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El Nino has for centuries been a regular, if somewhat reckless, climatic event. It typically makes its presence felt around midwinter, hence a name that loosely translates as “Christ child” in the Spanish of the Peruvian fishermen who first noticed it. El Nino begins, however, some months prior to that, when trade winds in the western tropical Pacific drop or even shift, switching from blowing westward to the east. When this happens, a body of warm water that normally pools in the ocean east of Australia begins to move toward the coast of Peru. Warm air rising from the surface of this mass—which is as much as 12 F warmer than normal acts like a paddle stuck into the southern jet stream, redirecting it northward and altering weather from Australia to Canada to Africa. The warm water itself, meanwhile, is like a cap on a bottle when it hits the coast of Peru, halting the rise of cold, nutrient-rich water that typically emerges along the South American coast from deep in Pacific. That drastically affects the food chain for marine mammals, birds and fish.

Scientists have grown steadily more familiar with El Nino in the past 20 years. “There’s been a fundamental change since the 1982-1983 El Nino,” the devastating event the 1997-1998 El Nino surpassed in size, says McPhaden. “We didn’t even know that one was happening until it was almost over. In the 1997-1998 El Nino, we could tell you day by day what was happening.” The reason? Two new powerful tools—instrumented satellites and buoys—now make it as easy for scientists to watch the ocean as if it were a wading pool in their backyard.

Still, scientists were disappointed by one significant aspect of the past year’s work on El Nino: their ability to forecast it accurately. While a few computer models suggested that an El Nino would develop in 1997, none came close to predicting its scope or the speed with which it developed. Even the gold standard of forecasting turned into lead. A model developed by Mark Cane and Steven Zebiak was considered the best among El Nino forecasting models. But it didn’t read the global tea leaves correctly, forecasting an El Nino that was much later and smaller than the one that actually hit.

单选题 According to the article, what is not true about El Nino?
【正确答案】 D
【答案解析】根据第一段第二句“It typically makes its presence felt around midwinter…”可知A正确。 根据第一段第三句“El Nino begins, however, some months prior to that…”可知B正确。 根据第一段最后一句“That drastically affects the food chain for marine mammals, birds and fish.”可知C正确。 而D项文中未提及， 因此选D。
单选题 When El Nino occurs, _____.
【正确答案】 A
【答案解析】本题可根据排除法选出。 首先并没有在文中找到有力的反驳A项的句子。 而根据第一段“Warm air rising from the surface of this mass—which is as much as 12 F warmer than normal…”这里的which是来修饰“the mass”也就是前文的“warm water”的， 因此不是暖空气的温度比平时高， 排除B。 再根据“…switching from blowing westward to the east.”可知该现象发生时， 季风从向西转向向东吹， 排除C。 又根据“…altering weather from Australia to Canada to Africa.”可知气候变化是从澳洲到非洲依次变化的， 排除D。 因此选A。
单选题 What’s the fundamental change since 1982-1983 El Nino?
【正确答案】 A
【答案解析】根据第二段“In the 1997-1998 El Nino, we could tell you day by day what was happening.”可知以前人们几乎不会察觉厄尔尼诺现象的发生， 而现在通过卫星和浮标， 科学家们对这个现象更为熟悉。 因此选A。
单选题 Concerning the prediction of El Nino, which statement is not true?
【正确答案】 D
【答案解析】由最后一段“none came close to predicting its scope or the speed with which it developed.”可知， 人类无法准确的预测出厄尔尼诺现象的范围和威力。 因此选D。
单选题 The prediction for 1997-1998 El Nino failed, because _____.
【正确答案】 B
【答案解析】根据最后一段“While a few computer models suggested that an El Nino would develop in 1997, none came close to predicting its scope or the speed with which it developed.”可选出答案。