了geoengineering 具體是要幹什麼。

A growing body of research suggests heat stress from global warming could crimp harvests—a major concern for global food security. For example, a study published in June found corn yields would drop overall and see more year-to-year variability as temperatures rise. Solar geoengineering, then, would seem like a potential way to ease the agrarian climate burden. It even offers the additional benefit of scattering the sun』s rays, creating the kind of diffuse light that many plants tend to prefer. But there is a potential snag: Plants would receive less light overall for photosynthesis. What remains unclear is which effect wins out, and so whether such geoengineering would ultimately hurt or help agriculture. Hsiang』s new study, published Wednesday in Nature, attempts to determine the overall effect.

Photosynthesis /,fotos?nθ?s?s/ 光合作用

破折號：破折號前的句子完整，單破折號。

這段話的內容比較豐富： 越來越多的研究顯示由溫室效應帶來的溫度增長有害於糧食產量，從而嚴重影響了全球食物安全。solar geoengineering被認為一種可以緩解氣溫增加對糧食作物的影響，但同時又有擔心它會有負面的因素，即較少的光照會影響植物的光合作用。那麼針對這個問題，科研團隊( Hsiang and his team) 進行了研究，試圖獲得solar geoengineering對糧食作物的綜合影響。文中提到開展了某種研究，那麼研究的成果將是決定文章主題的重要內容，是GMAT 閱讀需要抓住的重點。

Hsiang and his team used two massive volcanic eruptions—Mount Pinatubo in the Philippines in 1991 and Mexico』s El Chichón in 1982—as analogues for solar geoengineering. Both eruptions shot millions of tons of sulfur dioxide into the atmosphere, where[3] the gas became sulfate aerosols that blocked sunlight (somewhat akin to what solar geoengineering could do). Mount Pinatubo』s sulfate aerosols cooled the entire Earth by about 0.5 degree Celsius for almost two years.

語法

Comma+ where, 修飾緊前的atmosphere, where 只能用來修飾具體的空間。

The team analyzed global satellite data from both eruptions, along with crop yields for corn, soy, rice and wheat in 105 countries from 1979 to 2009. The researchers specifically wanted to measure how dimmed sunlight from the eruptions had influenced crop growth, so they calculated out the effects of other variables like rainfall. They found changes in sunlight due to Pinatubo had reduced crop yields whereas El Chichón caused less such harm (although that eruption was not as well measured as Pinatubo, a factor that could skew these findings). Pinatubo』s dimming effect cut global corn yields by an average of 9 percent, and soy, rice and wheat by 5 percent. The results were a surprise because scientists had expected the resulting light diffusion to be more beneficial for the crops, Hsiang says.

研究結果： pay close attention to the big results that are critical for you to understand the whole picture of the passage.

The team combined its historical analysis with a global climate model to predict crop yields on a future, hotter planet—with and without solar geoengineering. They found that with geoengineering the reduced sunlight decreased crop yields enough to offset any potential gains from cooler temperatures. 「We』re not saying that geoengineering harms agriculture on net. What we』re saying is that it doesn』t help agriculture,」 Hsiang says. 「Before us, many people had said that this could be a way to save agriculture—you could geoengineer the climate to prevent it from getting hot, so you don』t have crop failure. We point out that when you do that, you shift the crop losses from being caused by heat to being caused by [less] light.」

重申研究結果。

Some experts who were not involved in the study say its conclusions should be interpreted cautiously. 「This is a good effort, but we have a very limited amount of data over a limited time period to make these estimates,」 says Douglas MacMartin, a senior research associate in mechanical and aerospace engineering at Cornell University. 「One shouldn』t take the conclusions as, 『This is what would happen if we did solar geoengineering.』」 David Keith, a professor of applied physics at Harvard University, expressed deep skepticism about using volcanic eruptions as an analogue for the practice. 「Geoengineering would alter the climate in a very different way than the way a volcanic eruption does,」 he says. For one, geoengineering would involve a repeated infusion of aerosols, compared with the 「sudden shock」 of a volcanic eruption; that sustained presence of aerosols, he says, would create different cooling dynamics than the volcano and thus affect other aspects of the climate—such as precipitation—differently. Alan Robock, a professor of climate science at Rutgers University, also points out agricultural technology and techniques change over time. It』s not clear, he says, 「whether these results would be applicable in the future if we ever do geoengineering.」

Critical Reasoning:

這段話可以做為CR 學習的素材。 在很多學術報告中其實都會有這樣的內容，研究過程中哪些假設有不全面，或者研究方法有問題，得出對研究結果的質疑，這樣的質疑為進一步研究提供了線索。當然，在商業環境中，這樣的質疑，是進一步修正的基礎， 是必不可少的。不論是學術還是商業，都是面向未來的，沒有準確答案，只能不斷地去修正、改進或完善。

針對Hsiang的研究，其他科學家表示should be interpreted cautiously. 他們用了哪些argument 來削弱Hsiang 的論證呢？

Evidence not sufficient----There were very limited amount of data over a limited time period to make these estimates.

Questionable analogy----Geoengineering would alter the climate in a very different way than the way a volcanic eruption does

What happens today may not be true tomorrow---- Agricultural technology and techniques change over time

Despite their critiques, these independent experts acknowledge it is critical to conduct studies of geoengineering and its potential consequences. 「It is important to do this research so we understand and quantify all the risks. Some people argue you shouldn』t do this research. But we might find out that geoengineering is not a good solution at all,」 Robock says. 「The sooner we know that, then there might be a greater push to mitigate climate change—because we do not have a 『get out of jail free』 card.」

結論總是積極的~~

Passage Map: