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【填空答案】
climatic: adj. connected with the weather in a particular area 氣候的
iceage: one of the long periods of time, thousands of years ago, when ice covered many northern countries 冰川期，冰河時代
consistent: adj. always having the same beliefs, behavior, attitudes, quality etc（信仰、行為、態(tài)度、品質(zhì)等）一貫的，一致的；始終如一的
disturb: v. to interrupt someone so that they cannot continue what they are doing by asking a question, making a noise etc 干擾，打擾；使中斷
radiate: v. if something radiates light or heat, or if light or heat radiates from something, it is sent out in all directions 輻射（光或熱）；（向四面八方）發(fā)射
crude: adj. not developed to a high standard or made with great skill 粗制的
approximation: n. ［C］a number, amount etc that is not exact, but is almost correct 概算，近似值
hypothesis: n. ［C］pluralhypotheses, an idea that is suggested as a possible way of explaining a situation, proving and idea etc, which has not yet been shown to be true 假設，假說
speculate: v. to think or talk about the possible causes or effects of something without knowing all the facts or details 猜測，推測
disperse: v. if something disperses or is dispersed, it spreads over a wide area（使）消散；（使）分散
cooling: n.［U］the process of becoming cooler; a falling temperature 冷卻
【聽力原文】
Today I want to talk about the Earth's last major climatic shift, at the end of the last ice age.
But first, let's back up a moment and review what we know about climatic change in general. First,
we defined "climate" as consistent patterns of weather over significant periods of time.
In general, changes in climate occur when the energy balance of the Earth is disturbed. Solar
energy enters the Earth's atmosphere as light and is radiated by the Earth's surface as heat. Land,
water, and ice each affect this energy exchange differently. The system is so complex that, to date,
our best computer models are only crude approximations and are not sophisticated enough to test
hypotheses about the causes of climatic change.
Of course, that doesn't keep us from speculating. For instance, volcanic activity is one mechanism
that might affect climatic change. When large volcanoes erupt, they disperse tons of particles into
the upper atmosphere, where the particles then reflect light. Since less light is entering the system
of energy exchange, the result would be a cooling of the Earth's surface.
Of course, this is just one possible mechanism of global climate change. In all probability,
a complete explanation would involve several different mechanisms operating at the same time.
